Optimize script.

scripts/resize-thumbnails.sh

@@ -8,10 +8,13 @@ cd "$(dirname "$0")"
 
 cd ..
 
-rm -rf thumbnails-small
-mkdir thumbnails-small
+mkdir -p thumbnails-small
 
 cd thumbnails
 for x in *; do
-    convert $x -resize x"$thumbnail_height" ../thumbnails-small/$x
+    large=$x
+    small=../thumbnails-small/$x
+    if [ $large -nt $small ]; then
+	convert $x -resize x"$thumbnail_height" $small
+    fi
 done