imgdiff: A diff driver that highlights differences in images.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>

Author: Johannes Sixt

contrib/imgdiff/README

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+This directory contains facilities that allow to highlight changes
+between two images.
+
+Prerequisites
+-------------
+
+ImageMagick - http://www.imagemagick.org/script/download.php
+
+
+Installation
+------------
+
+Copy the file imgdiff into a directory that is in your PATH
+
+
+Usage
+-----
+
+Activate imgdiff in your repository
+
+a.	Define a custom diff driver:
+
+		$ git config diff.imgdiff.command imgdiff
+
+b.	Use the custom driver for your images, i.e. put
+	a line like this in your .git/info/attributes:
+
+			*.png	diff=imgdiff
+
+Since this uses ImageMagick behind the scenes, all image formats
+are supported that your ImageMagick installation supports.
+
+You can also run the program from the command line like this:
+
+	$ imgdiff pictureold.png picturenew.png

contrib/imgdiff/imgdiff

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+#!/bin/sh
+
+if test $# = 7; then
+	of="$2"
+	nf="$5"
+	echo "Image $1 changed"
+else
+	of="$1"
+	nf="$2"
+	echo "Images $of and $nf differ"
+fi
+
+d=$TMP/imgdiff$$.png
+
+trap 'rm -f "$d"' 0 1 2 15
+
+compare "$of" "$nf" "$d" &&
+imdisplay "$d"