static getSubimage(srcImage, x0, y0, w, h) {
        let canvas = document.createElement('canvas');

        canvas.width = srcImage.width;
        canvas.height = srcImage.height;
        let ctx = canvas.getContext('2d');
        ctx.putImageData(srcImage, 0, 0);
        let subimage = ctx.getImageData(x0, y0, w, h);
        console.debug("getSubimage --> done");
        canvas.remove();
        console.log(subimage);
        return subimage;
    }