From a9c0709055d603702f6f89090e09bfb754d7e6d4 Mon Sep 17 00:00:00 2001
From: Ville Rantanen <ville.rantanen@helsinki.fi>
Date: Wed, 8 Feb 2017 15:39:32 +0200
Subject: [PATCH] iproved imgdiff

---
 files/imgdiff | 40 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/files/imgdiff b/files/imgdiff
index b2dd7c7..2d78d98 100755
--- a/files/imgdiff
+++ b/files/imgdiff
@@ -1,8 +1,40 @@
 #!/bin/bash
 
-DISP=display
-which feh &> /dev/null && DISP="feh --scale-down"
+function helpexit() {
+    echo Diff two images.
+    echo 'imgdiff "img1" "img2"'
+    echo 'If images are of different size, the 2nd image is resized to 1st size'
+    exit
+}
 
-compare -verbose -metric RMSE "$1" "$2" MIFF:- | \
-  convert -background gray -gravity center "$1" "$2" +append - -append PNG:- | $DISP -
+[[ -z "$1" ]] && helpexit
+[[ "$1" = "-h" ]] && helpexit
 
+
+DISP="display -"
+which feh &> /dev/null && DISP="feh --scale-down -"
+[[ -z "$DISPLAY" ]] && DISP="echo -n"
+
+size1=$( identify -format "%wx%h" "$1" )
+size2=$( identify -format "%wx%h" "$2" )
+
+img2="$2"
+
+if [ ! "$size1" = "$size2" ]; then
+  echo "Image sizes different. Resize introduces artefacts. $size2 -> $size1"
+  tmp2=$( mktemp --suffix .miff )
+  convert "$2" -resize "$size1"\! "$tmp2"
+  img2="$tmp2"
+  trap "rm -f \"$tmp2\"" 0 1 9 15
+fi
+diffimg=$( mktemp --suffix .miff )
+trap "rm -f \"$tmp2\"" 0 1 9 15
+convert -compose difference "$1" "$img2" -composite -auto-level -gamma 2 "$diffimg"
+
+echo -n "RMSE:" >&2
+compare -metric RMSE "$1" "$img2" MIFF:- | \
+  montage -tile 2x2 -background gray -gravity center \
+        -geometry +5+5 "$1" "$img2" \
+        - "$diffimg" PNG:- | $DISP
+echo ""
+rm -f "$diffimg"