Attempts to list all the images that are not referenced in your html and css.

Images are match by filename only. This is because its likely that the 'filesystem' that a browser will see is very different from the one that gulp sees.

Images with absolute urls will also be ignored.

Stream all the images, css and html files that you have into it, it emits errors, so use plumber to catch and see them

gulp.task('images:filter', function () {
    return gulp.src(['app/images/**/*', '.tmp/styles/**/*.css', 'app/*.html', 'app/partials/**/*.html'])
        .pipe(plumber())
        .pipe(unusedImages())
        .pipe(plumber.stop());
});

• Type: Boolean
• Default: true

Whether to emit errors for unused images

The output lists the images that it found no references to and any ng-src attributes that it saw, allowing you to try and decided what that would refer to

Error: Unused images: arrow_grey_right.png, bg-circel-not-empty-small.png
ng-src: {{ app.iconUrl || 'images/generic_android_icon.png' }}