let width = canvas.width,height=canvas.height;
if (window.devicePixelRatio) {
canvas.style.width = width + "px";
canvas.style.height = height + "px";
canvas.height = height * window.devicePixelRatio;
canvas.width = width * window.devicePixelRatio;
ctx.scale(window.devicePixelRatio, window.devicePixelRatio);
}
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