Photoshop JavaScript to automate exporting Android resources at multiple densities using the 3:4:6:8:12 scaling ratio.

Android Multiple Density Export.jsx

/*global alert, app, prompt, ExportOptionsSaveForWeb, ExportType, File, Folder, ResampleMethod, SaveDocumentType, SaveOptions */

///////////////////////////////////////////////////////////////////////////////
// Android Multiple Density Export.jsx
//
// Photoshop JavaScript to automate exporting Android resources at multiple
// densities using the 3:4:6:8:12 scaling ratio.
//
//
// Installation:
// 
// Place this script in your Photoshop scripts directory
// (Photoshop/Presets/Scripts). Restart Photoshop if it is open as it only 
// reads the scripts directory on start up.
//
//
// How to Use:
//
//   - Select File -> Scripts -> Android Multiple Density Export
//   - Enter the name for your resouce when prompted. (Default if the filename)
//   - Enter the source density when prompted. (Default is "xhdpi")
//   - Browse for the res directory to output the scaled resources to.
// 
// The script will export the resource once for each density. It will write
// the images to the coresponding drawable directories, creating the
// directories as needed.
//
//
// For more information on screen densities and created resouces, see:
// http://developer.android.com/guide/practices/screens_support.html
//
// Author: PJ Dietz <pj@pjdietz.com>
//
///////////////////////////////////////////////////////////////////////////////

(function () {

    "use strict";

    var doExport,
        densityTerms,
        getDensity,
        getExportDirectory,
        getResourceName,
        main;

    // Terms for the ratio 3:4:6:8:12
    densityTerms = {
        "ldpi": 3,
        "mdpi": 4,
        "hdpi": 6,
        "xhdpi": 8,
        "xxhdpi": 12
    };

    /**
     * Prompt the user for the name of the resource. 
     * @return {string}
     */
    getResourceName = function () {

        var name;

        // Start with the active document name up to the first period.
        name = app.activeDocument.name;
        name = name.substring(0, name.indexOf("."));
        return prompt("Android Resource Name", name);

    };

    /**
     * Prompt the user for the density.
     * 
     * @return {number}
     */
    getDensity = function () {

        var density;

        density = prompt("Source Image Density (ldpi, mdpi, hdpi, xhdpi, or xxhdpi", "xhdpi");

        // Ensure the user entered something.
        if (!density) {
            return;
        }

        // Translate this string into the ratio term that matches.
        density = densityTerms[density];

        if (density === undefined) {
            alert("Source density must be ldpi, mdpi, hdpi, xhdpi, or xxhdpi.");
            return getDensity();
        }

        return density;

    };

    /**
     * Prompt the user for the path to the directory to export to.
     *
     * @return Folder
     */
    getExportDirectory = function () {

        var folder;

        folder = new Folder(app.activeDocument.path);
        return folder.selectDlg("Select the directory to export to.");

    };

    /** 
     * Given a file object and factor, scale and save the image.
     *
     * @param {File} file
     * @param {number} scaleFactor
     */
    doExport = function (file, scaleFactor) {

        var copy, opts, width, height;

        // Setup the options.
        opts = new ExportOptionsSaveForWeb();
        opts.format = SaveDocumentType.PNG;
        opts.PNG8 = false;
        opts.transparency = true;

        // Duplicate the active document.
        copy = app.activeDocument.duplicate();

        // Determine the scaled size.
        width = copy.width.as("px") * scaleFactor;
        height = copy.height.as("px") * scaleFactor;
        copy.resizeImage(width, height, copy.resolution, ResampleMethod.BICUBIC);

        // Save for Web, then close without saving.
        copy.exportDocument(file, ExportType.SAVEFORWEB, opts);
        copy.close(SaveOptions.DONOTSAVECHANGES);

    };

    main = function () {

        var resourceName,
            exportDirectory,
            density,
            densityName,
            densityTerm,
            sourceDensityTerm,
            file,
            folder;

        // Prompt the user for a name for the resource.
        // By default, this will be the PSD filename, without the extension.
        resourceName = getResourceName();
        if (!resourceName) {
            return;
        }

        // Prompt the user for the density of the source image.
        sourceDensityTerm = getDensity();
        if (!sourceDensityTerm) {
            return;
        }

        // Prompt the user for the location of the Android project's res dir.
        exportDirectory = getExportDirectory();
        if (!exportDirectory) {
            return;
        }

        // Resize and save for each density.
        for (densityName in densityTerms) {
            if (densityTerms.hasOwnProperty(densityName)) {

                // Locate the corresponding drawable- directory.
                folder = new Folder(exportDirectory.absoluteURI);
                folder.changePath("./drawable-" + densityName);
                if (!folder.exists) {
                    folder.create();
                }

                // Export the resource.
                file = new File(folder.absoluteURI + "/" + resourceName + ".png");
                densityTerm = densityTerms[densityName];
                doExport(file, densityTerm / sourceDensityTerm);

            }
        }

    };

    main();

}());