buffer-diff.h

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

/* imagediff - Compare two images
 *
 * Copyright © 2004 Richard D. Worth
 *
 * 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 Richard Worth
 * not be used in advertising or publicity pertaining to distribution
 * of the software without specific, written prior permission.
 * Richard Worth makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 *
 * RICHARD WORTH DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN
 * NO EVENT SHALL RICHARD WORTH 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: Richard D. Worth <[e-mail]> */

#ifndef BUFFER_DIFF_H
#define BUFFER_DIFF_H

/* Returns number of pixels changed.
 * Also fills in a "diff" buffer intended to visually show where the
 * images differ.
 */
int
buffer_diff (unsigned char *buf_a,
	     unsigned char *buf_b,
	     unsigned char *buf_diff,
	     int	    width,
	     int	    height,
	     int	    stride_a,
	     int	    stride_b,
	     int	    stride_diff);

/* Returns number of pixels changed ignoring the alpha channel.
 * Also fills in a "diff" buffer intended to visually show where the
 * images differ.
 */
int
buffer_diff_noalpha (unsigned char *buf_a,
		     unsigned char *buf_b,
		     unsigned char *buf_diff,
		     int	    width,
		     int	    height,
		     int	    stride_a,
		     int	    stride_b,
		     int	    stride_diff);

/* Returns number of pixels changed, (or -1 on error).
 * Also saves a "diff" image intended to visually show where the
 * images differ.
 */
int
image_diff (const char *filename_a,
	    const char *filename_b,
	    const char *filename_diff,
	    int		ax,
	    int		ay,
	    int		bx,
	    int		by);

/* Like image_diff, but blending the contents of b over white first. */
int
image_diff_flattened (const char *filename_a,
		      const char *filename_b,
		      const char *filename_diff,
                      int         ax,
                      int         ay,
                      int         bx,
                      int         by);

#endif