Function twirl

pattern/canvas.js:3428–3440

(img, dx, dy, radius, angle)

}

function twirl(img, dx, dy, radius, angle) {
    /* Returns the image with a twirl distortion applied to it.
     *  - dx: horizontal offset (in pixels) of the effect.
     *  - dy: vertical offset (in pixels) of the effect.
     *  - radius: the radius of the effect in pixels.
     *  - angle: the amount of rotation in degrees.
     */
    var m1 = Math.radians(angle || 0);
    var m2 = radius || 0;
    return polar(img, dx, dy, function(d, a) { 
        return [d, a + (1 - geometry.smoothstep(-m2, m2, d)) * m1]; 
    });
}

var BUMP    = "bump";
var DENT    = "dent";