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：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>CanvasGradient.addColorStop() - 使用_addcolorstop_方法 | Web176教程www.web176.com</title>
<meta name="robots" content="noindex, nofollow">
<style>
body {
padding: 0;
margin: 0;
}
svg:not(:root) {
display: block;
}
.playable-code {
background-color: #f4f7f8;
border: none;
border-left: 6px solid #558abb;
border-width: medium medium medium 6px;
color: #4d4e53;
height: 100px;
width: 90%;
padding: 10px 10px 0;
}
.playable-canvas {
border: 1px solid #4d4e53;
border-radius: 2px;
}
.playable-buttons {
text-align: right;
width: 90%;
padding: 5px 10px 5px 26px;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<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>
<script>
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);
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);
</script>
</body>
</html>作者：terry，如若转载，请注明出处：https://www.web176.com/canvas_api/7837.html
支付宝 
微信 