How to create inline JavaScript lazypipe function for custom file processing

gulpfile.js

var collapseSrc = function(file) {
    return lazypipe()
    .pipe(function(){
        return through.obj(function(file, enc, cb) {
            var contentTypes = {
              ".png": "image/png",
              ".gif": "image/gif",
              ".jpg": "image/jpeg",
              ".jpeg": "image/jpeg",
              ".bmp": "image/bmp",
              ".webp": "image/webp"
            };
            var base = process.cwd()+'/dist';

            if (file.isStream()) {
              console.warn('Streams not supported!');
              return cb();
            }
            if (file.isBuffer()) {
                try {
                    var dom = cheerio.load(String(file.contents));
                    var styles = [];
                    dom('img').each(function(idx, el) {
                      el = dom(el);
                      var src = el.attr('src');
                      if (src && !url.parse(src).hostname) {
                        var filepath = base + '/' + src;
                        var ext = filepath.match(/\.[a-z0-9]+$/i);
                        var img = fs.readFileSync(filepath);
                        var contentType = contentTypes[ext] || 'image/png';
                        var dataUri = "data:" + contentType + ";base64," + img.toString("base64");
                        el.attr('src', dataUri);
                      }
                    });
                    dom('source').each(function(idx, el) {
                      el = dom(el);
                      var src = el.attr('srcset');
                      if (src && !url.parse(src).hostname) {
                        var filepath = base + '/' + src.match(/^[^\s]+/i);
                        var multiplier = src.match(/[^\s]+$/i);
                        var ext = filepath.match(/\.[a-z0-9]+$/i);
                        var img = fs.readFileSync(filepath);
                        var contentType = contentTypes[ext] || 'image/png';
                        var dataUri = "data:" + contentType + ";base64," + img.toString("base64") + ' ' + multiplier;
                        el.attr('srcset', dataUri);
                      }
                    });
                    file.contents = new Buffer(dom.html({decodeEntities: false}));
                    this.push(file);
                    return cb(null, file);
                } catch(e) {
                    console.warn(e.message);
                    return cb();
                }
            }
            return cb(null, file); //no-op
        });
    })();
};