How to show the effect in full screen?

To show the effect in full screen, use JavaScript fullscreen API on Canvas which renders the image.

• https://developer.mozilla.org/ru/docs/DOM/Using_fullscreen_mode
• https://developer.mozilla.org/en-US/docs/Web/API/Fullscreen_API/Guide

Or make your canvas size equal to browser window size:

canvas.width = document.body.clientWidth;
canvas.height = document.body.clientHeight;