diff --git a/engine/optim-img.sh b/engine/optim-img.sh
index 8bb2fce..6038304 100755
--- a/engine/optim-img.sh
+++ b/engine/optim-img.sh
@@ -7,13 +7,16 @@ sizeof() {
     stat --format="%s" "$*"
 }
 
-amount=0.33
-s1=$( echo "100 * $amount" | bc -l )
-s2=$( echo "100 / $amount" | bc -l )
-# convert "$src" -resize 800x800\> -scale $s1% -scale $s2% -quality 50 "$dst"
-convert "$src" -resize 800x800\> -ordered-dither o8x8,6 -colors 15 -quality 50 "$dst"
+convert "$src" -resize 800x800\> -quality 50 "$dst"
 
 before=$(sizeof $src)
 after=$(sizeof $dst)
-gain=$(( ( (before - after) * 100 ) / before ))
-print -- "$before => $after [$gain%])"
+
+if (( before <= after )); then
+  cp -f "$src" "$dst"
+  print -- "[0%] cp $before => $before"
+else
+  gain=$(( ( (before - after) * 100 ) / before ))
+  print -- "[$gain%] convert $before => $after"
+fi
+