painting2sprites.sh

#!/bin/bash

# painting2sprites - A simple script to read an ORA, resize and trim output PNGs.

INPUT_FILE="$1"
OUTPUT_DIR="$2"

RESIZE_SCALE="25%"

if [ "$2" == "" ]; then
    echo "Usage: $0 <input_ora> <output_dir>"
    exit 1
fi

if [ ! -r "$INPUT_FILE" ]; then
    echo "unable to open input file '$INPUT_FILE'"
    exit 2
fi

if [ ! -d "$OUTPUT_DIR" ]; then
    echo "output dir doesn't exist or is not a directory"
    exit 2
fi

# create a temporary folder
TMP_DIR=`mktemp -d` || exit 3

echo "Extracting layer data..."

# extra the contents of the ORA file
# ORA is just a ZIP, woo!
unzip -q "$INPUT_FILE" -d "$TMP_DIR"

# read layer information from the stack.xml file.
LAYER_NODES=`grep "layer" "$TMP_DIR"/stack.xml | grep -v hidden`

# go through the visible layer nodes
IFS=$'\n'
for LAYER_NODE in $LAYER_NODES; do
    # get the name and filename
    LAYER_NAME=`echo "$LAYER_NODE" | sed "s/^.*name=\"//" | sed "s/\".*$//"`
    LAYER_FILE=`echo "$LAYER_NODE" | sed "s/^.*src=\"//" | sed "s/\".*$//"`

    # skip the background layer.
    if [ "$LAYER_NAME" == "background" ]; then
        continue
    fi

    # munge the layer name into the filename.
    OUT_FILE=`echo "$LAYER_NAME" | sed "s/ /_/g" | tr "A-Z" "a-z"`

    echo "exporting layer '$LAYER_NAME' to file '${OUT_FILE}.png'"

    # auto-crop: use 'trim' to remove excess transparent border (Krita already mostly does this)
    # resize: scale down 4x to get reasonable game-sized assets.
    convert "$TMP_DIR/$LAYER_FILE" -trim -resize "$RESIZE_SCALE" "$OUTPUT_DIR/${OUT_FILE}.png"
done
unset IFS

# clean up
rm -rf "$TMP_DIR"

exit 0