/* 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: */