img标签如何通过cors标头获取内容 [英] How img tag gets content over cors headers

问题描述

为什么当我使用fetch来从具有禁用的CORS响应头的服务器上加载数据时，预计会出现错误：

无法加载http：/ /www.imgworlds.com/wp-content/uploads/2015/12/18-CONTACTUS-HEADER.jpg：所请求的资源上没有 Access-Control-Allow-Origin标头。因此，不允许访问来源 http：// localhost：63343。如果不透明的响应满足您的需求，请将请求的模式设置为 no-cors，以在禁用CORS的情况下获取资源。

但是显示了img标签中的图像

Why, when I use fetch, to load the data from the server with disabled response CORS headers, I'v expectedly got an error:
Failed to load http://www.imgworlds.com/wp-content/uploads/2015/12/18-CONTACTUS-HEADER.jpg: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:63343' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
But image from img tag is presented

<script>
    fetch('http://www.imgworlds.com/wp-content/uploads/2015/12/18-CONTACTUS-HEADER.jpg').then(console.log);
</script>
<img src="http://www.imgworlds.com/wp-content/uploads/2015/12/18-CONTACTUS-HEADER.jpg">

推荐答案

跨域共享标准不包括 img 标记，但是XHR / fetch请求以及某些情况（包括将图像绘制到画布）确实可以。

The cross-origin sharing standard does not include img tags, but XHR/fetch requests and some cases including drawing images to a canvas does.

有关更多信息：
https://developer.mozilla.org/zh-CN/docs/Web/HTTP/CORS#What_requests_use_CORS

这篇关于img标签如何通过cors标头获取内容的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！