app.js

var fs = require('fs'),
    util = require('util'),
    mime = require('mime'),
    path = require('path'),
    VerEx = require('verbal-expressions'),
    imagemin = require('imagemin'),
    imageminJpegRecompress = require('imagemin-jpeg-recompress'),
    imageminMozjpeg = require('imagemin-mozjpeg'),
    imageminPngquant = require('imagemin-pngquant');

function getRangeInfo (str) {

	//https://github.com/VerbalExpressions/JSVerbalExpressions/wiki
	var hasBrackets = VerEx().then('[').anything().then(']'),
		result = str.match(hasBrackets),
		range,
		zeroPadding,
		startVal,
		endVal,
		rv = null;

	if (result) {
		range = result[0].substr(1, result[0].length - 2).split('-');
		rv = {
			pattern: str.split('[' + range[0] + '-' + range[1] + ']').join('[replaceMe]'),
			zeroPadding: range[0].length,
			startValString: range[0],
			endValString: range[1],
			startVal: parseInt(range[0]),
			endVal: parseInt(range[1]),
            dirname: path.dirname(str),
            ext: path.extname(str)
		};
	}

	return rv;

}

function padDigits(number, digits) {
	return Array(Math.max(digits - String(number).length + 1, 0)).join(0) + number;
}

function base64Img(src, callback) {
    
    var useImgMin = false;

    if (useImgMin) {

        imagemin([src], null, {
            plugins: [
                imageminJpegRecompress({quality: 'medium'}) // low, medium, high and veryhigh
            ]
        }).then(function (files) {

            var data = files[0].data.toString('base64'),
                rv;

            rv = util.format('data:%s;base64,%s', mime.lookup(src), data);
            callback(rv);
        });

    } else {

        var data = fs.readFileSync(src).toString('base64');
        var rv = util.format('data:%s;base64,%s', mime.lookup(src), data);
        callback(rv);

    }

}

if(process.argv.length > 2) {

    var pathPattern = process.argv[2],
        rangeInfo = getRangeInfo(pathPattern),
        len,
        outputFile,
        framesImg = [],
        imgPath,
        b64;

    if (getRangeInfo) {

        len =  rangeInfo.endVal - rangeInfo.startVal;

        for (var i = 0; i < len + 1; i++) {
            imgPath = rangeInfo.pattern.split('[replaceMe]').join(padDigits(i, rangeInfo.zeroPadding));
            // b64 = base64Img(imgPath);
            // framesImg.push(b64);


            base64Img(imgPath, function (data) {
                framesImg.push(data);

                if (framesImg.length === len) {
                    outputFile = pathPattern.split(rangeInfo.ext).join('.seq');

                    var json = {
                        frames: framesImg
                    };

                    fs.writeFile(outputFile, JSON.stringify(json), function(err) {
                        if(err) {
                            console.log(err);
                        } else {
                            console.log('Completed!');
                        }
                    });
                }
            });
        }


    } else {
        console.error('Image path pattern unvalide, Use this form: seqs/mySequence_[00000-00002].png');
    }


} else {
    console.error('Not enough parameters supplied!');
}


/**

    Usage:
    node app.js seqs/keySeq/Volvo_Luxury_Keyfob_[00000-00015].png
    node app.js seqs/keySeq/Volvo_Luxury_Keyfob_[00000-00002].png


    node app.js seqs/keySeq/Volvo_Luxury_Keyfob_[00000-00002].jpg

**/