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CanvasGradient.addColorStop() - Web API 接口参考编辑

CanvasGradient.addColorStop() 方法添加一个由偏移值和颜色值指定的断点到渐变。如果偏移值不在0到1之间，将抛出INDEX_SIZE_ERR错误，如果颜色值不能被解析为有效的CSS颜色值 <color>，将抛出SYNTAX_ERR错误。

语法

void gradient.addColorStop(offset, color);

参数

offset: 0到1之间的值，超出范围将抛出INDEX_SIZE_ERR错误
color: CSS颜色值 <color>。如果颜色值不能被解析为有效的CSS颜色值 <color>，将抛出SYNTAX_ERR错误。

示例

使用addColorStop方法

一个使用CanvasGradient对象的addColorStop 方法的简单例子

HTML

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

JavaScript

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

var gradient = ctx.createLinearGradient(0,0,200,0);
gradient.addColorStop(0,"green");
gradient.addColorStop(1,"white");
ctx.fillStyle = gradient;
ctx.fillRect(10,10,200,100);

编辑以下代码可看到画布变化:

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">
var gradient = ctx.createLinearGradient(0,0,200,0);
gradient.addColorStop(0,"green");
gradient.addColorStop(1,"white");
ctx.fillStyle = gradient;
ctx.fillRect(10,10,200,100);</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);

标准

标准	状态	备注
HTML Living Standard CanvasGradient.addColorStop	Living Standard
Unknown CanvasGradient.addColorStop	Recommendation

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