Crop Image

/**
 * cropW, cropH: width and height to be cropped
 * w, h: width and height of source image
 */
function crop(cropW, cropH, w, h) {
    let k1 = cropW / w;
    let k2 = cropH / h;
    let k = k1 > k2 ? k1 : k2;
    let fitW = Math.ceil(w * k);
    let fitH = Math.ceil(h * k);
    let topLeftX = Math.ceil((fitW - cropW) / 2);
    let topLeftY = Math.ceil((fitH - cropH) / 2);
    
    console.info('fit wxh:' + fitW + 'x' + fitH + ' crop from (' + topLeftX + ',' + topLeftY + ')');
}