CanvasRenderingContext2D.shadowBlur 是 Canvas 2D API 描述模糊效果程度的属性； 它既不对应像素值也不受当前转换矩阵的影响。 默认值是 0。
语法
ctx.shadowBlur = level;
示例
使用 shadowBlur 属性
这是一段简单的代码片段，使用 shadowblur 属性设置模糊阴影。 注意：只有设置shadowColor属性值为不透明，阴影才会被绘制。
HTML
<canvas id="canvas"></canvas>
JavaScript
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
ctx.shadowColor = "black";
ctx.shadowBlur = 10;
ctx.fillStyle = "white";
ctx.fillRect(10, 10, 100, 100);
修改下面的代码并在线查看 canvas 的变化：
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"> ctx.shadowColor = "black"; ctx.shadowBlur = 10; ctx.fillStyle = "white"; ctx.fillRect(10, 10, 100, 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);
规范描述
| Specification | Status | Comment |
|---|---|---|
| HTML Living Standard CanvasRenderingContext2D.shadowBlur |
Living Standard |
浏览器兼容性
We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
| Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
WebKit/Blink-specific 注解
- 在基于 WebKit- 和 Blink- 的浏览器中，除了此属性外，还实现了一个不规范的并且不赞成使用的方法
ctx.setShadow()。setShadow(width, height, blur, color, alpha); setShadow(width, height, blur, graylevel, alpha); setShadow(width, height, blur, r, g, b, a); setShadow(width, height, blur, c, m, y, k, a);
参见
- 接口定义，
CanvasRenderingContext2D.