Often you want to batch your assets and prepare them for multiresolutions. One way great way to do it, is by using ImageMagick. It has A LOT of features to manipulate images and since it’s command line, you can just append all commands into a batch/shell script to automate it. For instance resizing all images to half just use this simple command:
/imagemagick/mogrify -resize 50% -quality 100 /images/*.png
Another awesome tool is called pngquant. Which actually reduces 24/32 bit images to 8 bit palette pngs WIDTH keeping full transparency, no idea how, but it works and is a default too to be used as best practice. Here an example for 32 colors:
/compress_pngs/pngquant --verbose --speed 1 --force --ext .png 32 /images/*.png
When it comes to handing massive collections of images for multiresolution it’s always a good idea to automate as much as possible.