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