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  3. HTML 元素参考
  4. <canvas>: The Graphics Canvas element

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使用 HTML <canvas> element 采用 画布脚本 API 或 WebGL API 绘制图形和动画。

内容类别 流内容 , 措词内容 , embedded content ，可触及内容。
准许内容 Transparent but with no interactive content descendants except for <a> elements, <button> elements, <input> elements whose type 属性为 checkbox , radio ，或 button .
Tag omission None, both the starting and ending tag are mandatory.
Permitted parents Any element that accepts 措词内容 .
Implicit ARIA role 无对应角色
Permitted ARIA roles 任何
DOM 接口 HTMLCanvasElement

属性

This element's attributes include the 全局属性 .

height

The height of the coordinate space in CSS pixels. Defaults to 150.

moz-opaque
Lets the canvas know whether or not translucency will be a factor. If the canvas knows there's no translucency, painting performance can be optimized. This is only supported by Mozilla-based browsers; use the standardized canvas.getContext('2d', { alpha: false }) 代替。
width

The width of the coordinate space in CSS pixels. Defaults to 300.

用法注意事项

Alternative content

You may (and should) provide alternate content inside the <canvas> block. That content will be rendered both on older browsers that don't support canvas and in browsers with JavaScript disabled. Providing a useful fallback text or sub DOM helps to make the the canvas more accessible .

Required </canvas> tag

不像 <img> element, the <canvas> element requires the closing tag ( </canvas> ).

Sizing the canvas using CSS versus HTML

The displayed size of the canvas can be changed using CSS, but if you do this the image is scaled during rendering to fit the styled size, which can make the final graphics rendering end up being distorted.

It is better to specify your canvas dimensions by setting the width and height attributes directly on the <canvas> elements, either directly in the HTML or by using JavaScript.

Maximum canvas size

The maximum size of a <canvas> element is very large, but the exact size depends on the browser. The following is some data we've collected from various tests and other sources (e.g. 堆栈溢出 ):

Browser Maximum height Maximum width Maximum area
Chrome 32,767 pixels 32,767 pixels 268,435,456 pixels (i.e., 16,384 x 16,384)
Firefox 32,767 pixels 32,767 pixels 472,907,776 pixels (i.e., 22,528 x 20,992)
Safari 32,767 pixels 32,767 pixels 268,435,456 pixels (i.e., 16,384 x 16,384)
IE 8,192 pixels 8,192 pixels ?

注意 : Exceeding the maximum dimensions or area renders the canvas unusable — drawing commands will not work.

范例

HTML

This code snippet adds a canvas element to your HTML document. A fallback text is provided if a browser is unable to render the canvas, or if can't read a canvas. 

<canvas width="300" height="300">
  An alternative text describing what your canvas displays.
</canvas>

JavaScript

Then in the JavaScript code, call HTMLCanvasElement.getContext() to get a drawing context and start drawing onto the canvas: 

const canvas = document.querySelector('canvas');
const ctx = canvas.getContext('2d');
ctx.fillStyle = 'green';
ctx.fillRect(10, 10, 100, 100);

结果

可访问性关注

Alternative content

<canvas> element on its own is just a bitmap and does not provide information about any drawn objects. Canvas content is not exposed to accessibility tools as semantic HTML is. In general, you should avoid using canvas in an accessible website or app. The following guides can help to make it more accessible.

规范

规范 状态 注释
HTML 实时标准
The definition of '<canvas>' in that specification. 		实时标准
HTML5
The definition of '<canvas>' in that specification. 		推荐 初始定义

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据
桌面 移动
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
canvas Chrome 完整支持 1 Edge 完整支持 12 Firefox 完整支持 1.5 注意事项
完整支持 1.5 注意事项
注意事项 Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.
注意事项 Prior to Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.
注意事项 Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead.
IE 完整支持 9 Opera 完整支持 9 Safari 完整支持 2 注意事项
完整支持 2 注意事项
注意事项 Although early versions of Apple's Safari browser don't require the closing tag, the specification indicates that it is required, so you should be sure to include it for broadest compatibility. Versions of Safari prior to version 2 will render the content of the fallback in addition to the canvas itself unless you use CSS tricks to mask it.
WebView Android 完整支持 37 Chrome Android 完整支持 18 Firefox Android 完整支持 4 注意事项
完整支持 4 注意事项
注意事项 Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.
注意事项 Prior to Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.
注意事项 Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead.
Opera Android 完整支持 10.1 Safari iOS 完整支持 1 Samsung Internet Android 完整支持 1.0
height Chrome 完整支持 1 Edge 完整支持 12 Firefox 完整支持 1.5 注意事项
完整支持 1.5 注意事项
注意事项 Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.
注意事项 Prior to Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.
注意事项 Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead.
IE 完整支持 9 Opera 完整支持 9 Safari 完整支持 2 注意事项
完整支持 2 注意事项
注意事项 Although early versions of Apple's Safari browser don't require the closing tag, the specification indicates that it is required, so you should be sure to include it for broadest compatibility. Versions of Safari prior to version 2 will render the content of the fallback in addition to the canvas itself unless you use CSS tricks to mask it.
WebView Android 完整支持 37 Chrome Android 完整支持 18 Firefox Android 完整支持 4 注意事项
完整支持 4 注意事项
注意事项 Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.
注意事项 Prior to Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.
注意事项 Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead.
Opera Android 完整支持 10.1 Safari iOS 完整支持 1 Samsung Internet Android 完整支持 1.0
moz-opaque 非标 Chrome 不支持 No Edge 不支持 No Firefox 完整支持 3.5 IE 不支持 No Opera 不支持 No Safari 不支持 No WebView Android 不支持 No Chrome Android 不支持 No Firefox Android 完整支持 4 Opera Android 不支持 No Safari iOS 不支持 No Samsung Internet Android 不支持 No
width Chrome 完整支持 1 Edge 完整支持 12 Firefox 完整支持 1.5 注意事项
完整支持 1.5 注意事项
注意事项 Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.
注意事项 Prior to Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.
注意事项 Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead.
IE 完整支持 9 Opera 完整支持 9 Safari 完整支持 2 注意事项
完整支持 2 注意事项
注意事项 Although early versions of Apple's Safari browser don't require the closing tag, the specification indicates that it is required, so you should be sure to include it for broadest compatibility. Versions of Safari prior to version 2 will render the content of the fallback in addition to the canvas itself unless you use CSS tricks to mask it.
WebView Android 完整支持 37 Chrome Android 完整支持 18 Firefox Android 完整支持 4 注意事项
完整支持 4 注意事项
注意事项 Before Firefox 5, the canvas width and height were signed integers instead of unsigned integers.
注意事项 Prior to Firefox 6, a <canvas> element with a zero width or height would be rendered as if it had default dimensions.
注意事项 Before Firefox 12, if JavaScript is disabled, the <canvas> element was being rendered instead of showing the fallback content as per the specification. Since then, the fallback content is rendered instead.
Opera Android 完整支持 10.1 Safari iOS 完整支持 1 Samsung Internet Android 完整支持 1.0

图例

完整支持

完整支持

不支持

不支持

非标。预期跨浏览器支持较差。

非标。预期跨浏览器支持较差。

见实现注意事项。

见实现注意事项。

另请参阅

元数据

  • 最后修改：
  1. <canvas>
  2. <noscript>
  3. <script>
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      2. <abbr>
      3. <acronym>
      4. <address>
      5. <applet>
      6. <area>
      7. <article>
      8. <aside>
      9. <audio>
    2. B
      1. <b>
      2. <base>
      3. <basefont>
      4. <bdi>
      5. <bdo>
      6. <bgsound>
      7. <big>
      8. <blink>
      9. <blockquote>
      10. <body>
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    3. C
      1. <canvas>
      2. <caption>
      3. <center>
      4. <cite>
      5. <code>
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    12. N
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    13. O
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    14. P
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      14. <style>
      15. <sub>
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      17. <sup>
    18. T
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      4. <template>
      5. <textarea>
      6. <tfoot>
      7. <th>
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    22. X Y Z
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