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-rw-r--r--app/help/readpng.c275
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diff --git a/app/help/readpng.c b/app/help/readpng.c
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-/*---------------------------------------------------------------------------
-
- rpng - simple PNG display program readpng.c
-
- ---------------------------------------------------------------------------
-
- Copyright (c) 1998-1999 Greg Roelofs. All rights reserved.
-
- This software is provided "as is," without warranty of any kind,
- express or implied. In no event shall the author or contributors
- be held liable for any damages arising in any way from the use of
- this software.
-
- Permission is granted to anyone to use this software for any purpose,
- including commercial applications, and to alter it and redistribute
- it freely, subject to the following restrictions:
-
- 1. Redistributions of source code must retain the above copyright
- notice, disclaimer, and this list of conditions.
- 2. Redistributions in binary form must reproduce the above copyright
- notice, disclaimer, and this list of conditions in the documenta-
- tion and/or other materials provided with the distribution.
- 3. All advertising materials mentioning features or use of this
- software must display the following acknowledgment:
-
- This product includes software developed by Greg Roelofs
- and contributors for the book, "PNG: The Definitive Guide,"
- published by O'Reilly and Associates.
-
- ---------------------------------------------------------------------------*/
-
-#include <stdio.h>
-#include <stdlib.h>
-
-#include "png.h" /* libpng header; includes zlib.h */
-#include "readpng.h" /* typedefs, common macros, public prototypes */
-
-
-static png_structp png_ptr = NULL;
-static png_infop info_ptr = NULL;
-
-png_uint_32 width, height;
-int bit_depth, color_type;
-uch *image_data = NULL;
-
-
-void readpng_version_info()
-{
- fprintf(stderr, " Compiled with libpng %s; using libpng %s.\n",
- PNG_LIBPNG_VER_STRING, png_libpng_ver);
- fprintf(stderr, " Compiled with zlib %s; using zlib %s.\n",
- ZLIB_VERSION, zlib_version);
-}
-
-
-/* return value = 0 for success, 1 for bad sig, 2 for bad IHDR, 4 for no mem */
-
-int readpng_init(FILE *infile, long *pWidth, long *pHeight)
-{
- uch sig[8];
-
-
- /* first do a quick check that the file really is a PNG image; could
- * have used slightly more general png_sig_cmp() function instead */
-
- fread(sig, 1, 8, infile);
- if (!png_check_sig(sig, 8))
- return 1; /* bad signature */
-
-
- /* could pass pointers to user-defined error handlers instead of NULLs: */
-
- png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
- if (!png_ptr)
- return 4; /* out of memory */
-
- info_ptr = png_create_info_struct(png_ptr);
- if (!info_ptr) {
- png_destroy_read_struct(&png_ptr, NULL, NULL);
- return 4; /* out of memory */
- }
-
-
- /* we could create a second info struct here (end_info), but it's only
- * useful if we want to keep pre- and post-IDAT chunk info separated
- * (mainly for PNG-aware image editors and converters) */
-
-
- /* setjmp() must be called in every function that calls a PNG-reading
- * libpng function */
-
- if (setjmp(png_ptr->jmpbuf)) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- return 2;
- }
-
-
- png_init_io(png_ptr, infile);
- png_set_sig_bytes(png_ptr, 8); /* we already read the 8 signature bytes */
-
- png_read_info(png_ptr, info_ptr); /* read all PNG info up to image data */
-
-
- /* alternatively, could make separate calls to png_get_image_width(),
- * etc., but want bit_depth and color_type for later [don't care about
- * compression_type and filter_type => NULLs] */
-
- png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
- NULL, NULL, NULL);
- *pWidth = width;
- *pHeight = height;
-
-
- /* OK, that's all we need for now; return happy */
-
- return 0;
-}
-
-
-
-
-/* returns 0 if succeeds, 1 if fails due to no bKGD chunk, 2 if libpng error;
- * scales values to 8-bit if necessary */
-
-int readpng_get_bgcolor(uch *red, uch *green, uch *blue)
-{
- png_color_16p pBackground;
-
-
- /* setjmp() must be called in every function that calls a PNG-reading
- * libpng function */
-
- if (setjmp(png_ptr->jmpbuf)) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- return 2;
- }
-
-
- if (!png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
- return 1;
-
- /* it is not obvious from the libpng documentation, but this function
- * takes a pointer to a pointer, and it always returns valid red, green
- * and blue values, regardless of color_type: */
-
- png_get_bKGD(png_ptr, info_ptr, &pBackground);
-
-
- /* however, it always returns the raw bKGD data, regardless of any
- * bit-depth transformations, so check depth and adjust if necessary */
-
- if (bit_depth == 16) {
- *red = pBackground->red >> 8;
- *green = pBackground->green >> 8;
- *blue = pBackground->blue >> 8;
- } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
- if (bit_depth == 1)
- *red = *green = *blue = pBackground->gray? 255 : 0;
- else if (bit_depth == 2)
- *red = *green = *blue = (255/3) * pBackground->gray;
- else /* bit_depth == 4 */
- *red = *green = *blue = (255/15) * pBackground->gray;
- } else {
- *red = (uch)pBackground->red;
- *green = (uch)pBackground->green;
- *blue = (uch)pBackground->blue;
- }
-
- return 0;
-}
-
-
-
-
-/* display_exponent == LUT_exponent * CRT_exponent */
-
-uch *readpng_get_image(double display_exponent, int *pChannels, ulg *pRowbytes)
-{
- double gamma;
- png_uint_32 i, rowbytes;
- png_bytepp row_pointers = NULL;
-
-
- /* setjmp() must be called in every function that calls a PNG-reading
- * libpng function */
-
- if (setjmp(png_ptr->jmpbuf)) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- return NULL;
- }
-
-
- /* expand palette images to RGB, low-bit-depth grayscale images to 8 bits,
- * transparency chunks to full alpha channel; strip 16-bit-per-sample
- * images to 8 bits per sample; and convert grayscale to RGB[A] */
-
- if (color_type == PNG_COLOR_TYPE_PALETTE)
- png_set_expand(png_ptr);
- if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
- png_set_expand(png_ptr);
- if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
- png_set_expand(png_ptr);
- if (bit_depth == 16)
- png_set_strip_16(png_ptr);
- if (color_type == PNG_COLOR_TYPE_GRAY ||
- color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
- png_set_gray_to_rgb(png_ptr);
-
-
- /* unlike the example in the libpng documentation, we have *no* idea where
- * this file may have come from--so if it doesn't have a file gamma, don't
- * do any correction ("do no harm") */
-
- if (png_get_gAMA(png_ptr, info_ptr, &gamma))
- png_set_gamma(png_ptr, display_exponent, gamma);
-
-
- /* all transformations have been registered; now update info_ptr data,
- * get rowbytes and channels, and allocate image memory */
-
- png_read_update_info(png_ptr, info_ptr);
-
- *pRowbytes = rowbytes = png_get_rowbytes(png_ptr, info_ptr);
- *pChannels = (int)png_get_channels(png_ptr, info_ptr);
-
- if ((image_data = (uch *)malloc(rowbytes*height)) == NULL) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- return NULL;
- }
- if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- free(image_data);
- image_data = NULL;
- return NULL;
- }
-
- Trace((stderr, "readpng_get_image: rowbytes = %ld, height = %ld\n", rowbytes, height));
-
-
- /* set the individual row_pointers to point at the correct offsets */
-
- for (i = 0; i < height; ++i)
- row_pointers[height-1-i] = image_data + i*rowbytes;
-
-
- /* now we can go ahead and just read the whole image */
-
- png_read_image(png_ptr, row_pointers);
-
-
- /* and we're done! (png_read_end() can be omitted if no processing of
- * post-IDAT text/time/etc. is desired) */
-
- free(row_pointers);
- row_pointers = NULL;
-
- png_read_end(png_ptr, NULL);
-
- return image_data;
-}
-
-
-void readpng_cleanup(int free_image_data)
-{
- if (free_image_data && image_data) {
- free(image_data);
- image_data = NULL;
- }
-
- if (png_ptr && info_ptr) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- png_ptr = NULL;
- info_ptr = NULL;
- }
-}
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