2
/* pngwutil.c - utilities to write a PNG file
4
* Last changed in libpng 1.6.21 [January 15, 2016]
5
* Copyright (c) 1998-2002,2004,2006-2015 Glenn Randers-Pehrson
6
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7
* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
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* This code is released under the libpng license.
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* For conditions of distribution and use, see the disclaimer
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* and license in png.h
16
#ifdef PNG_WRITE_SUPPORTED
18
#ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
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/* Place a 32-bit number into a buffer in PNG byte order. We work
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* with unsigned numbers for convenience, although one supported
21
* ancillary chunk uses signed (two's complement) numbers.
24
png_save_uint_32(png_bytep buf, png_uint_32 i)
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buf[0] = (png_byte)(i >> 24);
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buf[1] = (png_byte)(i >> 16);
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buf[2] = (png_byte)(i >> 8);
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buf[3] = (png_byte)(i );
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/* Place a 16-bit number into a buffer in PNG byte order.
33
* The parameter is declared unsigned int, not png_uint_16,
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* just to avoid potential problems on pre-ANSI C compilers.
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png_save_uint_16(png_bytep buf, unsigned int i)
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buf[0] = (png_byte)(i >> 8);
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buf[1] = (png_byte)(i );
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/* Simple function to write the signature. If we have already written
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* the magic bytes of the signature, or more likely, the PNG stream is
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* being embedded into another stream and doesn't need its own signature,
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* we should call png_set_sig_bytes() to tell libpng how many of the
48
* bytes have already been written.
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png_write_sig(png_structrp png_ptr)
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png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
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#ifdef PNG_IO_STATE_SUPPORTED
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/* Inform the I/O callback that the signature is being written */
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png_ptr->io_state = PNG_IO_WRITING | PNG_IO_SIGNATURE;
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/* Write the rest of the 8 byte signature */
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png_write_data(png_ptr, &png_signature[png_ptr->sig_bytes],
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(png_size_t)(8 - png_ptr->sig_bytes));
64
if (png_ptr->sig_bytes < 3)
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png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
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/* Write the start of a PNG chunk. The type is the chunk type.
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* The total_length is the sum of the lengths of all the data you will be
70
* passing in png_write_chunk_data().
73
png_write_chunk_header(png_structrp png_ptr, png_uint_32 chunk_name,
78
#if defined(PNG_DEBUG) && (PNG_DEBUG > 0)
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PNG_CSTRING_FROM_CHUNK(buf, chunk_name);
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png_debug2(0, "Writing %s chunk, length = %lu", buf, (unsigned long)length);
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#ifdef PNG_IO_STATE_SUPPORTED
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/* Inform the I/O callback that the chunk header is being written.
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* PNG_IO_CHUNK_HDR requires a single I/O call.
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png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_HDR;
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/* Write the length and the chunk name */
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png_save_uint_32(buf, length);
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png_save_uint_32(buf + 4, chunk_name);
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png_write_data(png_ptr, buf, 8);
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/* Put the chunk name into png_ptr->chunk_name */
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png_ptr->chunk_name = chunk_name;
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/* Reset the crc and run it over the chunk name */
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png_reset_crc(png_ptr);
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png_calculate_crc(png_ptr, buf + 4, 4);
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#ifdef PNG_IO_STATE_SUPPORTED
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/* Inform the I/O callback that chunk data will (possibly) be written.
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* PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
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png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_DATA;
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png_write_chunk_start(png_structrp png_ptr, png_const_bytep chunk_string,
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png_write_chunk_header(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), length);
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/* Write the data of a PNG chunk started with png_write_chunk_header().
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* Note that multiple calls to this function are allowed, and that the
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* sum of the lengths from these calls *must* add up to the total_length
124
* given to png_write_chunk_header().
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png_write_chunk_data(png_structrp png_ptr, png_const_bytep data,
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/* Write the data, and run the CRC over it */
134
if (data != NULL && length > 0)
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png_write_data(png_ptr, data, length);
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/* Update the CRC after writing the data,
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* in case the user I/O routine alters it.
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png_calculate_crc(png_ptr, data, length);
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/* Finish a chunk started with png_write_chunk_header(). */
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png_write_chunk_end(png_structrp png_ptr)
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if (png_ptr == NULL) return;
153
#ifdef PNG_IO_STATE_SUPPORTED
154
/* Inform the I/O callback that the chunk CRC is being written.
155
* PNG_IO_CHUNK_CRC requires a single I/O function call.
157
png_ptr->io_state = PNG_IO_WRITING | PNG_IO_CHUNK_CRC;
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/* Write the crc in a single operation */
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png_save_uint_32(buf, png_ptr->crc);
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png_write_data(png_ptr, buf, (png_size_t)4);
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/* Write a PNG chunk all at once. The type is an array of ASCII characters
167
* representing the chunk name. The array must be at least 4 bytes in
168
* length, and does not need to be null terminated. To be safe, pass the
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* pre-defined chunk names here, and if you need a new one, define it
170
* where the others are defined. The length is the length of the data.
171
* All the data must be present. If that is not possible, use the
172
* png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
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png_write_complete_chunk(png_structrp png_ptr, png_uint_32 chunk_name,
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png_const_bytep data, png_size_t length)
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/* On 64-bit architectures 'length' may not fit in a png_uint_32. */
183
if (length > PNG_UINT_31_MAX)
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png_error(png_ptr, "length exceeds PNG maximum");
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png_write_chunk_header(png_ptr, chunk_name, (png_uint_32)length);
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png_write_chunk_data(png_ptr, data, length);
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png_write_chunk_end(png_ptr);
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/* This is the API that calls the internal function above. */
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png_write_chunk(png_structrp png_ptr, png_const_bytep chunk_string,
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png_const_bytep data, png_size_t length)
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png_write_complete_chunk(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), data,
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/* This is used below to find the size of an image to pass to png_deflate_claim,
201
* so it only needs to be accurate if the size is less than 16384 bytes (the
202
* point at which a lower LZ window size can be used.)
204
static png_alloc_size_t
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png_image_size(png_structrp png_ptr)
207
/* Only return sizes up to the maximum of a png_uint_32; do this by limiting
208
* the width and height used to 15 bits.
210
png_uint_32 h = png_ptr->height;
212
if (png_ptr->rowbytes < 32768 && h < 32768)
214
if (png_ptr->interlaced != 0)
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/* Interlacing makes the image larger because of the replication of
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* both the filter byte and the padding to a byte boundary.
219
png_uint_32 w = png_ptr->width;
220
unsigned int pd = png_ptr->pixel_depth;
221
png_alloc_size_t cb_base;
224
for (cb_base=0, pass=0; pass<=6; ++pass)
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png_uint_32 pw = PNG_PASS_COLS(w, pass);
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cb_base += (PNG_ROWBYTES(pd, pw)+1) * PNG_PASS_ROWS(h, pass);
236
return (png_ptr->rowbytes+1) * h;
243
#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
244
/* This is the code to hack the first two bytes of the deflate stream (the
245
* deflate header) to correct the windowBits value to match the actual data
246
* size. Note that the second argument is the *uncompressed* size but the
247
* first argument is the *compressed* data (and it must be deflate
251
optimize_cmf(png_bytep data, png_alloc_size_t data_size)
253
/* Optimize the CMF field in the zlib stream. The resultant zlib stream is
254
* still compliant to the stream specification.
256
if (data_size <= 16384) /* else windowBits must be 15 */
258
unsigned int z_cmf = data[0]; /* zlib compression method and flags */
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if ((z_cmf & 0x0f) == 8 && (z_cmf & 0xf0) <= 0x70)
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unsigned int z_cinfo;
263
unsigned int half_z_window_size;
265
z_cinfo = z_cmf >> 4;
266
half_z_window_size = 1U << (z_cinfo + 7);
268
if (data_size <= half_z_window_size) /* else no change */
274
half_z_window_size >>= 1;
277
while (z_cinfo > 0 && data_size <= half_z_window_size);
279
z_cmf = (z_cmf & 0x0f) | (z_cinfo << 4);
281
data[0] = (png_byte)z_cmf;
282
tmp = data[1] & 0xe0;
283
tmp += 0x1f - ((z_cmf << 8) + tmp) % 0x1f;
284
data[1] = (png_byte)tmp;
289
#endif /* WRITE_OPTIMIZE_CMF */
291
/* Initialize the compressor for the appropriate type of compression. */
293
png_deflate_claim(png_structrp png_ptr, png_uint_32 owner,
294
png_alloc_size_t data_size)
296
if (png_ptr->zowner != 0)
298
#if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_ERROR_TEXT_SUPPORTED)
301
PNG_STRING_FROM_CHUNK(msg, owner);
304
PNG_STRING_FROM_CHUNK(msg+6, png_ptr->zowner);
305
/* So the message that results is "<chunk> using zstream"; this is an
306
* internal error, but is very useful for debugging. i18n requirements
309
(void)png_safecat(msg, (sizeof msg), 10, " using zstream");
311
#if PNG_RELEASE_BUILD
312
png_warning(png_ptr, msg);
314
/* Attempt sane error recovery */
315
if (png_ptr->zowner == png_IDAT) /* don't steal from IDAT */
317
png_ptr->zstream.msg = PNGZ_MSG_CAST("in use by IDAT");
318
return Z_STREAM_ERROR;
323
png_error(png_ptr, msg);
328
int level = png_ptr->zlib_level;
329
int method = png_ptr->zlib_method;
330
int windowBits = png_ptr->zlib_window_bits;
331
int memLevel = png_ptr->zlib_mem_level;
332
int strategy; /* set below */
333
int ret; /* zlib return code */
335
if (owner == png_IDAT)
337
if ((png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_STRATEGY) != 0)
338
strategy = png_ptr->zlib_strategy;
340
else if (png_ptr->do_filter != PNG_FILTER_NONE)
341
strategy = PNG_Z_DEFAULT_STRATEGY;
344
strategy = PNG_Z_DEFAULT_NOFILTER_STRATEGY;
349
#ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
350
level = png_ptr->zlib_text_level;
351
method = png_ptr->zlib_text_method;
352
windowBits = png_ptr->zlib_text_window_bits;
353
memLevel = png_ptr->zlib_text_mem_level;
354
strategy = png_ptr->zlib_text_strategy;
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/* If customization is not supported the values all come from the
357
* IDAT values except for the strategy, which is fixed to the
358
* default. (This is the pre-1.6.0 behavior too, although it was
359
* implemented in a very different way.)
361
strategy = Z_DEFAULT_STRATEGY;
365
/* Adjust 'windowBits' down if larger than 'data_size'; to stop this
366
* happening just pass 32768 as the data_size parameter. Notice that zlib
367
* requires an extra 262 bytes in the window in addition to the data to be
368
* able to see the whole of the data, so if data_size+262 takes us to the
369
* next windowBits size we need to fix up the value later. (Because even
370
* though deflate needs the extra window, inflate does not!)
372
if (data_size <= 16384)
374
/* IMPLEMENTATION NOTE: this 'half_window_size' stuff is only here to
375
* work round a Microsoft Visual C misbehavior which, contrary to C-90,
376
* widens the result of the following shift to 64-bits if (and,
377
* apparently, only if) it is used in a test.
379
unsigned int half_window_size = 1U << (windowBits-1);
381
while (data_size + 262 <= half_window_size)
383
half_window_size >>= 1;
388
/* Check against the previous initialized values, if any. */
389
if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0 &&
390
(png_ptr->zlib_set_level != level ||
391
png_ptr->zlib_set_method != method ||
392
png_ptr->zlib_set_window_bits != windowBits ||
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png_ptr->zlib_set_mem_level != memLevel ||
394
png_ptr->zlib_set_strategy != strategy))
396
if (deflateEnd(&png_ptr->zstream) != Z_OK)
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png_warning(png_ptr, "deflateEnd failed (ignored)");
399
png_ptr->flags &= ~PNG_FLAG_ZSTREAM_INITIALIZED;
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/* For safety clear out the input and output pointers (currently zlib
403
* doesn't use them on Init, but it might in the future).
405
png_ptr->zstream.next_in = NULL;
406
png_ptr->zstream.avail_in = 0;
407
png_ptr->zstream.next_out = NULL;
408
png_ptr->zstream.avail_out = 0;
410
/* Now initialize if required, setting the new parameters, otherwise just
411
* to a simple reset to the previous parameters.
413
if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
414
ret = deflateReset(&png_ptr->zstream);
418
ret = deflateInit2(&png_ptr->zstream, level, method, windowBits,
422
png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
425
/* The return code is from either deflateReset or deflateInit2; they have
426
* pretty much the same set of error codes.
429
png_ptr->zowner = owner;
432
png_zstream_error(png_ptr, ret);
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/* Clean up (or trim) a linked list of compression buffers. */
440
png_free_buffer_list(png_structrp png_ptr, png_compression_bufferp *listp)
442
png_compression_bufferp list = *listp;
450
png_compression_bufferp next = list->next;
452
png_free(png_ptr, list);
455
while (list != NULL);
459
#ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
460
/* This pair of functions encapsulates the operation of (a) compressing a
461
* text string, and (b) issuing it later as a series of chunk data writes.
462
* The compression_state structure is shared context for these functions
463
* set up by the caller to allow access to the relevant local variables.
465
* compression_buffer (new in 1.6.0) is just a linked list of zbuffer_size
466
* temporary buffers. From 1.6.0 it is retained in png_struct so that it will
467
* be correctly freed in the event of a write error (previous implementations
468
* just leaked memory.)
472
png_const_bytep input; /* The uncompressed input data */
473
png_alloc_size_t input_len; /* Its length */
474
png_uint_32 output_len; /* Final compressed length */
475
png_byte output[1024]; /* First block of output */
479
png_text_compress_init(compression_state *comp, png_const_bytep input,
480
png_alloc_size_t input_len)
483
comp->input_len = input_len;
484
comp->output_len = 0;
487
/* Compress the data in the compression state input */
489
png_text_compress(png_structrp png_ptr, png_uint_32 chunk_name,
490
compression_state *comp, png_uint_32 prefix_len)
494
/* To find the length of the output it is necessary to first compress the
495
* input. The result is buffered rather than using the two-pass algorithm
496
* that is used on the inflate side; deflate is assumed to be slower and a
497
* PNG writer is assumed to have more memory available than a PNG reader.
499
* IMPLEMENTATION NOTE: the zlib API deflateBound() can be used to find an
500
* upper limit on the output size, but it is always bigger than the input
501
* size so it is likely to be more efficient to use this linked-list
504
ret = png_deflate_claim(png_ptr, chunk_name, comp->input_len);
509
/* Set up the compression buffers, we need a loop here to avoid overflowing a
510
* uInt. Use ZLIB_IO_MAX to limit the input. The output is always limited
511
* by the output buffer size, so there is no need to check that. Since this
512
* is ANSI-C we know that an 'int', hence a uInt, is always at least 16 bits
516
png_compression_bufferp *end = &png_ptr->zbuffer_list;
517
png_alloc_size_t input_len = comp->input_len; /* may be zero! */
518
png_uint_32 output_len;
520
/* zlib updates these for us: */
521
png_ptr->zstream.next_in = PNGZ_INPUT_CAST(comp->input);
522
png_ptr->zstream.avail_in = 0; /* Set below */
523
png_ptr->zstream.next_out = comp->output;
524
png_ptr->zstream.avail_out = (sizeof comp->output);
526
output_len = png_ptr->zstream.avail_out;
530
uInt avail_in = ZLIB_IO_MAX;
532
if (avail_in > input_len)
533
avail_in = (uInt)input_len;
535
input_len -= avail_in;
537
png_ptr->zstream.avail_in = avail_in;
539
if (png_ptr->zstream.avail_out == 0)
541
png_compression_buffer *next;
543
/* Chunk data is limited to 2^31 bytes in length, so the prefix
544
* length must be counted here.
546
if (output_len + prefix_len > PNG_UINT_31_MAX)
552
/* Need a new (malloc'ed) buffer, but there may be one present
558
next = png_voidcast(png_compression_bufferp, png_malloc_base
559
(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
567
/* Link in this buffer (so that it will be freed later) */
572
png_ptr->zstream.next_out = next->output;
573
png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
574
output_len += png_ptr->zstream.avail_out;
576
/* Move 'end' to the next buffer pointer. */
580
/* Compress the data */
581
ret = deflate(&png_ptr->zstream,
582
input_len > 0 ? Z_NO_FLUSH : Z_FINISH);
584
/* Claw back input data that was not consumed (because avail_in is
585
* reset above every time round the loop).
587
input_len += png_ptr->zstream.avail_in;
588
png_ptr->zstream.avail_in = 0; /* safety */
592
/* There may be some space left in the last output buffer. This needs to
593
* be subtracted from output_len.
595
output_len -= png_ptr->zstream.avail_out;
596
png_ptr->zstream.avail_out = 0; /* safety */
597
comp->output_len = output_len;
599
/* Now double check the output length, put in a custom message if it is
600
* too long. Otherwise ensure the z_stream::msg pointer is set to
603
if (output_len + prefix_len >= PNG_UINT_31_MAX)
605
png_ptr->zstream.msg = PNGZ_MSG_CAST("compressed data too long");
610
png_zstream_error(png_ptr, ret);
612
/* Reset zlib for another zTXt/iTXt or image data */
615
/* The only success case is Z_STREAM_END, input_len must be 0; if not this
616
* is an internal error.
618
if (ret == Z_STREAM_END && input_len == 0)
620
#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
621
/* Fix up the deflate header, if required */
622
optimize_cmf(comp->output, comp->input_len);
624
/* But Z_OK is returned, not Z_STREAM_END; this allows the claim
625
* function above to return Z_STREAM_END on an error (though it never
626
* does in the current versions of zlib.)
636
/* Ship the compressed text out via chunk writes */
638
png_write_compressed_data_out(png_structrp png_ptr, compression_state *comp)
640
png_uint_32 output_len = comp->output_len;
641
png_const_bytep output = comp->output;
642
png_uint_32 avail = (sizeof comp->output);
643
png_compression_buffer *next = png_ptr->zbuffer_list;
647
if (avail > output_len)
650
png_write_chunk_data(png_ptr, output, avail);
654
if (output_len == 0 || next == NULL)
657
avail = png_ptr->zbuffer_size;
658
output = next->output;
662
/* This is an internal error; 'next' must have been NULL! */
664
png_error(png_ptr, "error writing ancillary chunked compressed data");
666
#endif /* WRITE_COMPRESSED_TEXT */
668
/* Write the IHDR chunk, and update the png_struct with the necessary
669
* information. Note that the rest of this code depends upon this
670
* information being correct.
673
png_write_IHDR(png_structrp png_ptr, png_uint_32 width, png_uint_32 height,
674
int bit_depth, int color_type, int compression_type, int filter_type,
677
png_byte buf[13]; /* Buffer to store the IHDR info */
679
png_debug(1, "in png_write_IHDR");
681
/* Check that we have valid input data from the application info */
684
case PNG_COLOR_TYPE_GRAY:
691
#ifdef PNG_WRITE_16BIT_SUPPORTED
694
png_ptr->channels = 1; break;
698
"Invalid bit depth for grayscale image");
702
case PNG_COLOR_TYPE_RGB:
703
#ifdef PNG_WRITE_16BIT_SUPPORTED
704
if (bit_depth != 8 && bit_depth != 16)
708
png_error(png_ptr, "Invalid bit depth for RGB image");
710
png_ptr->channels = 3;
713
case PNG_COLOR_TYPE_PALETTE:
720
png_ptr->channels = 1;
724
png_error(png_ptr, "Invalid bit depth for paletted image");
728
case PNG_COLOR_TYPE_GRAY_ALPHA:
729
if (bit_depth != 8 && bit_depth != 16)
730
png_error(png_ptr, "Invalid bit depth for grayscale+alpha image");
732
png_ptr->channels = 2;
735
case PNG_COLOR_TYPE_RGB_ALPHA:
736
#ifdef PNG_WRITE_16BIT_SUPPORTED
737
if (bit_depth != 8 && bit_depth != 16)
741
png_error(png_ptr, "Invalid bit depth for RGBA image");
743
png_ptr->channels = 4;
747
png_error(png_ptr, "Invalid image color type specified");
750
if (compression_type != PNG_COMPRESSION_TYPE_BASE)
752
png_warning(png_ptr, "Invalid compression type specified");
753
compression_type = PNG_COMPRESSION_TYPE_BASE;
756
/* Write filter_method 64 (intrapixel differencing) only if
757
* 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
758
* 2. Libpng did not write a PNG signature (this filter_method is only
759
* used in PNG datastreams that are embedded in MNG datastreams) and
760
* 3. The application called png_permit_mng_features with a mask that
761
* included PNG_FLAG_MNG_FILTER_64 and
762
* 4. The filter_method is 64 and
763
* 5. The color_type is RGB or RGBA
766
#ifdef PNG_MNG_FEATURES_SUPPORTED
767
!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
768
((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&
769
(color_type == PNG_COLOR_TYPE_RGB ||
770
color_type == PNG_COLOR_TYPE_RGB_ALPHA) &&
771
(filter_type == PNG_INTRAPIXEL_DIFFERENCING)) &&
773
filter_type != PNG_FILTER_TYPE_BASE)
775
png_warning(png_ptr, "Invalid filter type specified");
776
filter_type = PNG_FILTER_TYPE_BASE;
779
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
780
if (interlace_type != PNG_INTERLACE_NONE &&
781
interlace_type != PNG_INTERLACE_ADAM7)
783
png_warning(png_ptr, "Invalid interlace type specified");
784
interlace_type = PNG_INTERLACE_ADAM7;
787
interlace_type=PNG_INTERLACE_NONE;
790
/* Save the relevant information */
791
png_ptr->bit_depth = (png_byte)bit_depth;
792
png_ptr->color_type = (png_byte)color_type;
793
png_ptr->interlaced = (png_byte)interlace_type;
794
#ifdef PNG_MNG_FEATURES_SUPPORTED
795
png_ptr->filter_type = (png_byte)filter_type;
797
png_ptr->compression_type = (png_byte)compression_type;
798
png_ptr->width = width;
799
png_ptr->height = height;
801
png_ptr->pixel_depth = (png_byte)(bit_depth * png_ptr->channels);
802
png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
803
/* Set the usr info, so any transformations can modify it */
804
png_ptr->usr_width = png_ptr->width;
805
png_ptr->usr_bit_depth = png_ptr->bit_depth;
806
png_ptr->usr_channels = png_ptr->channels;
808
/* Pack the header information into the buffer */
809
png_save_uint_32(buf, width);
810
png_save_uint_32(buf + 4, height);
811
buf[8] = (png_byte)bit_depth;
812
buf[9] = (png_byte)color_type;
813
buf[10] = (png_byte)compression_type;
814
buf[11] = (png_byte)filter_type;
815
buf[12] = (png_byte)interlace_type;
817
/* Write the chunk */
818
png_write_complete_chunk(png_ptr, png_IHDR, buf, (png_size_t)13);
820
if ((png_ptr->do_filter) == PNG_NO_FILTERS)
822
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
823
png_ptr->bit_depth < 8)
824
png_ptr->do_filter = PNG_FILTER_NONE;
827
png_ptr->do_filter = PNG_ALL_FILTERS;
830
png_ptr->mode = PNG_HAVE_IHDR; /* not READY_FOR_ZTXT */
833
/* Write the palette. We are careful not to trust png_color to be in the
834
* correct order for PNG, so people can redefine it to any convenient
838
png_write_PLTE(png_structrp png_ptr, png_const_colorp palette,
841
png_uint_32 max_palette_length, i;
842
png_const_colorp pal_ptr;
845
png_debug(1, "in png_write_PLTE");
847
max_palette_length = (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ?
848
(1 << png_ptr->bit_depth) : PNG_MAX_PALETTE_LENGTH;
851
#ifdef PNG_MNG_FEATURES_SUPPORTED
852
(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) == 0 &&
854
num_pal == 0) || num_pal > max_palette_length)
856
if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
858
png_error(png_ptr, "Invalid number of colors in palette");
863
png_warning(png_ptr, "Invalid number of colors in palette");
868
if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) == 0)
871
"Ignoring request to write a PLTE chunk in grayscale PNG");
876
png_ptr->num_palette = (png_uint_16)num_pal;
877
png_debug1(3, "num_palette = %d", png_ptr->num_palette);
879
png_write_chunk_header(png_ptr, png_PLTE, (png_uint_32)(num_pal * 3));
880
#ifdef PNG_POINTER_INDEXING_SUPPORTED
882
for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
884
buf[0] = pal_ptr->red;
885
buf[1] = pal_ptr->green;
886
buf[2] = pal_ptr->blue;
887
png_write_chunk_data(png_ptr, buf, (png_size_t)3);
891
/* This is a little slower but some buggy compilers need to do this
896
for (i = 0; i < num_pal; i++)
898
buf[0] = pal_ptr[i].red;
899
buf[1] = pal_ptr[i].green;
900
buf[2] = pal_ptr[i].blue;
901
png_write_chunk_data(png_ptr, buf, (png_size_t)3);
905
png_write_chunk_end(png_ptr);
906
png_ptr->mode |= PNG_HAVE_PLTE;
909
/* This is similar to png_text_compress, above, except that it does not require
910
* all of the data at once and, instead of buffering the compressed result,
911
* writes it as IDAT chunks. Unlike png_text_compress it *can* png_error out
912
* because it calls the write interface. As a result it does its own error
913
* reporting and does not return an error code. In the event of error it will
914
* just call png_error. The input data length may exceed 32-bits. The 'flush'
915
* parameter is exactly the same as that to deflate, with the following
918
* Z_NO_FLUSH: normal incremental output of compressed data
919
* Z_SYNC_FLUSH: do a SYNC_FLUSH, used by png_write_flush
920
* Z_FINISH: this is the end of the input, do a Z_FINISH and clean up
922
* The routine manages the acquire and release of the png_ptr->zstream by
923
* checking and (at the end) clearing png_ptr->zowner; it does some sanity
924
* checks on the 'mode' flags while doing this.
927
png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
928
png_alloc_size_t input_len, int flush)
930
if (png_ptr->zowner != png_IDAT)
932
/* First time. Ensure we have a temporary buffer for compression and
933
* trim the buffer list if it has more than one entry to free memory.
934
* If 'WRITE_COMPRESSED_TEXT' is not set the list will never have been
935
* created at this point, but the check here is quick and safe.
937
if (png_ptr->zbuffer_list == NULL)
939
png_ptr->zbuffer_list = png_voidcast(png_compression_bufferp,
940
png_malloc(png_ptr, PNG_COMPRESSION_BUFFER_SIZE(png_ptr)));
941
png_ptr->zbuffer_list->next = NULL;
945
png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list->next);
947
/* It is a terminal error if we can't claim the zstream. */
948
if (png_deflate_claim(png_ptr, png_IDAT, png_image_size(png_ptr)) != Z_OK)
949
png_error(png_ptr, png_ptr->zstream.msg);
951
/* The output state is maintained in png_ptr->zstream, so it must be
952
* initialized here after the claim.
954
png_ptr->zstream.next_out = png_ptr->zbuffer_list->output;
955
png_ptr->zstream.avail_out = png_ptr->zbuffer_size;
958
/* Now loop reading and writing until all the input is consumed or an error
959
* terminates the operation. The _out values are maintained across calls to
960
* this function, but the input must be reset each time.
962
png_ptr->zstream.next_in = PNGZ_INPUT_CAST(input);
963
png_ptr->zstream.avail_in = 0; /* set below */
968
/* INPUT: from the row data */
969
uInt avail = ZLIB_IO_MAX;
971
if (avail > input_len)
972
avail = (uInt)input_len; /* safe because of the check */
974
png_ptr->zstream.avail_in = avail;
977
ret = deflate(&png_ptr->zstream, input_len > 0 ? Z_NO_FLUSH : flush);
979
/* Include as-yet unconsumed input */
980
input_len += png_ptr->zstream.avail_in;
981
png_ptr->zstream.avail_in = 0;
983
/* OUTPUT: write complete IDAT chunks when avail_out drops to zero. Note
984
* that these two zstream fields are preserved across the calls, therefore
985
* there is no need to set these up on entry to the loop.
987
if (png_ptr->zstream.avail_out == 0)
989
png_bytep data = png_ptr->zbuffer_list->output;
990
uInt size = png_ptr->zbuffer_size;
992
/* Write an IDAT containing the data then reset the buffer. The
993
* first IDAT may need deflate header optimization.
995
#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
996
if ((png_ptr->mode & PNG_HAVE_IDAT) == 0 &&
997
png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
998
optimize_cmf(data, png_image_size(png_ptr));
1001
png_write_complete_chunk(png_ptr, png_IDAT, data, size);
1002
png_ptr->mode |= PNG_HAVE_IDAT;
1004
png_ptr->zstream.next_out = data;
1005
png_ptr->zstream.avail_out = size;
1007
/* For SYNC_FLUSH or FINISH it is essential to keep calling zlib with
1008
* the same flush parameter until it has finished output, for NO_FLUSH
1009
* it doesn't matter.
1011
if (ret == Z_OK && flush != Z_NO_FLUSH)
1015
/* The order of these checks doesn't matter much; it just affects which
1016
* possible error might be detected if multiple things go wrong at once.
1018
if (ret == Z_OK) /* most likely return code! */
1020
/* If all the input has been consumed then just return. If Z_FINISH
1021
* was used as the flush parameter something has gone wrong if we get
1026
if (flush == Z_FINISH)
1027
png_error(png_ptr, "Z_OK on Z_FINISH with output space");
1033
else if (ret == Z_STREAM_END && flush == Z_FINISH)
1035
/* This is the end of the IDAT data; any pending output must be
1036
* flushed. For small PNG files we may still be at the beginning.
1038
png_bytep data = png_ptr->zbuffer_list->output;
1039
uInt size = png_ptr->zbuffer_size - png_ptr->zstream.avail_out;
1041
#ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
1042
if ((png_ptr->mode & PNG_HAVE_IDAT) == 0 &&
1043
png_ptr->compression_type == PNG_COMPRESSION_TYPE_BASE)
1044
optimize_cmf(data, png_image_size(png_ptr));
1047
png_write_complete_chunk(png_ptr, png_IDAT, data, size);
1048
png_ptr->zstream.avail_out = 0;
1049
png_ptr->zstream.next_out = NULL;
1050
png_ptr->mode |= PNG_HAVE_IDAT | PNG_AFTER_IDAT;
1052
png_ptr->zowner = 0; /* Release the stream */
1058
/* This is an error condition. */
1059
png_zstream_error(png_ptr, ret);
1060
png_error(png_ptr, png_ptr->zstream.msg);
1065
/* Write an IEND chunk */
1067
png_write_IEND(png_structrp png_ptr)
1069
png_debug(1, "in png_write_IEND");
1071
png_write_complete_chunk(png_ptr, png_IEND, NULL, (png_size_t)0);
1072
png_ptr->mode |= PNG_HAVE_IEND;
1075
#ifdef PNG_WRITE_gAMA_SUPPORTED
1076
/* Write a gAMA chunk */
1078
png_write_gAMA_fixed(png_structrp png_ptr, png_fixed_point file_gamma)
1082
png_debug(1, "in png_write_gAMA");
1084
/* file_gamma is saved in 1/100,000ths */
1085
png_save_uint_32(buf, (png_uint_32)file_gamma);
1086
png_write_complete_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
1090
#ifdef PNG_WRITE_sRGB_SUPPORTED
1091
/* Write a sRGB chunk */
1093
png_write_sRGB(png_structrp png_ptr, int srgb_intent)
1097
png_debug(1, "in png_write_sRGB");
1099
if (srgb_intent >= PNG_sRGB_INTENT_LAST)
1100
png_warning(png_ptr,
1101
"Invalid sRGB rendering intent specified");
1103
buf[0]=(png_byte)srgb_intent;
1104
png_write_complete_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
1108
#ifdef PNG_WRITE_iCCP_SUPPORTED
1109
/* Write an iCCP chunk */
1111
png_write_iCCP(png_structrp png_ptr, png_const_charp name,
1112
png_const_bytep profile)
1114
png_uint_32 name_len;
1115
png_uint_32 profile_len;
1116
png_byte new_name[81]; /* 1 byte for the compression byte */
1117
compression_state comp;
1120
png_debug(1, "in png_write_iCCP");
1122
/* These are all internal problems: the profile should have been checked
1123
* before when it was stored.
1125
if (profile == NULL)
1126
png_error(png_ptr, "No profile for iCCP chunk"); /* internal error */
1128
profile_len = png_get_uint_32(profile);
1130
if (profile_len < 132)
1131
png_error(png_ptr, "ICC profile too short");
1133
temp = (png_uint_32) (*(profile+8));
1134
if (temp > 3 && (profile_len & 0x03))
1135
png_error(png_ptr, "ICC profile length invalid (not a multiple of 4)");
1138
png_uint_32 embedded_profile_len = png_get_uint_32(profile);
1140
if (profile_len != embedded_profile_len)
1141
png_error(png_ptr, "Profile length does not match profile");
1144
name_len = png_check_keyword(png_ptr, name, new_name);
1147
png_error(png_ptr, "iCCP: invalid keyword");
1149
new_name[++name_len] = PNG_COMPRESSION_TYPE_BASE;
1151
/* Make sure we include the NULL after the name and the compression type */
1154
png_text_compress_init(&comp, profile, profile_len);
1156
/* Allow for keyword terminator and compression byte */
1157
if (png_text_compress(png_ptr, png_iCCP, &comp, name_len) != Z_OK)
1158
png_error(png_ptr, png_ptr->zstream.msg);
1160
png_write_chunk_header(png_ptr, png_iCCP, name_len + comp.output_len);
1162
png_write_chunk_data(png_ptr, new_name, name_len);
1164
png_write_compressed_data_out(png_ptr, &comp);
1166
png_write_chunk_end(png_ptr);
1170
#ifdef PNG_WRITE_sPLT_SUPPORTED
1171
/* Write a sPLT chunk */
1173
png_write_sPLT(png_structrp png_ptr, png_const_sPLT_tp spalette)
1175
png_uint_32 name_len;
1176
png_byte new_name[80];
1177
png_byte entrybuf[10];
1178
png_size_t entry_size = (spalette->depth == 8 ? 6 : 10);
1179
png_size_t palette_size = entry_size * spalette->nentries;
1181
#ifndef PNG_POINTER_INDEXING_SUPPORTED
1185
png_debug(1, "in png_write_sPLT");
1187
name_len = png_check_keyword(png_ptr, spalette->name, new_name);
1190
png_error(png_ptr, "sPLT: invalid keyword");
1192
/* Make sure we include the NULL after the name */
1193
png_write_chunk_header(png_ptr, png_sPLT,
1194
(png_uint_32)(name_len + 2 + palette_size));
1196
png_write_chunk_data(png_ptr, (png_bytep)new_name,
1197
(png_size_t)(name_len + 1));
1199
png_write_chunk_data(png_ptr, &spalette->depth, (png_size_t)1);
1201
/* Loop through each palette entry, writing appropriately */
1202
#ifdef PNG_POINTER_INDEXING_SUPPORTED
1203
for (ep = spalette->entries; ep<spalette->entries + spalette->nentries; ep++)
1205
if (spalette->depth == 8)
1207
entrybuf[0] = (png_byte)ep->red;
1208
entrybuf[1] = (png_byte)ep->green;
1209
entrybuf[2] = (png_byte)ep->blue;
1210
entrybuf[3] = (png_byte)ep->alpha;
1211
png_save_uint_16(entrybuf + 4, ep->frequency);
1216
png_save_uint_16(entrybuf + 0, ep->red);
1217
png_save_uint_16(entrybuf + 2, ep->green);
1218
png_save_uint_16(entrybuf + 4, ep->blue);
1219
png_save_uint_16(entrybuf + 6, ep->alpha);
1220
png_save_uint_16(entrybuf + 8, ep->frequency);
1223
png_write_chunk_data(png_ptr, entrybuf, entry_size);
1226
ep=spalette->entries;
1227
for (i = 0; i>spalette->nentries; i++)
1229
if (spalette->depth == 8)
1231
entrybuf[0] = (png_byte)ep[i].red;
1232
entrybuf[1] = (png_byte)ep[i].green;
1233
entrybuf[2] = (png_byte)ep[i].blue;
1234
entrybuf[3] = (png_byte)ep[i].alpha;
1235
png_save_uint_16(entrybuf + 4, ep[i].frequency);
1240
png_save_uint_16(entrybuf + 0, ep[i].red);
1241
png_save_uint_16(entrybuf + 2, ep[i].green);
1242
png_save_uint_16(entrybuf + 4, ep[i].blue);
1243
png_save_uint_16(entrybuf + 6, ep[i].alpha);
1244
png_save_uint_16(entrybuf + 8, ep[i].frequency);
1247
png_write_chunk_data(png_ptr, entrybuf, entry_size);
1251
png_write_chunk_end(png_ptr);
1255
#ifdef PNG_WRITE_sBIT_SUPPORTED
1256
/* Write the sBIT chunk */
1258
png_write_sBIT(png_structrp png_ptr, png_const_color_8p sbit, int color_type)
1263
png_debug(1, "in png_write_sBIT");
1265
/* Make sure we don't depend upon the order of PNG_COLOR_8 */
1266
if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
1270
maxbits = (png_byte)(color_type==PNG_COLOR_TYPE_PALETTE ? 8 :
1271
png_ptr->usr_bit_depth);
1273
if (sbit->red == 0 || sbit->red > maxbits ||
1274
sbit->green == 0 || sbit->green > maxbits ||
1275
sbit->blue == 0 || sbit->blue > maxbits)
1277
png_warning(png_ptr, "Invalid sBIT depth specified");
1282
buf[1] = sbit->green;
1283
buf[2] = sbit->blue;
1289
if (sbit->gray == 0 || sbit->gray > png_ptr->usr_bit_depth)
1291
png_warning(png_ptr, "Invalid sBIT depth specified");
1295
buf[0] = sbit->gray;
1299
if ((color_type & PNG_COLOR_MASK_ALPHA) != 0)
1301
if (sbit->alpha == 0 || sbit->alpha > png_ptr->usr_bit_depth)
1303
png_warning(png_ptr, "Invalid sBIT depth specified");
1307
buf[size++] = sbit->alpha;
1310
png_write_complete_chunk(png_ptr, png_sBIT, buf, size);
1314
#ifdef PNG_WRITE_cHRM_SUPPORTED
1315
/* Write the cHRM chunk */
1317
png_write_cHRM_fixed(png_structrp png_ptr, const png_xy *xy)
1321
png_debug(1, "in png_write_cHRM");
1323
/* Each value is saved in 1/100,000ths */
1324
png_save_int_32(buf, xy->whitex);
1325
png_save_int_32(buf + 4, xy->whitey);
1327
png_save_int_32(buf + 8, xy->redx);
1328
png_save_int_32(buf + 12, xy->redy);
1330
png_save_int_32(buf + 16, xy->greenx);
1331
png_save_int_32(buf + 20, xy->greeny);
1333
png_save_int_32(buf + 24, xy->bluex);
1334
png_save_int_32(buf + 28, xy->bluey);
1336
png_write_complete_chunk(png_ptr, png_cHRM, buf, 32);
1340
#ifdef PNG_WRITE_tRNS_SUPPORTED
1341
/* Write the tRNS chunk */
1343
png_write_tRNS(png_structrp png_ptr, png_const_bytep trans_alpha,
1344
png_const_color_16p tran, int num_trans, int color_type)
1348
png_debug(1, "in png_write_tRNS");
1350
if (color_type == PNG_COLOR_TYPE_PALETTE)
1352
if (num_trans <= 0 || num_trans > (int)png_ptr->num_palette)
1354
png_app_warning(png_ptr,
1355
"Invalid number of transparent colors specified");
1359
/* Write the chunk out as it is */
1360
png_write_complete_chunk(png_ptr, png_tRNS, trans_alpha,
1361
(png_size_t)num_trans);
1364
else if (color_type == PNG_COLOR_TYPE_GRAY)
1366
/* One 16-bit value */
1367
if (tran->gray >= (1 << png_ptr->bit_depth))
1369
png_app_warning(png_ptr,
1370
"Ignoring attempt to write tRNS chunk out-of-range for bit_depth");
1375
png_save_uint_16(buf, tran->gray);
1376
png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)2);
1379
else if (color_type == PNG_COLOR_TYPE_RGB)
1381
/* Three 16-bit values */
1382
png_save_uint_16(buf, tran->red);
1383
png_save_uint_16(buf + 2, tran->green);
1384
png_save_uint_16(buf + 4, tran->blue);
1385
#ifdef PNG_WRITE_16BIT_SUPPORTED
1386
if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]) != 0)
1388
if ((buf[0] | buf[2] | buf[4]) != 0)
1391
png_app_warning(png_ptr,
1392
"Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
1396
png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)6);
1401
png_app_warning(png_ptr, "Can't write tRNS with an alpha channel");
1406
#ifdef PNG_WRITE_bKGD_SUPPORTED
1407
/* Write the background chunk */
1409
png_write_bKGD(png_structrp png_ptr, png_const_color_16p back, int color_type)
1413
png_debug(1, "in png_write_bKGD");
1415
if (color_type == PNG_COLOR_TYPE_PALETTE)
1418
#ifdef PNG_MNG_FEATURES_SUPPORTED
1419
(png_ptr->num_palette != 0 ||
1420
(png_ptr->mng_features_permitted & PNG_FLAG_MNG_EMPTY_PLTE) == 0) &&
1422
back->index >= png_ptr->num_palette)
1424
png_warning(png_ptr, "Invalid background palette index");
1428
buf[0] = back->index;
1429
png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)1);
1432
else if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
1434
png_save_uint_16(buf, back->red);
1435
png_save_uint_16(buf + 2, back->green);
1436
png_save_uint_16(buf + 4, back->blue);
1437
#ifdef PNG_WRITE_16BIT_SUPPORTED
1438
if (png_ptr->bit_depth == 8 && (buf[0] | buf[2] | buf[4]) != 0)
1440
if ((buf[0] | buf[2] | buf[4]) != 0)
1443
png_warning(png_ptr,
1444
"Ignoring attempt to write 16-bit bKGD chunk when bit_depth is 8");
1449
png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)6);
1454
if (back->gray >= (1 << png_ptr->bit_depth))
1456
png_warning(png_ptr,
1457
"Ignoring attempt to write bKGD chunk out-of-range for bit_depth");
1462
png_save_uint_16(buf, back->gray);
1463
png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)2);
1468
#ifdef PNG_WRITE_hIST_SUPPORTED
1469
/* Write the histogram */
1471
png_write_hIST(png_structrp png_ptr, png_const_uint_16p hist, int num_hist)
1476
png_debug(1, "in png_write_hIST");
1478
if (num_hist > (int)png_ptr->num_palette)
1480
png_debug2(3, "num_hist = %d, num_palette = %d", num_hist,
1481
png_ptr->num_palette);
1483
png_warning(png_ptr, "Invalid number of histogram entries specified");
1487
png_write_chunk_header(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
1489
for (i = 0; i < num_hist; i++)
1491
png_save_uint_16(buf, hist[i]);
1492
png_write_chunk_data(png_ptr, buf, (png_size_t)2);
1495
png_write_chunk_end(png_ptr);
1499
#ifdef PNG_WRITE_tEXt_SUPPORTED
1500
/* Write a tEXt chunk */
1502
png_write_tEXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
1503
png_size_t text_len)
1505
png_uint_32 key_len;
1506
png_byte new_key[80];
1508
png_debug(1, "in png_write_tEXt");
1510
key_len = png_check_keyword(png_ptr, key, new_key);
1513
png_error(png_ptr, "tEXt: invalid keyword");
1515
if (text == NULL || *text == '\0')
1519
text_len = strlen(text);
1521
if (text_len > PNG_UINT_31_MAX - (key_len+1))
1522
png_error(png_ptr, "tEXt: text too long");
1524
/* Make sure we include the 0 after the key */
1525
png_write_chunk_header(png_ptr, png_tEXt,
1526
(png_uint_32)/*checked above*/(key_len + text_len + 1));
1528
* We leave it to the application to meet PNG-1.0 requirements on the
1529
* contents of the text. PNG-1.0 through PNG-1.2 discourage the use of
1530
* any non-Latin-1 characters except for NEWLINE. ISO PNG will forbid them.
1531
* The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
1533
png_write_chunk_data(png_ptr, new_key, key_len + 1);
1536
png_write_chunk_data(png_ptr, (png_const_bytep)text, text_len);
1538
png_write_chunk_end(png_ptr);
1542
#ifdef PNG_WRITE_zTXt_SUPPORTED
1543
/* Write a compressed text chunk */
1545
png_write_zTXt(png_structrp png_ptr, png_const_charp key, png_const_charp text,
1548
png_uint_32 key_len;
1549
png_byte new_key[81];
1550
compression_state comp;
1552
png_debug(1, "in png_write_zTXt");
1554
if (compression == PNG_TEXT_COMPRESSION_NONE)
1556
png_write_tEXt(png_ptr, key, text, 0);
1560
if (compression != PNG_TEXT_COMPRESSION_zTXt)
1561
png_error(png_ptr, "zTXt: invalid compression type");
1563
key_len = png_check_keyword(png_ptr, key, new_key);
1566
png_error(png_ptr, "zTXt: invalid keyword");
1568
/* Add the compression method and 1 for the keyword separator. */
1569
new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
1572
/* Compute the compressed data; do it now for the length */
1573
png_text_compress_init(&comp, (png_const_bytep)text,
1574
text == NULL ? 0 : strlen(text));
1576
if (png_text_compress(png_ptr, png_zTXt, &comp, key_len) != Z_OK)
1577
png_error(png_ptr, png_ptr->zstream.msg);
1579
/* Write start of chunk */
1580
png_write_chunk_header(png_ptr, png_zTXt, key_len + comp.output_len);
1583
png_write_chunk_data(png_ptr, new_key, key_len);
1585
/* Write the compressed data */
1586
png_write_compressed_data_out(png_ptr, &comp);
1588
/* Close the chunk */
1589
png_write_chunk_end(png_ptr);
1593
#ifdef PNG_WRITE_iTXt_SUPPORTED
1594
/* Write an iTXt chunk */
1596
png_write_iTXt(png_structrp png_ptr, int compression, png_const_charp key,
1597
png_const_charp lang, png_const_charp lang_key, png_const_charp text)
1599
png_uint_32 key_len, prefix_len;
1600
png_size_t lang_len, lang_key_len;
1601
png_byte new_key[82];
1602
compression_state comp;
1604
png_debug(1, "in png_write_iTXt");
1606
key_len = png_check_keyword(png_ptr, key, new_key);
1609
png_error(png_ptr, "iTXt: invalid keyword");
1611
/* Set the compression flag */
1612
switch (compression)
1614
case PNG_ITXT_COMPRESSION_NONE:
1615
case PNG_TEXT_COMPRESSION_NONE:
1616
compression = new_key[++key_len] = 0; /* no compression */
1619
case PNG_TEXT_COMPRESSION_zTXt:
1620
case PNG_ITXT_COMPRESSION_zTXt:
1621
compression = new_key[++key_len] = 1; /* compressed */
1625
png_error(png_ptr, "iTXt: invalid compression");
1628
new_key[++key_len] = PNG_COMPRESSION_TYPE_BASE;
1629
++key_len; /* for the keywod separator */
1631
/* We leave it to the application to meet PNG-1.0 requirements on the
1632
* contents of the text. PNG-1.0 through PNG-1.2 discourage the use of
1633
* any non-Latin-1 characters except for NEWLINE. ISO PNG, however,
1634
* specifies that the text is UTF-8 and this really doesn't require any
1637
* The NUL character is forbidden by PNG-1.0 through PNG-1.2 and ISO PNG.
1639
* TODO: validate the language tag correctly (see the spec.)
1641
if (lang == NULL) lang = ""; /* empty language is valid */
1642
lang_len = strlen(lang)+1;
1643
if (lang_key == NULL) lang_key = ""; /* may be empty */
1644
lang_key_len = strlen(lang_key)+1;
1645
if (text == NULL) text = ""; /* may be empty */
1647
prefix_len = key_len;
1648
if (lang_len > PNG_UINT_31_MAX-prefix_len)
1649
prefix_len = PNG_UINT_31_MAX;
1651
prefix_len = (png_uint_32)(prefix_len + lang_len);
1653
if (lang_key_len > PNG_UINT_31_MAX-prefix_len)
1654
prefix_len = PNG_UINT_31_MAX;
1656
prefix_len = (png_uint_32)(prefix_len + lang_key_len);
1658
png_text_compress_init(&comp, (png_const_bytep)text, strlen(text));
1660
if (compression != 0)
1662
if (png_text_compress(png_ptr, png_iTXt, &comp, prefix_len) != Z_OK)
1663
png_error(png_ptr, png_ptr->zstream.msg);
1668
if (comp.input_len > PNG_UINT_31_MAX-prefix_len)
1669
png_error(png_ptr, "iTXt: uncompressed text too long");
1671
/* So the string will fit in a chunk: */
1672
comp.output_len = (png_uint_32)/*SAFE*/comp.input_len;
1675
png_write_chunk_header(png_ptr, png_iTXt, comp.output_len + prefix_len);
1677
png_write_chunk_data(png_ptr, new_key, key_len);
1679
png_write_chunk_data(png_ptr, (png_const_bytep)lang, lang_len);
1681
png_write_chunk_data(png_ptr, (png_const_bytep)lang_key, lang_key_len);
1683
if (compression != 0)
1684
png_write_compressed_data_out(png_ptr, &comp);
1687
png_write_chunk_data(png_ptr, (png_const_bytep)text, comp.output_len);
1689
png_write_chunk_end(png_ptr);
1693
#ifdef PNG_WRITE_oFFs_SUPPORTED
1694
/* Write the oFFs chunk */
1696
png_write_oFFs(png_structrp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
1701
png_debug(1, "in png_write_oFFs");
1703
if (unit_type >= PNG_OFFSET_LAST)
1704
png_warning(png_ptr, "Unrecognized unit type for oFFs chunk");
1706
png_save_int_32(buf, x_offset);
1707
png_save_int_32(buf + 4, y_offset);
1708
buf[8] = (png_byte)unit_type;
1710
png_write_complete_chunk(png_ptr, png_oFFs, buf, (png_size_t)9);
1713
#ifdef PNG_WRITE_pCAL_SUPPORTED
1714
/* Write the pCAL chunk (described in the PNG extensions document) */
1716
png_write_pCAL(png_structrp png_ptr, png_charp purpose, png_int_32 X0,
1717
png_int_32 X1, int type, int nparams, png_const_charp units,
1720
png_uint_32 purpose_len;
1721
png_size_t units_len, total_len;
1722
png_size_tp params_len;
1724
png_byte new_purpose[80];
1727
png_debug1(1, "in png_write_pCAL (%d parameters)", nparams);
1729
if (type >= PNG_EQUATION_LAST)
1730
png_error(png_ptr, "Unrecognized equation type for pCAL chunk");
1732
purpose_len = png_check_keyword(png_ptr, purpose, new_purpose);
1734
if (purpose_len == 0)
1735
png_error(png_ptr, "pCAL: invalid keyword");
1737
++purpose_len; /* terminator */
1739
png_debug1(3, "pCAL purpose length = %d", (int)purpose_len);
1740
units_len = strlen(units) + (nparams == 0 ? 0 : 1);
1741
png_debug1(3, "pCAL units length = %d", (int)units_len);
1742
total_len = purpose_len + units_len + 10;
1744
params_len = (png_size_tp)png_malloc(png_ptr,
1745
(png_alloc_size_t)(nparams * (sizeof (png_size_t))));
1747
/* Find the length of each parameter, making sure we don't count the
1748
* null terminator for the last parameter.
1750
for (i = 0; i < nparams; i++)
1752
params_len[i] = strlen(params[i]) + (i == nparams - 1 ? 0 : 1);
1753
png_debug2(3, "pCAL parameter %d length = %lu", i,
1754
(unsigned long)params_len[i]);
1755
total_len += params_len[i];
1758
png_debug1(3, "pCAL total length = %d", (int)total_len);
1759
png_write_chunk_header(png_ptr, png_pCAL, (png_uint_32)total_len);
1760
png_write_chunk_data(png_ptr, new_purpose, purpose_len);
1761
png_save_int_32(buf, X0);
1762
png_save_int_32(buf + 4, X1);
1763
buf[8] = (png_byte)type;
1764
buf[9] = (png_byte)nparams;
1765
png_write_chunk_data(png_ptr, buf, (png_size_t)10);
1766
png_write_chunk_data(png_ptr, (png_const_bytep)units, (png_size_t)units_len);
1768
for (i = 0; i < nparams; i++)
1770
png_write_chunk_data(png_ptr, (png_const_bytep)params[i], params_len[i]);
1773
png_free(png_ptr, params_len);
1774
png_write_chunk_end(png_ptr);
1778
#ifdef PNG_WRITE_sCAL_SUPPORTED
1779
/* Write the sCAL chunk */
1781
png_write_sCAL_s(png_structrp png_ptr, int unit, png_const_charp width,
1782
png_const_charp height)
1785
png_size_t wlen, hlen, total_len;
1787
png_debug(1, "in png_write_sCAL_s");
1789
wlen = strlen(width);
1790
hlen = strlen(height);
1791
total_len = wlen + hlen + 2;
1795
png_warning(png_ptr, "Can't write sCAL (buffer too small)");
1799
buf[0] = (png_byte)unit;
1800
memcpy(buf + 1, width, wlen + 1); /* Append the '\0' here */
1801
memcpy(buf + wlen + 2, height, hlen); /* Do NOT append the '\0' here */
1803
png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
1804
png_write_complete_chunk(png_ptr, png_sCAL, buf, total_len);
1808
#ifdef PNG_WRITE_pHYs_SUPPORTED
1809
/* Write the pHYs chunk */
1811
png_write_pHYs(png_structrp png_ptr, png_uint_32 x_pixels_per_unit,
1812
png_uint_32 y_pixels_per_unit,
1817
png_debug(1, "in png_write_pHYs");
1819
if (unit_type >= PNG_RESOLUTION_LAST)
1820
png_warning(png_ptr, "Unrecognized unit type for pHYs chunk");
1822
png_save_uint_32(buf, x_pixels_per_unit);
1823
png_save_uint_32(buf + 4, y_pixels_per_unit);
1824
buf[8] = (png_byte)unit_type;
1826
png_write_complete_chunk(png_ptr, png_pHYs, buf, (png_size_t)9);
1830
#ifdef PNG_WRITE_tIME_SUPPORTED
1831
/* Write the tIME chunk. Use either png_convert_from_struct_tm()
1832
* or png_convert_from_time_t(), or fill in the structure yourself.
1835
png_write_tIME(png_structrp png_ptr, png_const_timep mod_time)
1839
png_debug(1, "in png_write_tIME");
1841
if (mod_time->month > 12 || mod_time->month < 1 ||
1842
mod_time->day > 31 || mod_time->day < 1 ||
1843
mod_time->hour > 23 || mod_time->second > 60)
1845
png_warning(png_ptr, "Invalid time specified for tIME chunk");
1849
png_save_uint_16(buf, mod_time->year);
1850
buf[2] = mod_time->month;
1851
buf[3] = mod_time->day;
1852
buf[4] = mod_time->hour;
1853
buf[5] = mod_time->minute;
1854
buf[6] = mod_time->second;
1856
png_write_complete_chunk(png_ptr, png_tIME, buf, (png_size_t)7);
1860
/* Initializes the row writing capability of libpng */
1862
png_write_start_row(png_structrp png_ptr)
1864
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
1865
/* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
1867
/* Start of interlace block */
1868
static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
1870
/* Offset to next interlace block */
1871
static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
1873
/* Start of interlace block in the y direction */
1874
static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
1876
/* Offset to next interlace block in the y direction */
1877
static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
1880
png_alloc_size_t buf_size;
1881
int usr_pixel_depth;
1883
#ifdef PNG_WRITE_FILTER_SUPPORTED
1887
png_debug(1, "in png_write_start_row");
1889
usr_pixel_depth = png_ptr->usr_channels * png_ptr->usr_bit_depth;
1890
buf_size = PNG_ROWBYTES(usr_pixel_depth, png_ptr->width) + 1;
1892
/* 1.5.6: added to allow checking in the row write code. */
1893
png_ptr->transformed_pixel_depth = png_ptr->pixel_depth;
1894
png_ptr->maximum_pixel_depth = (png_byte)usr_pixel_depth;
1896
/* Set up row buffer */
1897
png_ptr->row_buf = png_voidcast(png_bytep, png_malloc(png_ptr, buf_size));
1899
png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
1901
#ifdef PNG_WRITE_FILTER_SUPPORTED
1902
filters = png_ptr->do_filter;
1904
if (png_ptr->height == 1)
1905
filters &= 0xff & ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
1907
if (png_ptr->width == 1)
1908
filters &= 0xff & ~(PNG_FILTER_SUB|PNG_FILTER_AVG|PNG_FILTER_PAETH);
1911
filters = PNG_FILTER_NONE;
1913
png_ptr->do_filter = filters;
1915
if (((filters & (PNG_FILTER_SUB | PNG_FILTER_UP | PNG_FILTER_AVG |
1916
PNG_FILTER_PAETH)) != 0) && png_ptr->try_row == NULL)
1918
int num_filters = 0;
1920
png_ptr->try_row = png_voidcast(png_bytep, png_malloc(png_ptr, buf_size));
1922
if (filters & PNG_FILTER_SUB)
1925
if (filters & PNG_FILTER_UP)
1928
if (filters & PNG_FILTER_AVG)
1931
if (filters & PNG_FILTER_PAETH)
1934
if (num_filters > 1)
1935
png_ptr->tst_row = png_voidcast(png_bytep, png_malloc(png_ptr,
1939
/* We only need to keep the previous row if we are using one of the following
1942
if ((filters & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH)) != 0)
1943
png_ptr->prev_row = png_voidcast(png_bytep,
1944
png_calloc(png_ptr, buf_size));
1945
#endif /* WRITE_FILTER */
1947
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
1948
/* If interlaced, we need to set up width and height of pass */
1949
if (png_ptr->interlaced != 0)
1951
if ((png_ptr->transformations & PNG_INTERLACE) == 0)
1953
png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
1954
png_pass_ystart[0]) / png_pass_yinc[0];
1956
png_ptr->usr_width = (png_ptr->width + png_pass_inc[0] - 1 -
1957
png_pass_start[0]) / png_pass_inc[0];
1962
png_ptr->num_rows = png_ptr->height;
1963
png_ptr->usr_width = png_ptr->width;
1970
png_ptr->num_rows = png_ptr->height;
1971
png_ptr->usr_width = png_ptr->width;
1975
/* Internal use only. Called when finished processing a row of data. */
1977
png_write_finish_row(png_structrp png_ptr)
1979
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
1980
/* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
1982
/* Start of interlace block */
1983
static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
1985
/* Offset to next interlace block */
1986
static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
1988
/* Start of interlace block in the y direction */
1989
static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
1991
/* Offset to next interlace block in the y direction */
1992
static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
1995
png_debug(1, "in png_write_finish_row");
1998
png_ptr->row_number++;
2000
/* See if we are done */
2001
if (png_ptr->row_number < png_ptr->num_rows)
2004
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
2005
/* If interlaced, go to next pass */
2006
if (png_ptr->interlaced != 0)
2008
png_ptr->row_number = 0;
2009
if ((png_ptr->transformations & PNG_INTERLACE) != 0)
2016
/* Loop until we find a non-zero width or height pass */
2021
if (png_ptr->pass >= 7)
2024
png_ptr->usr_width = (png_ptr->width +
2025
png_pass_inc[png_ptr->pass] - 1 -
2026
png_pass_start[png_ptr->pass]) /
2027
png_pass_inc[png_ptr->pass];
2029
png_ptr->num_rows = (png_ptr->height +
2030
png_pass_yinc[png_ptr->pass] - 1 -
2031
png_pass_ystart[png_ptr->pass]) /
2032
png_pass_yinc[png_ptr->pass];
2034
if ((png_ptr->transformations & PNG_INTERLACE) != 0)
2037
} while (png_ptr->usr_width == 0 || png_ptr->num_rows == 0);
2041
/* Reset the row above the image for the next pass */
2042
if (png_ptr->pass < 7)
2044
if (png_ptr->prev_row != NULL)
2045
memset(png_ptr->prev_row, 0,
2046
(png_size_t)(PNG_ROWBYTES(png_ptr->usr_channels*
2047
png_ptr->usr_bit_depth, png_ptr->width)) + 1);
2054
/* If we get here, we've just written the last row, so we need
2055
to flush the compressor */
2056
png_compress_IDAT(png_ptr, NULL, 0, Z_FINISH);
2059
#ifdef PNG_WRITE_INTERLACING_SUPPORTED
2060
/* Pick out the correct pixels for the interlace pass.
2061
* The basic idea here is to go through the row with a source
2062
* pointer and a destination pointer (sp and dp), and copy the
2063
* correct pixels for the pass. As the row gets compacted,
2064
* sp will always be >= dp, so we should never overwrite anything.
2065
* See the default: case for the easiest code to understand.
2068
png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
2070
/* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
2072
/* Start of interlace block */
2073
static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
2075
/* Offset to next interlace block */
2076
static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
2078
png_debug(1, "in png_do_write_interlace");
2080
/* We don't have to do anything on the last pass (6) */
2083
/* Each pixel depth is handled separately */
2084
switch (row_info->pixel_depth)
2094
png_uint_32 row_width = row_info->width;
2100
for (i = png_pass_start[pass]; i < row_width;
2101
i += png_pass_inc[pass])
2103
sp = row + (png_size_t)(i >> 3);
2104
value = (int)(*sp >> (7 - (int)(i & 0x07))) & 0x01;
2105
d |= (value << shift);
2110
*dp++ = (png_byte)d;
2132
png_uint_32 row_width = row_info->width;
2138
for (i = png_pass_start[pass]; i < row_width;
2139
i += png_pass_inc[pass])
2141
sp = row + (png_size_t)(i >> 2);
2142
value = (*sp >> ((3 - (int)(i & 0x03)) << 1)) & 0x03;
2143
d |= (value << shift);
2148
*dp++ = (png_byte)d;
2169
png_uint_32 row_width = row_info->width;
2174
for (i = png_pass_start[pass]; i < row_width;
2175
i += png_pass_inc[pass])
2177
sp = row + (png_size_t)(i >> 1);
2178
value = (*sp >> ((1 - (int)(i & 0x01)) << 2)) & 0x0f;
2179
d |= (value << shift);
2184
*dp++ = (png_byte)d;
2202
png_uint_32 row_width = row_info->width;
2203
png_size_t pixel_bytes;
2205
/* Start at the beginning */
2208
/* Find out how many bytes each pixel takes up */
2209
pixel_bytes = (row_info->pixel_depth >> 3);
2211
/* Loop through the row, only looking at the pixels that matter */
2212
for (i = png_pass_start[pass]; i < row_width;
2213
i += png_pass_inc[pass])
2215
/* Find out where the original pixel is */
2216
sp = row + (png_size_t)i * pixel_bytes;
2218
/* Move the pixel */
2220
memcpy(dp, sp, pixel_bytes);
2228
/* Set new row width */
2229
row_info->width = (row_info->width +
2230
png_pass_inc[pass] - 1 -
2231
png_pass_start[pass]) /
2234
row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
2241
/* This filters the row, chooses which filter to use, if it has not already
2242
* been specified by the application, and then writes the row out with the
2245
static void /* PRIVATE */
2246
png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
2247
png_size_t row_bytes);
2249
#ifdef PNG_WRITE_FILTER_SUPPORTED
2250
static png_size_t /* PRIVATE */
2251
png_setup_sub_row(png_structrp png_ptr, const png_uint_32 bpp,
2252
const png_size_t row_bytes, const png_size_t lmins)
2254
png_bytep rp, dp, lp;
2259
png_ptr->try_row[0] = PNG_FILTER_VALUE_SUB;
2261
for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1; i < bpp;
2265
sum += (v < 128) ? v : 256 - v;
2268
for (lp = png_ptr->row_buf + 1; i < row_bytes;
2269
i++, rp++, lp++, dp++)
2271
v = *dp = (png_byte)(((int)*rp - (int)*lp) & 0xff);
2272
sum += (v < 128) ? v : 256 - v;
2274
if (sum > lmins) /* We are already worse, don't continue. */
2281
static png_size_t /* PRIVATE */
2282
png_setup_up_row(png_structrp png_ptr, const png_size_t row_bytes,
2283
const png_size_t lmins)
2285
png_bytep rp, dp, pp;
2290
png_ptr->try_row[0] = PNG_FILTER_VALUE_UP;
2292
for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2293
pp = png_ptr->prev_row + 1; i < row_bytes;
2294
i++, rp++, pp++, dp++)
2296
v = *dp = (png_byte)(((int)*rp - (int)*pp) & 0xff);
2297
sum += (v < 128) ? v : 256 - v;
2299
if (sum > lmins) /* We are already worse, don't continue. */
2306
static png_size_t /* PRIVATE */
2307
png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
2308
const png_size_t row_bytes, const png_size_t lmins)
2310
png_bytep rp, dp, pp, lp;
2315
png_ptr->try_row[0] = PNG_FILTER_VALUE_AVG;
2317
for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2318
pp = png_ptr->prev_row + 1; i < bpp; i++)
2320
v = *dp++ = (png_byte)(((int)*rp++ - ((int)*pp++ / 2)) & 0xff);
2322
sum += (v < 128) ? v : 256 - v;
2325
for (lp = png_ptr->row_buf + 1; i < row_bytes; i++)
2327
v = *dp++ = (png_byte)(((int)*rp++ - (((int)*pp++ + (int)*lp++) / 2))
2330
sum += (v < 128) ? v : 256 - v;
2332
if (sum > lmins) /* We are already worse, don't continue. */
2339
static png_size_t /* PRIVATE */
2340
png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
2341
const png_size_t row_bytes, const png_size_t lmins)
2343
png_bytep rp, dp, pp, cp, lp;
2348
png_ptr->try_row[0] = PNG_FILTER_VALUE_PAETH;
2350
for (i = 0, rp = png_ptr->row_buf + 1, dp = png_ptr->try_row + 1,
2351
pp = png_ptr->prev_row + 1; i < bpp; i++)
2353
v = *dp++ = (png_byte)(((int)*rp++ - (int)*pp++) & 0xff);
2355
sum += (v < 128) ? v : 256 - v;
2358
for (lp = png_ptr->row_buf + 1, cp = png_ptr->prev_row + 1; i < row_bytes;
2361
int a, b, c, pa, pb, pc, p;
2375
pa = p < 0 ? -p : p;
2376
pb = pc < 0 ? -pc : pc;
2377
pc = (p + pc) < 0 ? -(p + pc) : p + pc;
2380
p = (pa <= pb && pa <=pc) ? a : (pb <= pc) ? b : c;
2382
v = *dp++ = (png_byte)(((int)*rp++ - p) & 0xff);
2384
sum += (v < 128) ? v : 256 - v;
2386
if (sum > lmins) /* We are already worse, don't continue. */
2392
#endif /* WRITE_FILTER */
2395
png_write_find_filter(png_structrp png_ptr, png_row_infop row_info)
2397
#ifndef PNG_WRITE_FILTER_SUPPORTED
2398
png_write_filtered_row(png_ptr, png_ptr->row_buf, row_info->rowbytes+1);
2400
png_byte filter_to_do = png_ptr->do_filter;
2405
png_size_t row_bytes = row_info->rowbytes;
2407
png_debug(1, "in png_write_find_filter");
2409
/* Find out how many bytes offset each pixel is */
2410
bpp = (row_info->pixel_depth + 7) >> 3;
2412
row_buf = png_ptr->row_buf;
2413
mins = PNG_SIZE_MAX - 256/* so we can detect potential overflow of the
2416
/* The prediction method we use is to find which method provides the
2417
* smallest value when summing the absolute values of the distances
2418
* from zero, using anything >= 128 as negative numbers. This is known
2419
* as the "minimum sum of absolute differences" heuristic. Other
2420
* heuristics are the "weighted minimum sum of absolute differences"
2421
* (experimental and can in theory improve compression), and the "zlib
2422
* predictive" method (not implemented yet), which does test compressions
2423
* of lines using different filter methods, and then chooses the
2424
* (series of) filter(s) that give minimum compressed data size (VERY
2425
* computationally expensive).
2427
* GRR 980525: consider also
2429
* (1) minimum sum of absolute differences from running average (i.e.,
2430
* keep running sum of non-absolute differences & count of bytes)
2431
* [track dispersion, too? restart average if dispersion too large?]
2433
* (1b) minimum sum of absolute differences from sliding average, probably
2434
* with window size <= deflate window (usually 32K)
2436
* (2) minimum sum of squared differences from zero or running average
2437
* (i.e., ~ root-mean-square approach)
2441
/* We don't need to test the 'no filter' case if this is the only filter
2442
* that has been chosen, as it doesn't actually do anything to the data.
2444
best_row = png_ptr->row_buf;
2447
if ((filter_to_do & PNG_FILTER_NONE) != 0 && filter_to_do != PNG_FILTER_NONE)
2454
if (PNG_SIZE_MAX/128 <= row_bytes)
2456
for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
2458
/* Check for overflow */
2459
if (sum > PNG_SIZE_MAX/128 - 256)
2463
sum += (v < 128) ? v : 256 - v;
2466
else /* Overflow is not possible */
2468
for (i = 0, rp = row_buf + 1; i < row_bytes; i++, rp++)
2471
sum += (v < 128) ? v : 256 - v;
2479
if (filter_to_do == PNG_FILTER_SUB)
2480
/* It's the only filter so no testing is needed */
2482
(void) png_setup_sub_row(png_ptr, bpp, row_bytes, mins);
2483
best_row = png_ptr->try_row;
2486
else if ((filter_to_do & PNG_FILTER_SUB) != 0)
2489
png_size_t lmins = mins;
2491
sum = png_setup_sub_row(png_ptr, bpp, row_bytes, lmins);
2496
best_row = png_ptr->try_row;
2497
if (png_ptr->tst_row != NULL)
2499
png_ptr->try_row = png_ptr->tst_row;
2500
png_ptr->tst_row = best_row;
2506
if (filter_to_do == PNG_FILTER_UP)
2508
(void) png_setup_up_row(png_ptr, row_bytes, mins);
2509
best_row = png_ptr->try_row;
2512
else if ((filter_to_do & PNG_FILTER_UP) != 0)
2515
png_size_t lmins = mins;
2517
sum = png_setup_up_row(png_ptr, row_bytes, lmins);
2522
best_row = png_ptr->try_row;
2523
if (png_ptr->tst_row != NULL)
2525
png_ptr->try_row = png_ptr->tst_row;
2526
png_ptr->tst_row = best_row;
2532
if (filter_to_do == PNG_FILTER_AVG)
2534
(void) png_setup_avg_row(png_ptr, bpp, row_bytes, mins);
2535
best_row = png_ptr->try_row;
2538
else if ((filter_to_do & PNG_FILTER_AVG) != 0)
2541
png_size_t lmins = mins;
2543
sum= png_setup_avg_row(png_ptr, bpp, row_bytes, lmins);
2548
best_row = png_ptr->try_row;
2549
if (png_ptr->tst_row != NULL)
2551
png_ptr->try_row = png_ptr->tst_row;
2552
png_ptr->tst_row = best_row;
2558
if ((filter_to_do == PNG_FILTER_PAETH) != 0)
2560
(void) png_setup_paeth_row(png_ptr, bpp, row_bytes, mins);
2561
best_row = png_ptr->try_row;
2564
else if ((filter_to_do & PNG_FILTER_PAETH) != 0)
2567
png_size_t lmins = mins;
2569
sum = png_setup_paeth_row(png_ptr, bpp, row_bytes, lmins);
2573
best_row = png_ptr->try_row;
2574
if (png_ptr->tst_row != NULL)
2576
png_ptr->try_row = png_ptr->tst_row;
2577
png_ptr->tst_row = best_row;
2582
/* Do the actual writing of the filtered row data from the chosen filter. */
2583
png_write_filtered_row(png_ptr, best_row, row_info->rowbytes+1);
2585
#endif /* WRITE_FILTER */
2589
/* Do the actual writing of a previously filtered row. */
2591
png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
2592
png_size_t full_row_length/*includes filter byte*/)
2594
png_debug(1, "in png_write_filtered_row");
2596
png_debug1(2, "filter = %d", filtered_row[0]);
2598
png_compress_IDAT(png_ptr, filtered_row, full_row_length, Z_NO_FLUSH);
2600
#ifdef PNG_WRITE_FILTER_SUPPORTED
2601
/* Swap the current and previous rows */
2602
if (png_ptr->prev_row != NULL)
2606
tptr = png_ptr->prev_row;
2607
png_ptr->prev_row = png_ptr->row_buf;
2608
png_ptr->row_buf = tptr;
2610
#endif /* WRITE_FILTER */
2612
/* Finish row - updates counters and flushes zlib if last row */
2613
png_write_finish_row(png_ptr);
2615
#ifdef PNG_WRITE_FLUSH_SUPPORTED
2616
png_ptr->flush_rows++;
2618
if (png_ptr->flush_dist > 0 &&
2619
png_ptr->flush_rows >= png_ptr->flush_dist)
2621
png_write_flush(png_ptr);
2623
#endif /* WRITE_FLUSH */