Update image generator script

Make script generate different sized versions of the original
logos ('16x16', '24x24', '32x32', '48x48', '64x64', '128x128',
'256x256' and '512x512').

scripts/generate-images.sh

@@ -0,0 +1,127 @@
+#!/usr/bin/env bash
+
+# This script automatically generates the `all-desktop.png` image as well as
+# all the different sized versions of the logos. In order for it to work, you
+# will need to have `ImageMagick Command-Line Tools` installed.
+# http://www.imagemagick.org/script/command-line-tools.php.
+
+# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+declare groupImgName="all-desktop.png"
+
+declare -a imgGroup=(
+    "../chrome/chrome.png"
+    "../firefox/firefox.png"
+    "../ie9-10/ie9-10.png"
+    "../opera/opera.png"
+    "../safari/safari.png"
+)
+
+declare -a imgSizes=(
+    '16x16'
+    '24x24'
+    '32x32'
+    '48x48'
+    '64x64'
+    '128x128'
+    '256x256'
+    '512x512'
+)
+
+# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+generate_group_img() {
+
+    # `convert` command options:
+    # http://www.imagemagick.org/script/convert.php#options
+
+    convert "${imgGroup[@]}" \
+            -background transparent \
+            -gravity center \
+            -resize 512x512 \
+            -extent 562x562 \
+            +append \
+            "../$groupImgName" \
+    && print_success_msg "  [create]" "../$groupImgName"
+}
+
+generate_imgs() {
+
+    while read i; do
+
+        # remove outdated images
+        rm ../$i/${i}_* &> /dev/null
+
+        # generate the different sized versions of an image
+        for s in ${imgSizes[@]}; do
+            convert "../$i/$i.png" \
+                    -background transparent \
+                    -gravity center \
+                    -resize "$s" \
+                    "../$i/${i}_$s.png" \
+            && print_success_msg "  [create]" "../$i/${i}_$s.png"
+        done
+
+    done < <(ls -l ../ | grep '^d' | grep -v "scripts" | cut -d":" -f2 | cut -d' ' -f2-)
+    #      └─ images directories
+
+}
+
+is_installed() {
+
+    #   0 = not installed
+    #   1 = installed
+
+    printf "$( [[ -x "$(command -v "$1")" ]] && printf "1" || printf "0" )"
+
+}
+
+print_error_msg() {
+    print_msg "$1"
+}
+
+print_msg() {
+    printf "  %s\n" "$1"
+}
+
+print_success_msg() {
+    print_msg "$1 $2"
+}
+
+# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+main() {
+
+    if [ $(is_installed "convert") -eq 1 ]; then
+
+        print_msg ""
+        print_success_msg "Generate images"
+        print_msg ""
+
+        generate_group_img \
+            && generate_imgs \
+            && (
+                print_msg ""
+                print_success_msg "Done! 🍻 "
+                print_msg ""
+            )
+
+        # Optional: start ImageOptim
+        # https://github.com/JamieMason/ImageOptim-CLI
+        if (( "$(uname -s)" == "Darwin"
+              && ( $(is_installed "imageOptim") == 1 ) )); then
+
+            print_msg ""
+            print_success_msg "Optimize images (this may take some time)"
+            print_msg ""
+
+            imageOptim --directory ../
+        fi
+
+    else
+        print_error_msg "Please install ImageMagick Command-Line Tools!"
+    fi
+
+}
+
+main