| /*--------------------------------------------------------------------------- |
| |
| rpng - simple PNG display program readpng.c |
| |
| --------------------------------------------------------------------------- |
| |
| Copyright (c) 1998-2007 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. |
| |
| The contents of this file are DUAL-LICENSED. You may modify and/or |
| redistribute this software according to the terms of one of the |
| following two licenses (at your option): |
| |
| |
| LICENSE 1 ("BSD-like with advertising clause"): |
| |
| 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. |
| |
| |
| LICENSE 2 (GNU GPL v2 or later): |
| |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program; if not, write to the Free Software Foundation, |
| Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| |
| ---------------------------------------------------------------------------*/ |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| |
| #include "png.h" /* libpng header; includes zlib.h */ |
| #include "readpng.h" /* typedefs, common macros, public prototypes */ |
| |
| /* future versions of libpng will provide this macro: */ |
| #ifndef png_jmpbuf |
| # define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf) |
| #endif |
| |
| |
| 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(void) |
| { |
| 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, ulg *pWidth, ulg *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_sig_cmp(sig, 0, 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_jmpbuf(png_ptr))) { |
| 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_jmpbuf(png_ptr))) { |
| 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_jmpbuf(png_ptr))) { |
| 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: channels = %d, rowbytes = %ld, height = %ld\n", *pChannels, rowbytes, height)); |
| |
| |
| /* set the individual row_pointers to point at the correct offsets */ |
| |
| for (i = 0; i < height; ++i) |
| row_pointers[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; |
| } |
| } |
