canvas = {
const width = 256, height = 256;
const edgeWidth = 30;
var canvas = document.createElement('canvas');
canvas.width = width;
canvas.height = height;
var context = canvas.getContext('2d');
context.fillStyle = 'black';
context.fillRect(0, 0, width, height);
context.fillStyle = 'white';
context.fillRect(edgeWidth, 0, width - edgeWidth * 2, height);
return canvas;
}