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/* cairo - a vector graphics library with display and print output
*
* Copyright © 2003 University of Southern California
*
* This library is free software; you can redistribute it and/or
* modify it either under the terms of the GNU Lesser General Public
* License version 2.1 as published by the Free Software Foundation
* (the "LGPL") or, at your option, under the terms of the Mozilla
* Public License Version 1.1 (the "MPL"). If you do not alter this
* notice, a recipient may use your version of this file under either
* the MPL or the LGPL.
*
* You should have received a copy of the LGPL along with this library
* in the file COPYING-LGPL-2.1; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
* You should have received a copy of the MPL along with this library
* in the file COPYING-MPL-1.1
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
* OF ANY KIND, either express or implied. See the LGPL or the MPL for
* the specific language governing rights and limitations.
*
* The Original Code is the cairo graphics library.
*
* The Initial Developer of the Original Code is University of Southern
* California.
*
* Contributor(s):
* Carl D. Worth <cworth@cworth.org>
* Kristian Høgsberg <krh@redhat.com>
* Chris Wilson <chris@chris-wilson.co.uk>
*/
/* Unpremultiplies data and converts native endian ARGB => RGBA bytes */
static void
unpremultiply_data (png_structp /*png*/, png_row_infop row_info, png_bytep data)
{
unsigned int i;
for (i = 0; i < row_info->rowbytes; i += 4)
{
uint8_t *b = &data[i];
uint32_t pixel;
uint8_t alpha;
memcpy (&pixel, b, sizeof (uint32_t));
alpha = (pixel & 0xff000000) >> 24;
if (alpha == 0)
{
b[0] = b[1] = b[2] = b[3] = 0;
}
else
{
b[0] = (((pixel & 0xff0000) >> 16) * 255 + alpha / 2) / alpha;
b[1] = (((pixel & 0x00ff00) >> 8) * 255 + alpha / 2) / alpha;
b[2] = (((pixel & 0x0000ff) >> 0) * 255 + alpha / 2) / alpha;
b[3] = alpha;
}
}
}
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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