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CanvasRenderingContext2D.createPattern() - Web API 接口参考编辑

CanvasRenderingContext2D.createPattern() 是 Canvas 2D API 使用指定的图像 (CanvasImageSource)创建模式的方法。它通过repetition参数在指定的方向上重复元图像。此方法返回一个CanvasPattern对象。

语法

CanvasPattern ctx.createPattern(image, repetition);

参数

image

作为重复图像源的 CanvasImageSource 对象。可以是下列之一：

repetition

DOMString，指定如何重复图像。允许的值有：

"repeat" (both directions),
"repeat-x" (horizontal only),
"repeat-y" (vertical only),
"no-repeat" (neither).

如果为空字符串 ('') 或 null (但不是 undefined)，repetition将被当作"repeat"。

示例

使用createPattern方法

这是一段简单的代码片段，使用 createPattern 方法创建一个指定图像和重复的CanvasPattern 对象。创建完成后，可以使用CanvasPattern.setTransform()方法对图案进行变形。如示例所示，你可以把此模式赋值给当前的fillStyle，当你使用fillRect() 方法时，会在 canvas 上绘制出效果。

HTML

<canvas id="canvas"></canvas>

JavaScript

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

var img = new Image();
img.src = 'https://www.wenjiangs.com/wp-content/uploads/2020/mozilla/Canvas_createpattern.png';
img.onload = function() {
  var pattern = ctx.createPattern(img, 'repeat');
  ctx.fillStyle = pattern;
  ctx.fillRect(0,0,400,400);
};

编辑以下代码并在线查看canvas变化：

Playable code

<canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas>
<div class="playable-buttons">
  <input id="edit" type="button" value="Edit" />
  <input id="reset" type="button" value="Reset" />
</div>
<textarea id="code" class="playable-code" style="height:120px">
var img = new Image();
img.src = 'https://www.wenjiangs.com/wp-content/uploads/2020/mozilla/Canvas_createpattern.png';
img.onload = function() {
  var pattern = ctx.createPattern(img, 'repeat');
  ctx.fillStyle = pattern;
  ctx.fillRect(0,0,400,400);
};</textarea>

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var textarea = document.getElementById("code");
var reset = document.getElementById("reset");
var edit = document.getElementById("edit");
var code = textarea.value;

function drawCanvas() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  eval(textarea.value);
}

reset.addEventListener("click", function() {
  textarea.value = code;
  drawCanvas();
});

edit.addEventListener("click", function() {
  textarea.focus();
})

textarea.addEventListener("input", drawCanvas);
window.addEventListener("load", drawCanvas);

规范描述

Specification	Status	Comment
HTML Living Standard CanvasRenderingContext2D.createPattern	Living Standard
Unknown CanvasRenderingContext2D.createPattern	Recommendation

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