website: add utility checks to optimize-resources.sh

docs/_scripts/optimize-resources.sh

@@ -2,12 +2,29 @@
 set -e
 cd "$(dirname "$0")/.."
 
+if ! (which svgo >/dev/null); then
+  echo 'svgo not found in $PATH (try `brew install svgo` on mac)' >&2
+  exit 1
+fi
+
+if ! (which pngcrush >/dev/null); then
+  echo 'pngcrush not found in $PATH (try `brew install pngcrush` on mac)' >&2
+  exit 1
+fi
+
+if ! (which convert >/dev/null); then
+  echo 'convert not found in $PATH (try `brew install imagemagick` on mac)' >&2
+  exit 1
+fi
+
 pushd res >/dev/null
 
+# crunch /docs/res/*.svg
 for f in *.svg; do
   svgo --multipass -q "$f" &
 done
 
+# crunch /docs/res/*.png
 for f in *.png; do
   TMPNAME=.$f.tmp
   (pngcrush -q "$f" "$TMPNAME" && mv -f "$TMPNAME" "$f") &
@@ -18,6 +35,7 @@ popd >/dev/null
 
 pushd samples/img >/dev/null
 
+# crunch /docs/samples/img/*.png
 for f in *.png; do
   TMPNAME=.$f.tmp
   if (echo "$f" | grep -q 'thumb'); then
@@ -33,11 +51,12 @@ popd >/dev/null
 
 pushd samples/icons >/dev/null
 
+# crunch /docs/samples/icons/*.svg
 for f in *.svg; do
   svgo --multipass -q "$f" &
 done
 
 popd >/dev/null
 
-
+# wait for all background processes to exit
 wait