canvasエレメントはwidthとstyle.widthを別個に持つ

Note further that the height and width are the logical canvas dimensions used for drawing and are different from the style.height and style.width CSS attributes.

code::

// Make a canvas that has a blurry pixelated zoom-in

// with each canvas pixel drawn showing as roughly 2x2 on screen

canvas.width = 400;

canvas.height = 300;

canvas.style.width = '800px';

canvas.style.height = '600px';