nodejs + gearman + gm + pngquant + pngcrush thumbnail generator

thumbnail.js

#!/usr/bin/env node

var path = require('path'),
    exec = require('child_process').exec,
    when = require('when'),
    gm = require('gm'),
    Gearman = require('node-gearman'),
    gearman = new Gearman(),
    options = {
        thumbDir: path.join(__dirname, 'thumb'),
        uploadDir: path.join(__dirname, 'files'),
        outputFormat: 'png'
    },
    thumbnail = function(inputFile, outputFile) {
        var deferred = when.defer();
        gm(inputFile).setFormat(options.outputFormat)
                     .quality(90)
                     .filter('Lanczos')
                     .gravity('Center')
                     .resize(100, 100, '>')
                     .sharpen(0, 0.3)
                     .background('transparent')
                     .extent(100, 100)
                     .write(outputFile,
        function(err) {
            if (err) {
                deferred.reject(err);
            } else {
                console.log('thumbnail: done!');
                deferred.resolve(outputFile);
            }
        });
        return deferred.promise;
    },
    pngquant = function(inputFilePromise) {
        var deferred = when.defer();
        when(inputFilePromise, function(inputFile) {
            exec('pngquant -f --ext .png ' + inputFile, {timeout: 60000}, function(err, stdout, stderr) {
                if (err) {
                    deferred.reject(err);
                } else {
                    console.log('pngquant: done!');
                    deferred.resolve(inputFile);
                }
            });
        });
        return deferred.promise;
    },
    pngcrush = function(inputFilePromise) {
        var deferred = when.defer();
        when(inputFilePromise, function(inputFile) {
            exec('pngcrush -ow ' + inputFile, {timeout: 60000}, function(err, stdout, stderr) {
                if (err) {
                    deferred.reject(err);
                } else {
                    console.log('pngcrush: done!');
                    deferred.resolve(inputFile);
                }
            });
        });
        return deferred.promise;
    };

gearman.registerWorker('resize', function(payload, worker) {
    if (!payload) {
        console.log('Invalid job');
        worker.error();
        return;
    }
    var filename = payload.toString('utf-8'),
        inputfile = path.join(options.uploadDir, filename),
        outputfile = path.join(
            options.thumbDir,
            path.basename(filename, path.extname(filename)) + '.' + options.outputFormat
        ),
        errorHandler = function(err) {
            console.log('Error: ' + err);
            worker.error();
        };

    console.log('thumbnail: ' + inputfile);
    worker.write('thumbnail');
    try {
        when(thumbnail(inputfile, outputfile),
            function(file) {
                console.log('pngquant: ' + file);
                worker.write('pngquant');
                return pngquant(file);
            }, errorHandler
        ).then(
            function(file) {
                console.log('pngcrush: ' + file);
                worker.write('pngcrush');
                return pngcrush(file);
            }, errorHandler
        ).then(
            function(file) {
                console.log('success: ' + file);
                worker.end(file);
            }, errorHandler
        );
    }
    catch(err) {
        errorHandler(err);
        return;
    }
});