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Diffstat (limited to 'libpng/contrib/gregbook/readpng.c')
| -rw-r--r-- | libpng/contrib/gregbook/readpng.c | 323 |
1 files changed, 323 insertions, 0 deletions
diff --git a/libpng/contrib/gregbook/readpng.c b/libpng/contrib/gregbook/readpng.c new file mode 100644 index 00000000..fad9b536 --- /dev/null +++ b/libpng/contrib/gregbook/readpng.c @@ -0,0 +1,323 @@ +/*--------------------------------------------------------------------------- + + rpng - simple PNG display program readpng.c + + --------------------------------------------------------------------------- + + Copyright (c) 1998-2007,2017 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 <zlib.h> + +#include "png.h" /* libpng header */ +#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_get_libpng_ver(NULL), 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))) { + free(image_data); + image_data = NULL; + free(row_pointers); + row_pointers = NULL; + 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); +#ifdef PNG_READ_16_TO_8_SUPPORTED + if (bit_depth == 16) +# ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED + png_set_scale_16(png_ptr); +# else + png_set_strip_16(png_ptr); +# endif +#endif + 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); + + /* Guard against integer overflow */ + if (height > ((size_t)(-1))/rowbytes) { + fprintf(stderr, "readpng: image_data buffer would be too large\n", + return NULL; + } + + 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; + } +} |