Automatic resizing for 'non-retina' image versions

Question

I\'m looking for a solution that can save me from maintaining two versions of the same image, one for Retina displays (aka @2x), one another for non-Retina displays. My goal is

Answer 1

What I've been doing for our applications is asking our designer to export everything twice as big as it needs to be, then running a little node script to resize the images (anything named @2x in the directory where you run the script). Presently, we're just running the script when every time we deploy (it's idempotent), but it could easily be incorporated into forever -w or some other file-change-watching library like guard.

Answer 2

Old thread, but I found a use for @nschum's script - I noticed though that it doesn't round numbers for the @1x images if it's dividing an odd number. If I recall correctly this introduces a performance hit; wound up slightly revising it as below. Alters the awk call slightly to do the division there and round it accordingly, and won't re-create @1x images if one already exists (you might want to remove that, dunno).

At this point we've pretty much hit the point where non-retina isn't a big deal (the iPad 2 is all that remains...? The original Mini too, I guess), so meh. Throwing it up for posterity.

#!/bin/bash
# Downsamples all retina ...@2x.png images.

dir=$(pwd)
echo "Downsampling Retina images..."

find "$dir" -name "*@2x.png" | while read image; do
    outfile=$(dirname "$image")/$(basename "$image" @2x.png).png

    if [ "$image" -nt "$outfile" ] && [ ! -f "$outfile" ]; then
        if [[ $(dirname "$image") =~ "Images.xcassets" ]]; then
            echo "Skipping Image XCode Assets directory"
        else
            basename "$outfile"
            width=$(sips -g "pixelWidth" "$image" | awk 'FNR>1 {printf "%.0f\n", $2/2}')
            height=$(sips -g "pixelHeight" "$image" | awk 'FNR>1 {printf "%.0f\n", $2/2}')
            sips -z "$height" "$width" "$image" --out "$outfile"
            test "$outfile" -nt "$image" || exit 1
        fi
    fi
done

echo "Finished downsampling Retina images"

Answer 3

Try Resource Helper on the Mac App Store http://itunes.apple.com/us/app/resourcehelper/id521474600

It costs $10.49 but it's worth it. Checks if your images are Retina friendly (i.e. even numbered width/height dimensions) and generates the corresponding image inline. Also handles creation of ~ipad and @2x~ipad graphics as needed.

EDIT: I am not affiliated with the authors of Resource Helper.