I want to implement vertical scrolling of the contents of a HTML5 canvas element. I don't want to render the whole content again. Instead I would like to move the whole content down/up and only render the area, which has been scrolled into view.
I experimented with the
// scroll 20px down
var data = ctx.getImageData(0, 0, width, height-20);
ctx.drawImage(ctx.canvas, 0, 0, width, height-20, 0, 20, width, height-20);
drawImage can take either an
HTMLCanvasElement, or an
HTMLVideoElement for the first argument.