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* Copyright (C) 1994-1996, Thomas G. Lane.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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* This file contains code for merged upsampling/color conversion.
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* This file combines functions from jdsample.c and jdcolor.c;
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* read those files first to understand what's going on.
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* When the chroma components are to be upsampled by simple replication
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* (ie, box filtering), we can save some work in color conversion by
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* calculating all the output pixels corresponding to a pair of chroma
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* samples at one time. In the conversion equations
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* G = Y + K2 * Cb + K3 * Cr
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* only the Y term varies among the group of pixels corresponding to a pair
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* of chroma samples, so the rest of the terms can be calculated just once.
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* At typical sampling ratios, this eliminates half or three-quarters of the
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* multiplications needed for color conversion.
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* This file currently provides implementations for the following cases:
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* YCbCr => RGB color conversion only.
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* Sampling ratios of 2h1v or 2h2v.
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* No scaling needed at upsample time.
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* Corner-aligned (non-CCIR601) sampling alignment.
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* Other special cases could be added, but in most applications these are
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* the only common cases. (For uncommon cases we fall back on the more
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* general code in jdsample.c and jdcolor.c.)
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#define JPEG_INTERNALS
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#ifdef UPSAMPLE_MERGING_SUPPORTED
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/* Private subobject */
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struct jpeg_upsampler pub; /* public fields */
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/* Pointer to routine to do actual upsampling/conversion of one row group */
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JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
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JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
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JSAMPARRAY output_buf));
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/* Private state for YCC->RGB conversion */
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int * Cr_r_tab; /* => table for Cr to R conversion */
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int * Cb_b_tab; /* => table for Cb to B conversion */
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INT32 * Cr_g_tab; /* => table for Cr to G conversion */
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INT32 * Cb_g_tab; /* => table for Cb to G conversion */
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/* For 2:1 vertical sampling, we produce two output rows at a time.
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* We need a "spare" row buffer to hold the second output row if the
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* application provides just a one-row buffer; we also use the spare
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* to discard the dummy last row if the image height is odd.
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boolean spare_full; /* T if spare buffer is occupied */
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JDIMENSION out_row_width; /* samples per output row */
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JDIMENSION rows_to_go; /* counts rows remaining in image */
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typedef my_upsampler * my_upsample_ptr;
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#define SCALEBITS 16 /* speediest right-shift on some machines */
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#define ONE_HALF ((INT32) 1 << (SCALEBITS-1))
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#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
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* Initialize tables for YCC->RGB colorspace conversion.
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* This is taken directly from jdcolor.c; see that file for more info.
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build_ycc_rgb_table (j_decompress_ptr cinfo)
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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upsample->Cr_r_tab = (int *)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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(MAXJSAMPLE+1) * SIZEOF(int));
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upsample->Cb_b_tab = (int *)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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(MAXJSAMPLE+1) * SIZEOF(int));
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upsample->Cr_g_tab = (INT32 *)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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(MAXJSAMPLE+1) * SIZEOF(INT32));
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upsample->Cb_g_tab = (INT32 *)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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(MAXJSAMPLE+1) * SIZEOF(INT32));
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for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
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/* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
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/* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
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/* Cr=>R value is nearest int to 1.40200 * x */
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upsample->Cr_r_tab[i] = (int)
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RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
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/* Cb=>B value is nearest int to 1.77200 * x */
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upsample->Cb_b_tab[i] = (int)
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RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
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/* Cr=>G value is scaled-up -0.71414 * x */
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upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
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/* Cb=>G value is scaled-up -0.34414 * x */
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/* We also add in ONE_HALF so that need not do it in inner loop */
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upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
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* Initialize for an upsampling pass.
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start_pass_merged_upsample (j_decompress_ptr cinfo)
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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/* Mark the spare buffer empty */
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upsample->spare_full = FALSE;
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/* Initialize total-height counter for detecting bottom of image */
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upsample->rows_to_go = cinfo->output_height;
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* Control routine to do upsampling (and color conversion).
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* The control routine just handles the row buffering considerations.
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merged_2v_upsample (j_decompress_ptr cinfo,
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JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
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JDIMENSION in_row_groups_avail,
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JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
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JDIMENSION out_rows_avail)
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/* 2:1 vertical sampling case: may need a spare row. */
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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JSAMPROW work_ptrs[2];
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JDIMENSION num_rows; /* number of rows returned to caller */
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if (upsample->spare_full) {
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/* If we have a spare row saved from a previous cycle, just return it. */
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jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
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1, upsample->out_row_width);
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upsample->spare_full = FALSE;
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/* Figure number of rows to return to caller. */
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/* Not more than the distance to the end of the image. */
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if (num_rows > upsample->rows_to_go)
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num_rows = upsample->rows_to_go;
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/* And not more than what the client can accept: */
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out_rows_avail -= *out_row_ctr;
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if (num_rows > out_rows_avail)
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num_rows = out_rows_avail;
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/* Create output pointer array for upsampler. */
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work_ptrs[0] = output_buf[*out_row_ctr];
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work_ptrs[1] = output_buf[*out_row_ctr + 1];
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work_ptrs[1] = upsample->spare_row;
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upsample->spare_full = TRUE;
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/* Now do the upsampling. */
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(*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
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*out_row_ctr += num_rows;
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upsample->rows_to_go -= num_rows;
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/* When the buffer is emptied, declare this input row group consumed */
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if (! upsample->spare_full)
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(*in_row_group_ctr)++;
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merged_1v_upsample (j_decompress_ptr cinfo,
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JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
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JDIMENSION in_row_groups_avail,
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JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
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JDIMENSION out_rows_avail)
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/* 1:1 vertical sampling case: much easier, never need a spare row. */
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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/* Just do the upsampling. */
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(*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
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output_buf + *out_row_ctr);
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(*in_row_group_ctr)++;
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* These are the routines invoked by the control routines to do
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* the actual upsampling/conversion. One row group is processed per call.
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* Note: since we may be writing directly into application-supplied buffers,
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* we have to be honest about the output width; we can't assume the buffer
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* has been rounded up to an even width.
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* Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
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h2v1_merged_upsample (j_decompress_ptr cinfo,
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JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
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JSAMPARRAY output_buf)
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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register int y, cred, cgreen, cblue;
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register JSAMPROW outptr;
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JSAMPROW inptr0, inptr1, inptr2;
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/* copy these pointers into registers if possible */
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register JSAMPLE * range_limit = cinfo->sample_range_limit;
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int * Crrtab = upsample->Cr_r_tab;
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int * Cbbtab = upsample->Cb_b_tab;
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INT32 * Crgtab = upsample->Cr_g_tab;
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INT32 * Cbgtab = upsample->Cb_g_tab;
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inptr0 = input_buf[0][in_row_group_ctr];
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inptr1 = input_buf[1][in_row_group_ctr];
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inptr2 = input_buf[2][in_row_group_ctr];
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outptr = output_buf[0];
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/* Loop for each pair of output pixels */
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for (col = cinfo->output_width >> 1; col > 0; col--) {
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/* Do the chroma part of the calculation */
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cb = GETJSAMPLE(*inptr1++);
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cr = GETJSAMPLE(*inptr2++);
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cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
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/* Fetch 2 Y values and emit 2 pixels */
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y = GETJSAMPLE(*inptr0++);
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outptr[RGB_RED] = range_limit[y + cred];
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outptr[RGB_GREEN] = range_limit[y + cgreen];
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outptr[RGB_BLUE] = range_limit[y + cblue];
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outptr += RGB_PIXELSIZE;
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y = GETJSAMPLE(*inptr0++);
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outptr[RGB_RED] = range_limit[y + cred];
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outptr[RGB_GREEN] = range_limit[y + cgreen];
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outptr[RGB_BLUE] = range_limit[y + cblue];
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outptr += RGB_PIXELSIZE;
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/* If image width is odd, do the last output column separately */
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if (cinfo->output_width & 1) {
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cb = GETJSAMPLE(*inptr1);
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cr = GETJSAMPLE(*inptr2);
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cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
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y = GETJSAMPLE(*inptr0);
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outptr[RGB_RED] = range_limit[y + cred];
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outptr[RGB_GREEN] = range_limit[y + cgreen];
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outptr[RGB_BLUE] = range_limit[y + cblue];
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* Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
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h2v2_merged_upsample (j_decompress_ptr cinfo,
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JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
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JSAMPARRAY output_buf)
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my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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register int y, cred, cgreen, cblue;
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register JSAMPROW outptr0, outptr1;
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JSAMPROW inptr00, inptr01, inptr1, inptr2;
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/* copy these pointers into registers if possible */
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register JSAMPLE * range_limit = cinfo->sample_range_limit;
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int * Crrtab = upsample->Cr_r_tab;
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int * Cbbtab = upsample->Cb_b_tab;
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INT32 * Crgtab = upsample->Cr_g_tab;
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INT32 * Cbgtab = upsample->Cb_g_tab;
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inptr00 = input_buf[0][in_row_group_ctr*2];
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inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
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inptr1 = input_buf[1][in_row_group_ctr];
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inptr2 = input_buf[2][in_row_group_ctr];
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outptr0 = output_buf[0];
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outptr1 = output_buf[1];
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/* Loop for each group of output pixels */
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for (col = cinfo->output_width >> 1; col > 0; col--) {
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/* Do the chroma part of the calculation */
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cb = GETJSAMPLE(*inptr1++);
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cr = GETJSAMPLE(*inptr2++);
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cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
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/* Fetch 4 Y values and emit 4 pixels */
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y = GETJSAMPLE(*inptr00++);
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outptr0[RGB_RED] = range_limit[y + cred];
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outptr0[RGB_GREEN] = range_limit[y + cgreen];
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outptr0[RGB_BLUE] = range_limit[y + cblue];
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outptr0 += RGB_PIXELSIZE;
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y = GETJSAMPLE(*inptr00++);
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outptr0[RGB_RED] = range_limit[y + cred];
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outptr0[RGB_GREEN] = range_limit[y + cgreen];
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outptr0[RGB_BLUE] = range_limit[y + cblue];
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outptr0 += RGB_PIXELSIZE;
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y = GETJSAMPLE(*inptr01++);
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outptr1[RGB_RED] = range_limit[y + cred];
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outptr1[RGB_GREEN] = range_limit[y + cgreen];
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outptr1[RGB_BLUE] = range_limit[y + cblue];
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outptr1 += RGB_PIXELSIZE;
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y = GETJSAMPLE(*inptr01++);
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outptr1[RGB_RED] = range_limit[y + cred];
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outptr1[RGB_GREEN] = range_limit[y + cgreen];
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outptr1[RGB_BLUE] = range_limit[y + cblue];
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outptr1 += RGB_PIXELSIZE;
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/* If image width is odd, do the last output column separately */
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if (cinfo->output_width & 1) {
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cb = GETJSAMPLE(*inptr1);
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cr = GETJSAMPLE(*inptr2);
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cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
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y = GETJSAMPLE(*inptr00);
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outptr0[RGB_RED] = range_limit[y + cred];
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outptr0[RGB_GREEN] = range_limit[y + cgreen];
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outptr0[RGB_BLUE] = range_limit[y + cblue];
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y = GETJSAMPLE(*inptr01);
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outptr1[RGB_RED] = range_limit[y + cred];
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outptr1[RGB_GREEN] = range_limit[y + cgreen];
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outptr1[RGB_BLUE] = range_limit[y + cblue];
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* Module initialization routine for merged upsampling/color conversion.
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* NB: this is called under the conditions determined by use_merged_upsample()
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* in jdmaster.c. That routine MUST correspond to the actual capabilities
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* of this module; no safety checks are made here.
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jinit_merged_upsampler (j_decompress_ptr cinfo)
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my_upsample_ptr upsample;
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upsample = (my_upsample_ptr)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(my_upsampler));
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cinfo->upsample = (struct jpeg_upsampler *) upsample;
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upsample->pub.start_pass = start_pass_merged_upsample;
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upsample->pub.need_context_rows = FALSE;
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upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
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if (cinfo->max_v_samp_factor == 2) {
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upsample->pub.upsample = merged_2v_upsample;
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upsample->upmethod = h2v2_merged_upsample;
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/* Allocate a spare row buffer */
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upsample->spare_row = (JSAMPROW)
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(*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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(size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
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upsample->pub.upsample = merged_1v_upsample;
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upsample->upmethod = h2v1_merged_upsample;
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/* No spare row needed */
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upsample->spare_row = NULL;
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build_ycc_rgb_table(cinfo);
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#endif /* UPSAMPLE_MERGING_SUPPORTED */
added
removed
jpeg/jdmerge.c
