pngw.cpp

/*
 *
 * 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
*/

#include <png.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include "pngw.h"

#define FH_ERROR_OK 0
#define FH_ERROR_FILE 1		/* read/access error */
#define FH_ERROR_FORMAT 2	/* file format error */
#define FH_ERROR_MALLOC 3	/* error during malloc */
#define PNG_BYTES_TO_CHECK 4
#define min(x,y) ((x) < (y) ? (x) : (y))

int fh_png_load(const char *name, unsigned char **buffer, int* xp, int* yp);

int fh_png_id(const char *name)
{
	int fd;
	char id[4];
	fd=open(name,O_RDONLY); if(fd==-1) return(0);
	read(fd,id,4);
	close(fd);
	if(id[1]=='P' && id[2]=='N' && id[3]=='G') return(1);
	return(0);
}

int fh_png_load(const char *name, unsigned char **buffer, int* xp, int* yp);

int int_png_load(const char *name, unsigned char **buffer, int* xp, int* yp, int* bpp, bool alpha)
{
	static const png_color_16 my_background = {0, 0, 0, 0, 0};
	png_structp png_ptr;
	png_infop info_ptr;
	png_uint_32 width, height;
	unsigned int i;
	int bit_depth, color_type, interlace_type, number_passes, pass, int_bpp;
	png_byte * fbptr;
	FILE     * fh;
	bool updateInfo_alreadyRead;

	if(!(fh=fopen(name,"rb")))
		return(FH_ERROR_FILE);
	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
	if(png_ptr == NULL) {
		fclose(fh);
		return(FH_ERROR_FORMAT);
	}
	info_ptr = png_create_info_struct(png_ptr);
	if(info_ptr == NULL)
	{
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		fclose(fh);
		return(FH_ERROR_FORMAT);
	}
#if (PNG_LIBPNG_VER < 10500)
	if (setjmp(png_ptr->jmpbuf))
#else
	if (setjmp(png_jmpbuf(png_ptr)))
#endif
	{
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		fclose(fh);
		return(FH_ERROR_FORMAT);
	}
	png_init_io(png_ptr,fh);
	png_read_info(png_ptr, info_ptr);
	png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, NULL, NULL);
	updateInfo_alreadyRead = false;
	if (alpha) // 24bit or gray scale PNGs with alpha-channel
	{
		*bpp = png_get_channels(png_ptr, info_ptr);
		if ((*bpp == 2) && (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)) {
			if (bit_depth < 8) {
				/* Extract multiple pixels with bit depths of 1, 2, and 4
				   from a single byte into separate bytes
				   (useful for paletted and grayscale images). */
				png_set_packing(png_ptr);
				/* Expand grayscale images to the full 8 bits
				   from 1, 2, or 4 bits/pixel */
#if PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR <= 2 && PNG_LIBPNG_VER_RELEASE < 9
				png_set_gray_1_2_4_to_8(png_ptr);
#else
				png_set_expand_gray_1_2_4_to_8(png_ptr);
#endif
			}
			/* Expand the grayscale to 24-bit RGB if necessary. */
			png_set_gray_to_rgb(png_ptr);
			/* Update the users info structure */
			png_read_update_info(png_ptr, info_ptr);
			updateInfo_alreadyRead = true;
			*bpp = png_get_channels(png_ptr, info_ptr);
			if (*bpp != 4) {
				/* No 4 channels found
				   load PNG without alpha channel */
				png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
				fclose(fh);
				return fh_png_load(name, buffer, xp, yp);
			}
		}
		else if ((*bpp != 4) || !(color_type & PNG_COLOR_MASK_ALPHA)) {
			/* No 4 channels & not an alpha channel found
			   load PNG without alpha channel */
			png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
			fclose(fh);
			return fh_png_load(name, buffer, xp, yp);
		}
		int_bpp = 4;

		/* Expand paletted or RGB images with transparency
		   to full alpha channels so the data will
		   be available as RGBA quartets. */
		if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
			png_set_tRNS_to_alpha(png_ptr);
	}else // All other PNGs
	{
		if (color_type == PNG_COLOR_TYPE_PALETTE)
		{
			png_set_palette_to_rgb(png_ptr);
			png_set_background(png_ptr, (png_color_16*)&my_background, PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
			/* other possibility for png_set_background: use png_get_bKGD */
		}
		if (color_type == PNG_COLOR_TYPE_GRAY        ||
		    color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
		{
			png_set_gray_to_rgb(png_ptr);
			png_set_background(png_ptr, (png_color_16*)&my_background, PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
		}
		/* this test does not trigger for 8bit-paletted PNGs with newer libpng (1.2.36 at least),
	   	   but the data delivered is with alpha channel anyway, so always strip alpha for now
		 */
#if PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR <= 2 && PNG_LIBPNG_VER_RELEASE < 36
		if (color_type & PNG_COLOR_MASK_ALPHA)
#endif
			png_set_strip_alpha(png_ptr);
		if (bit_depth < 8)
			png_set_packing(png_ptr);
		int_bpp = 3;
	}
	if (bit_depth == 16)
		png_set_strip_16(png_ptr);
	number_passes = png_set_interlace_handling(png_ptr);
	/* Update the users info structure */
	if (updateInfo_alreadyRead == 0)
		png_read_update_info(png_ptr,info_ptr);
	unsigned long rowbytes = png_get_rowbytes(png_ptr, info_ptr);
	if (width * int_bpp != rowbytes)
	{
		printf("[pngw.cpp]: Error processing %s - please report (including image).\n", name);
		printf("           width: %lu rowbytes: %lu\n", (unsigned long)width, (unsigned long)rowbytes);
		fclose(fh);
		return(FH_ERROR_FORMAT);
	}
	for (pass = 0; pass < number_passes; pass++)
	{
		fbptr = (png_byte *)(*buffer);
		for (i = 0; i < height; i++, fbptr += width * int_bpp)
			png_read_row(png_ptr, fbptr, NULL);
	}
	png_read_end(png_ptr, info_ptr);
	png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
	fclose(fh);
	return(FH_ERROR_OK);
}

int png_load_ext(const char *name, unsigned char **buffer, int* xp, int* yp, int* bpp)
{
	return int_png_load(name, buffer, xp, yp, bpp, true);
}

int fh_png_load(const char *name, unsigned char **buffer, int* xp, int* yp)
{
	return int_png_load(name, buffer, xp, yp, NULL, false);
}

int fh_png_getsize(const char *name,int *x,int *y)
{
	png_structp png_ptr;
	png_infop info_ptr;
	png_uint_32 width, height;
	int bit_depth, color_type, interlace_type;
	FILE *fh;

	if(!(fh=fopen(name,"rb")))	return(FH_ERROR_FILE);

	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,NULL,NULL,NULL);
	if(png_ptr == NULL) {
		fclose(fh);
		return(FH_ERROR_FORMAT);
	}
	info_ptr = png_create_info_struct(png_ptr);
	if(info_ptr == NULL)
	{
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		fclose(fh);
		return(FH_ERROR_FORMAT);
	}

#if (PNG_LIBPNG_VER < 10500)
	if (setjmp(png_ptr->jmpbuf))
#else
	if (setjmp(png_jmpbuf(png_ptr)))
#endif
	{
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		fclose(fh);
		return(FH_ERROR_FORMAT);
	}

	png_init_io(png_ptr,fh);
	png_read_info(png_ptr, info_ptr);
	png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,&interlace_type, NULL, NULL);
	png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
	*x=width;
	*y=height;
	fclose(fh);
	return(FH_ERROR_OK);
}