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/*
* Copyright © 2003 USC, Information Sciences Institute
*
* Permission to use, copy, modify, distribute, and sell this software
* and its documentation for any purpose is hereby granted without
* fee, provided that the above copyright notice appear in all copies
* and that both that copyright notice and this permission notice
* appear in supporting documentation, and that the name of the
* University of Southern California not be used in advertising or
* publicity pertaining to distribution of the software without
* specific, written prior permission. The University of Southern
* California makes no representations about the suitability of this
* software for any purpose. It is provided "as is" without express
* or implied warranty.
*
* THE UNIVERSITY OF SOUTHERN CALIFORNIA DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE UNIVERSITY OF
* SOUTHERN CALIFORNIA BE LIABLE FOR ANY SPECIAL, INDIRECT OR
* CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
* OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
* NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* Author: Carl D. Worth <cworth@isi.edu>
*/
#include <stdio.h>
#include <stdlib.h>
#include <png.h>
#include "read_png.h"
#include "xmalloc.h"
static void
premultiply_data (png_structp png,
png_row_infop row_info,
png_bytep data)
{
int i;
for (i = 0; i < row_info->rowbytes; i += 4) {
unsigned char *base = &data[i];
unsigned char blue = base[0];
unsigned char green = base[1];
unsigned char red = base[2];
unsigned char alpha = base[3];
unsigned long p;
red = ((unsigned) red * (unsigned) alpha + 127) / 255;
green = ((unsigned) green * (unsigned) alpha + 127) / 255;
blue = ((unsigned) blue * (unsigned) alpha + 127) / 255;
p = (alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
memcpy (base, &p, sizeof (unsigned long));
}
}
read_png_status_t
read_png_argb32 (const char *filename,
unsigned char **data,
unsigned int *width,
unsigned int *height,
unsigned int *stride)
{
int i;
FILE *file;
static const int PNG_SIG_SIZE = 8;
unsigned char png_sig[PNG_SIG_SIZE];
int sig_bytes;
png_struct *png;
png_info *info;
png_uint_32 png_width, png_height;
int depth, color_type, interlace;
unsigned int pixel_size;
png_byte **row_pointers;
file = fopen (filename, "rb");
if (file == NULL) {
return READ_PNG_FILE_NOT_FOUND;
}
sig_bytes = fread (png_sig, 1, PNG_SIG_SIZE, file);
if (png_check_sig (png_sig, sig_bytes) == 0) {
fclose (file);
return READ_PNG_FILE_NOT_PNG;
}
/* XXX: Perhaps we'll want some other error handlers? */
png = png_create_read_struct (PNG_LIBPNG_VER_STRING,
NULL,
NULL,
NULL);
if (png == NULL) {
fclose (file);
return READ_PNG_NO_MEMORY;
}
info = png_create_info_struct (png);
if (info == NULL) {
fclose (file);
png_destroy_read_struct (&png, NULL, NULL);
return READ_PNG_NO_MEMORY;
}
png_init_io (png, file);
png_set_sig_bytes (png, sig_bytes);
png_read_info (png, info);
png_get_IHDR (png, info,
&png_width, &png_height, &depth,
&color_type, &interlace, NULL, NULL);
*width = png_width;
*height = png_height;
*stride = 4 * png_width;
/* convert palette/gray image to rgb */
if (color_type == PNG_COLOR_TYPE_PALETTE)
png_set_palette_to_rgb (png);
/* expand gray bit depth if needed */
if (color_type == PNG_COLOR_TYPE_GRAY && depth < 8)
png_set_gray_1_2_4_to_8 (png);
/* transform transparency to alpha */
if (png_get_valid(png, info, PNG_INFO_tRNS))
png_set_tRNS_to_alpha (png);
if (depth == 16)
png_set_strip_16 (png);
if (depth < 8)
png_set_packing (png);
/* convert grayscale to RGB */
if (color_type == PNG_COLOR_TYPE_GRAY
|| color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
png_set_gray_to_rgb (png);
if (interlace != PNG_INTERLACE_NONE)
png_set_interlace_handling (png);
png_set_bgr (png);
png_set_filler (png, 0xff, PNG_FILLER_AFTER);
png_set_read_user_transform_fn (png, premultiply_data);
png_read_update_info (png, info);
pixel_size = 4;
*data = xmalloc (png_width * png_height * pixel_size);
row_pointers = malloc (png_height * sizeof(char *));
for (i=0; i < png_height; i++)
row_pointers[i] = (png_byte *) (*data + i * png_width * pixel_size);
png_read_image (png, row_pointers);
png_read_end (png, info);
free (row_pointers);
fclose (file);
png_destroy_read_struct (&png, &info, NULL);
return READ_PNG_SUCCESS;
}
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