Make `<canvas>` prepared for more pixel density display.

setup-canvas.js

/**
 * Make `<canvas>` prepared for more pixel density display and returns a 2D rendering context.
 *
 * @param canvas {HTMLCanvasElement} - To be preapared.
 * @param devicePixelRatio {number} - The pixel ratio by device.
 * @returns {Canvas2DRenderingContext} - The scaled 2D rendering context.
 */
export function setupCanvas(canvas, devicePixelRatio) {
    const { width, height } = canvas;
    canvas.width *= devicePixelRatio;
    canvas.height *= devicePixelRatio;
    canvas.style.width = width + "px";
    canvas.style.height = height + "px";

    const ctx = canvas.getContext("2d");
    ctx.scale(devicePixelRatio, devicePixelRatio);
    return ctx;
}