Function add

pattern/canvas.js:3295–3297

(img1, img2, dx, dy, alpha)

}

function add(img1, img2, dx, dy, alpha) {
    return blend(ADD, img1, img2, dx, dy, alpha);
}
function subtract(img1, img2, dx, dy, alpha) {
    return blend(SUBTRACT, img1, img2, dx, dy, alpha);
}