gulp-images

var gulp = require('gulp'), images = require('./app.js');
 
 
gulp.task('default', function(){
    return gulp.src('images/*').pipe(images()).pipe(gulp.dest('build'));
});

File image.png The file can be any supported by gm

File image.png.json, need to be within the image.

If you want to apply any of the gm functions, just set a string or an array for more than two arguments. For example for gm("img.png").gaussian(radius [,sigma]) use gaussian: radius or gaussian: [radius, sigma]

{
    "@2x": {
        "size": "200",
        "fixDensity": true,
        "format": "png",
        "gaussian": [5, 5]
    },
    "@1x": {
        "format": "png",
        "size": "100"
    },
    "-favicon": {
        "size": "30x30",
        "format": "ico"
    }
}