CanvasRenderingContext2D：createPattern() 方法

createPattern(image, repetition)

<canvas id="canvas" width="300" height="300"></canvas>

const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");

const img = new Image();
img.src = "canvas_createpattern.png";
// Only use the image after it's loaded
img.onload = () => {
  const pattern = ctx.createPattern(img, "repeat");
  ctx.fillStyle = pattern;
  ctx.fillRect(0, 0, 300, 300);
};

// Create a pattern, offscreen
const patternCanvas = document.createElement("canvas");
const patternContext = patternCanvas.getContext("2d");

// Give the pattern a width and height of 50
patternCanvas.width = 50;
patternCanvas.height = 50;

// Give the pattern a background color and draw an arc
patternContext.fillStyle = "#fec";
patternContext.fillRect(0, 0, patternCanvas.width, patternCanvas.height);
patternContext.arc(0, 0, 50, 0, 0.5 * Math.PI);
patternContext.stroke();

// Create our primary canvas and fill it with the pattern
const canvas = document.createElement("canvas");
const ctx = canvas.getContext("2d");
const pattern = ctx.createPattern(patternCanvas, "repeat");
ctx.fillStyle = pattern;
ctx.fillRect(0, 0, canvas.width, canvas.height);

// Add our primary canvas to the webpage
document.body.appendChild(canvas);