Create xcassets from three directories of PNG images - 1x, 2x and 3x

zip_directories_to_xcassets.zsh

#!/bin/zsh

# Assumes you start with three directories of images in png format with the same name - 1x, 2x and 3x
# Call with four params
# zip_directories_to_xcassets.zsh name_of_asset_file directory_of_1x_pngs directory_of_2x_pngs directory_of_3x_pngs

ASSETS_DIR=$1.xcassets
D1=$2
D2=$3
D3=$4

mkdir -p $ASSETS_DIR

cat <<EOT > $ASSETS_DIR/Contents.json
{
  "info" : {
    "author" : "xcode",
    "version" : 1
  }
}
EOT

for F in `ls $D1`; do
    ROOT_NAME=${F%%.png}
    mkdir -p $ASSETS_DIR/$ROOT_NAME.imageset
    cat <<EOT > $ASSETS_DIR/$ROOT_NAME.imageset/Contents.json
{
  "images" : [
    {
      "filename" : "$ROOT_NAME.png",
      "idiom" : "universal",
      "scale" : "1x"
    },
    {
      "filename" : "$ROOT_NAME-2.png",
      "idiom" : "universal",
      "scale" : "2x"
    },
    {
      "filename" : "$ROOT_NAME-3.png",
      "idiom" : "universal",
      "scale" : "3x"
    }
  ],
  "info" : {
    "author" : "xcode",
    "version" : 1
  }
}
EOT
  cp $D1/$ROOT_NAME.png $ASSETS_DIR/$ROOT_NAME.imageset/$ROOT_NAME.png
  cp $D2/$ROOT_NAME.png $ASSETS_DIR/$ROOT_NAME.imageset/$ROOT_NAME-2.png
  cp $D3/$ROOT_NAME.png $ASSETS_DIR/$ROOT_NAME.imageset/$ROOT_NAME-3.png
done