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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@cworth.org>
*/
#include <stdio.h>
#include <stdlib.h>
#include <png.h>
#include "write_png.h"
static void
unpremultiply_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 *b = &data[i];
unsigned int pixel;
unsigned char alpha;
memcpy (&pixel, b, sizeof (unsigned int));
alpha = (pixel & 0xff000000) >> 24;
if (alpha == 0) {
b[0] = b[1] = b[2] = b[3] = 0;
} else {
b[0] = (((pixel & 0x0000ff) >> 0) * 255 + alpha / 2) / alpha;
b[1] = (((pixel & 0x00ff00) >> 8) * 255 + alpha / 2) / alpha;
b[2] = (((pixel & 0xff0000) >> 16) * 255 + alpha / 2) / alpha;
b[3] = alpha;
}
}
}
void
write_png_argb32 (char *buffer, FILE *file,
int width, int height, int stride)
{
int i;
png_struct *png;
png_info *info;
png_byte **rows;
png_color_16 white;
rows = malloc (height * sizeof(png_byte*));
for (i = 0; i < height; i++) {
rows[i] = buffer + i * stride;
}
png = png_create_write_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
info = png_create_info_struct (png);
png_init_io (png, file);
png_set_IHDR (png, info,
width, height, 8,
PNG_COLOR_TYPE_RGB_ALPHA,
PNG_INTERLACE_NONE,
PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
white.red = 0xff;
white.blue = 0xff;
white.green = 0xff;
png_set_bKGD (png, info, &white);
png_set_write_user_transform_fn (png, unpremultiply_data);
png_set_bgr (png);
png_write_info (png, info);
png_write_image (png, rows);
png_write_end (png, info);
png_destroy_write_struct (&png, &info);
free (rows);
}
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