问题描述
问题
我正在编写一个使用该标签的图标的WebExtension。我以这种方式检索当前标签页图标的URL：
var API = chrome || browser;
API.tabs.query({ active: true,currentwindow: true },function (tabs) {
if (tabs[0] && tabs[0].favIconUrl) {
console.log(tabs[0].favIconUrl);
}
});
在Firefox中，控制台记录了表示图像数据的image/x-icon数据URI，但是在Chrome中，控制台记录了指向图标位置的纯URL。例如，如果我在Firefox的stackoverflow.com中运行此命令，则会得到：
data:image/x-icon;base64,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
但是在Chrome浏览器中，我得到了：
https://cdn.sstatic.net/Sites/stackoverflow/Img/favicon.ico?v=ec617d715196
为什么这是个问题
我需要数据URI，因为我想在自己的画布上绘制收藏夹图标：
var canvas = document.createElement('canvas');
const ctx = canvas.getContext('2d');
const img = new Image();
img.crossOrigin = 'anonymous';
img.src = tabs[0].favIconUrl;
img.decode()
.then(() => {
ctx.drawImage(img,size,size);
// do other stuff on ctx ...
})
.catch(err => console.log(err));
这在Chrome中不起作用，因为网站图标URL指向其他域，因此我遇到了此错误：
Access to image at 'https://cdn.sstatic.net/Sites/stackoverflow/Img/favicon.ico?v=ec617d715196' from origin 'https://stackoverflow.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
以及图像DOMException: The source image cannot be decoded.的解码错误
我该如何解决？
Mozilla和Google都为Tab.favIconUrl列出了相同的描述，并且没有提及行为here的这种差异。我还可以如何以跨浏览器兼容的方式检索活动标签的网站图标数据URI？
解决方法
在 Chrome 中，您可以使用网站图标缓存 url chrome://favicon/https://google.com 而不是依赖 Tabs API。请参阅此示例：
Reliably getting favicons in Chrome extensions,chrome://favicon?