diff --git a/retina-scale b/retina-scale
index 7405976..22658c0 100755
--- a/retina-scale
+++ b/retina-scale
@@ -12,12 +12,12 @@ def scale_retina(width, height, scale, in_file, out_dir, prefix)
   filename = "#{prefix}#{file_scale}.png"
   out_file = File.join(out_dir, filename)
   puts "> convert '#{in_file}' -scale #{width * scale}x#{height * scale} '#{out_file}'"
-  output = `convert '#{in_file}' -scale #{width * scale}x#{height * scale} '#{out_file}'`.strip
+  output = `gm convert '#{in_file}' -scale #{width * scale}x#{height * scale} '#{out_file}'`.strip
   puts output if output.length > 0
 end
 
 def image_dimensions(path)
-  `identify '#{path}'`.split[2].split('x').map(&:to_i)
+  `gm identify '#{path}'`.split[2].split('x').map(&:to_i)
 end
 
 in_file, out_dir, prefix, raw_width, raw_height = ARGV
diff --git a/scale-ios-app-icons b/scale-ios-app-icons
index 697ec95..75693d8 100755
--- a/scale-ios-app-icons
+++ b/scale-ios-app-icons
@@ -19,8 +19,9 @@ if [[ ! -d "$OUT_DIR" ]]; then
   exit 2
 fi
 
-for SIZE in 29 40 60 76 83.5; do
-  PREFIX="${IN_FILE%.png}_$SIZE"
+for SIZE in 20 29 40 60 76 83.5; do
+  FILENAME=$(basename "$IN_FILE")
+  PREFIX="${FILENAME%.png}_$SIZE"
   echo "* Generating app icons at $SIZE points with filename prefix $PREFIX"
   retina-scale "$IN_FILE" "$OUT_DIR" "$PREFIX" $SIZE $SIZE
 done