index.js

var es = require('event-stream');
var path = require('path');
var fs = require('fs');
var gutil = require('gulp-util');
var mime = require('mime');

module.exports = function(opts) {

    opts = opts ||  {};

    if (!opts.baseDir) opts.baseDir = path.dirname(module.parent.filename);

    var datauri = function(file, callback) {
        var app_path = opts.baseDir;
        var reg_exp = /url\([ '"]?(.*?)[ '"]?(|\,(.*?))\)/g;
        var isStream = file.contents && typeof file.contents.on === 'function' && typeof file.contents.pipe === 'function';
        var isBuffer = file.contents instanceof Buffer;
        if(opts.useRelativePath){
            app_path = file.path.replace(/\/[^/]+$/, '/');
        }
        if (isBuffer) {
            var str = String(file.contents);

            var matches = [],
                found,
                force;
            while (found = reg_exp.exec(str)) {
                matches.push({
                    'txt': found[0],
                    'url': found[1],
                    'force': found[2].replace(/(\,|\ )/g, '') == 'true' ? true : false
                });
            }

            for (var i = 0, len = matches.length; i < len; i++) {
                if (matches[i].url.indexOf('data:image') === -1) { //if find -> image already decoded
                    var filepath = app_path + path.normalize(matches[i].url);
                    if (fs.existsSync(filepath)) {
                        var size = fs.statSync(filepath).size;

                        // File will not be included because of its size
                        if (opts.maxSize && size > opts.maxSize && !matches[i].force) {
                            if (opts.debug) gutil.log('gulp-inline-base64:', gutil.colors.yellow('file is greater than ' + Math.round(size / 1024) + 'kb > ' + Math.round(opts.maxSize / 1024) + 'kb => skip') + gutil.colors.gray(' (' + filepath + ')'));
                            str = str.replace(matches[i].txt, 'url(' + matches[i].url + ')');
                        }

                        // Else replace by inline base64 version
                        else {
                            var b = fs.readFileSync(filepath);
                            str = str.replace(matches[i].txt, 'url(' + ('data:' + mime.getType(filepath) + ';base64,' + b.toString('base64')) + ')');
                        }

                    } else {
                        if (opts.debug) gutil.log('gulp-inline-base64:', gutil.colors.red('file not found => skip') + gutil.colors.gray(' (' + filepath + ')'));
                    }
                }
            }
            file.contents = new Buffer(str);

            return callback(null, file);
        }

        callback(null, file);
    };

    return es.map(datauri);
};