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//-------------------------------------
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// PNGFILE.C -- Image File Functions
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//-------------------------------------
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// Copyright 2000, Willem van Schaik.
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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
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define_exception_type(const char *);
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extern struct exception_context the_exception_context[1];
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struct exception_context the_exception_context[1];
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static OPENFILENAME ofn;
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static png_structp png_ptr = NULL;
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static png_infop info_ptr = NULL;
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png_cexcept_error(png_structp png_ptr, png_const_charp msg)
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#ifdef PNG_CONSOLE_IO_SUPPORTED
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fprintf(stderr, "libpng error: %s\n", msg);
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// Windows open-file functions
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void PngFileInitialize (HWND hwnd)
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static TCHAR szFilter[] = TEXT ("PNG Files (*.PNG)\0*.png\0")
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TEXT ("All Files (*.*)\0*.*\0\0");
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ofn.lStructSize = sizeof (OPENFILENAME);
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ofn.lpstrFilter = szFilter;
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ofn.lpstrCustomFilter = NULL;
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ofn.nMaxCustFilter = 0;
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ofn.lpstrFile = NULL; // Set in Open and Close functions
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ofn.nMaxFile = MAX_PATH;
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ofn.lpstrFileTitle = NULL; // Set in Open and Close functions
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ofn.nMaxFileTitle = MAX_PATH;
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ofn.lpstrInitialDir = NULL;
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ofn.lpstrTitle = NULL;
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ofn.Flags = 0; // Set in Open and Close functions
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ofn.nFileExtension = 0;
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ofn.lpstrDefExt = TEXT ("png");
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ofn.lpTemplateName = NULL;
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BOOL PngFileOpenDlg (HWND hwnd, PTSTR pstrFileName, PTSTR pstrTitleName)
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ofn.lpstrFile = pstrFileName;
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ofn.lpstrFileTitle = pstrTitleName;
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ofn.Flags = OFN_HIDEREADONLY;
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return GetOpenFileName (&ofn);
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BOOL PngFileSaveDlg (HWND hwnd, PTSTR pstrFileName, PTSTR pstrTitleName)
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ofn.lpstrFile = pstrFileName;
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ofn.lpstrFileTitle = pstrTitleName;
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ofn.Flags = OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT;
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return GetSaveFileName (&ofn);
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// PNG image handler functions
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BOOL PngLoadImage (PTSTR pstrFileName, png_byte **ppbImageData,
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int *piWidth, int *piHeight, int *piChannels, png_color *pBkgColor)
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png_color_16 *pBackground;
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png_uint_32 ulChannels;
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png_uint_32 ulRowBytes;
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png_byte *pbImageData = *ppbImageData;
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static png_byte **ppbRowPointers = NULL;
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// open the PNG input file
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*ppbImageData = pbImageData = NULL;
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if (!(pfFile = fopen(pstrFileName, "rb")))
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*ppbImageData = pbImageData = NULL;
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// first check the eight byte PNG signature
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fread(pbSig, 1, 8, pfFile);
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if (png_sig_cmp(pbSig, 0, 8))
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*ppbImageData = pbImageData = NULL;
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// create the two png(-info) structures
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png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL,
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(png_error_ptr)png_cexcept_error, (png_error_ptr)NULL);
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*ppbImageData = pbImageData = NULL;
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info_ptr = png_create_info_struct(png_ptr);
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png_destroy_read_struct(&png_ptr, NULL, NULL);
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*ppbImageData = pbImageData = NULL;
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// initialize the png structure
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#ifdef PNG_STDIO_SUPPORTED
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png_init_io(png_ptr, pfFile);
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png_set_read_fn(png_ptr, (png_voidp)pfFile, png_read_data);
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png_set_sig_bytes(png_ptr, 8);
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// read all PNG info up to image data
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png_read_info(png_ptr, info_ptr);
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// get width, height, bit-depth and color-type
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png_get_IHDR(png_ptr, info_ptr, piWidth, piHeight, &iBitDepth,
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&iColorType, NULL, NULL, NULL);
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// expand images of all color-type and bit-depth to 3x8 bit RGB images
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// let the library process things like alpha, transparency, background
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png_set_strip_16(png_ptr);
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if (iColorType == PNG_COLOR_TYPE_PALETTE)
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png_set_expand(png_ptr);
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png_set_expand(png_ptr);
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if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
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png_set_expand(png_ptr);
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if (iColorType == PNG_COLOR_TYPE_GRAY ||
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iColorType == PNG_COLOR_TYPE_GRAY_ALPHA)
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png_set_gray_to_rgb(png_ptr);
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// set the background color to draw transparent and alpha images over.
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if (png_get_bKGD(png_ptr, info_ptr, &pBackground))
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png_set_background(png_ptr, pBackground, PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
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pBkgColor->red = (byte) pBackground->red;
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pBkgColor->green = (byte) pBackground->green;
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pBkgColor->blue = (byte) pBackground->blue;
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// if required set gamma conversion
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if (png_get_gAMA(png_ptr, info_ptr, &dGamma))
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png_set_gamma(png_ptr, (double) 2.2, dGamma);
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// after the transformations have been registered update info_ptr data
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png_read_update_info(png_ptr, info_ptr);
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// get again width, height and the new bit-depth and color-type
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png_get_IHDR(png_ptr, info_ptr, piWidth, piHeight, &iBitDepth,
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&iColorType, NULL, NULL, NULL);
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// row_bytes is the width x number of channels
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ulRowBytes = png_get_rowbytes(png_ptr, info_ptr);
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ulChannels = png_get_channels(png_ptr, info_ptr);
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*piChannels = ulChannels;
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// now we can allocate memory to store the image
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if ((pbImageData = (png_byte *) malloc(ulRowBytes * (*piHeight)
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* sizeof(png_byte))) == NULL)
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png_error(png_ptr, "Visual PNG: out of memory");
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*ppbImageData = pbImageData;
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// and allocate memory for an array of row-pointers
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if ((ppbRowPointers = (png_bytepp) malloc((*piHeight)
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* sizeof(png_bytep))) == NULL)
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png_error(png_ptr, "Visual PNG: out of memory");
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// set the individual row-pointers to point at the correct offsets
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for (i = 0; i < (*piHeight); i++)
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ppbRowPointers[i] = pbImageData + i * ulRowBytes;
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// now we can go ahead and just read the whole image
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png_read_image(png_ptr, ppbRowPointers);
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// read the additional chunks in the PNG file (not really needed)
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png_read_end(png_ptr, NULL);
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free (ppbRowPointers);
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ppbRowPointers = NULL;
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png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
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*ppbImageData = pbImageData = NULL;
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free (ppbRowPointers);
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BOOL PngSaveImage (PTSTR pstrFileName, png_byte *pDiData,
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int iWidth, int iHeight, png_color bkgColor)
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const int ciBitDepth = 8;
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const int ciChannels = 3;
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png_uint_32 ulRowBytes;
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static png_byte **ppbRowPointers = NULL;
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// open the PNG output file
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if (!(pfFile = fopen(pstrFileName, "wb")))
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// prepare the standard PNG structures
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png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL,
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(png_error_ptr)png_cexcept_error, (png_error_ptr)NULL);
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info_ptr = png_create_info_struct(png_ptr);
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png_destroy_write_struct(&png_ptr, (png_infopp) NULL);
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// initialize the png structure
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#ifdef PNG_STDIO_SUPPORTED
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png_init_io(png_ptr, pfFile);
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png_set_write_fn(png_ptr, (png_voidp)pfFile, png_write_data, png_flush);
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// we're going to write a very simple 3x8 bit RGB image
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png_set_IHDR(png_ptr, info_ptr, iWidth, iHeight, ciBitDepth,
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PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
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PNG_FILTER_TYPE_BASE);
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// write the file header information
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png_write_info(png_ptr, info_ptr);
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// swap the BGR pixels in the DiData structure to RGB
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png_set_bgr(png_ptr);
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// row_bytes is the width x number of channels
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ulRowBytes = iWidth * ciChannels;
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// we can allocate memory for an array of row-pointers
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if ((ppbRowPointers = (png_bytepp) malloc(iHeight * sizeof(png_bytep))) == NULL)
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Throw "Visualpng: Out of memory";
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// set the individual row-pointers to point at the correct offsets
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for (i = 0; i < iHeight; i++)
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ppbRowPointers[i] = pDiData + i * (((ulRowBytes + 3) >> 2) << 2);
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// write out the entire image data in one call
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png_write_image (png_ptr, ppbRowPointers);
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// write the additional chunks to the PNG file (not really needed)
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png_write_end(png_ptr, info_ptr);
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free (ppbRowPointers);
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ppbRowPointers = NULL;
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// clean up after the write, and free any memory allocated
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png_destroy_write_struct(&png_ptr, (png_infopp) NULL);
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png_destroy_write_struct(&png_ptr, (png_infopp) NULL);
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free (ppbRowPointers);
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#ifndef PNG_STDIO_SUPPORTED
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png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
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/* fread() returns 0 on error, so it is OK to store this in a png_size_t
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* instead of an int, which is what fread() actually returns.
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check = (png_size_t)fread(data, (png_size_t)1, length,
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(FILE *)png_ptr->io_ptr);
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png_error(png_ptr, "Read Error");
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png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
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check = fwrite(data, 1, length, (FILE *)(png_ptr->io_ptr));
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png_error(png_ptr, "Write Error");
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png_flush(png_structp png_ptr)
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io_ptr = (FILE *)CVT_PTR((png_ptr->io_ptr));