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如何在HTML中允许跨域使用图像和画布？

HTML 图像跨域
223 2023-09-14

为了允许跨域使用图像和画布，服务器必须在其HTTP响应中包含适当的CORS（跨域资源共享）头。这些头可以设置为允许特定的来源或方法，或者允许任何来源访问资源。

HTML Canvas

An HTML5 Canvas is a rectangular area on a web page that is controlled by JavaScript code. Anything can be drawn on the canvas, including images, shapes, text, and animations. The canvas is a great tool for creating games, graphics, and web applications.

方法

允许跨域使用图像和画布的方法是将以下内容添加到标头中−

Access-Control-Allow-Origin − *

的中文翻译为：

访问控制允许来源 − *

这将允许所有的图像和画布元素在跨源时使用。

Example

的中文翻译为：

示例

下面是一个完整的工作示例，演示如何允许跨域使用图像和画布。要运行它，只需在Web浏览器中打开HTML文件。

<!DOCTYPE html>
<html>
<head>
   <script>
      function allowCrossOrigin(img, url) {
         if (url.indexOf('https://') !== 0 && url.indexOf('http://') !== 0) {
            // only allow cross-origin requests for images that are hosted on a secure
            
            // (HTTPS/HTTP) server
            return;
         }  
         // create a new Image object and set its src property to the url of the image
         
         // that we want to load
         var image = new Image();
         image.src = url;
         
         // when the image has loaded, set the src property of the img element to the
         
         // url of the image
         image.onload = function() {
            img.src = url;
         };
      }
   </script>
</head>
   <body>
      <!-- define an img element and set its src property to a local image -->
      <img id='local-image' src='https://cdn.pixabay.com/photo/2012/08/27/14/19/mountains-55067__340.png' width='200' height='200'>
      <!-- define another img element and try to set its src property to
      an image that is hosted on a different domain -->
      <img id='remote-image' width='200' height='200'>
      <script>
         // get a reference to the img element with id="remote-image"
         var remoteImage = document.getElementById('remote-image');
         
         // set the src property of the img element to the url of the image that we want
         // to load
         remoteImage.src = 'https://i.natgeofe.com/n/2a832501-483e-422f-985c-0e93757b7d84/6_square.jpg';
         
         // call the allowCrossOrigin function, passing in the img element and the url
         // of the image that we want to load
         allowCrossOrigin(remoteImage, 'https://i.natgeofe.com/n/2a832501-483e-422f-985c-0e93757b7d84/6_square.jpg');
      </script>
   </body>
</html>

来源：https://www.tutorialspoint.com/how-to-allow-cross-origin-use-of-images-and-canvas-in-html

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