我可以获取从URL加载的图像的Blob数据吗？

Question

I'm wondering if it's possible to get the blob data (like base64 encoded or something) of an image that's already loaded, via javascript?

The use case would be that I get a captcha image from a webpage into an android app.

Answer 1

You may be able to use getImageData from the Canvas API. See https://developer.mozilla.org/En/HTML/Canvas/Pixel_manipulation_with_canvas for example. So you can create a canvas, render the image onto it, and then use getImageData on the canvas to get the pixels.

One obstacle to this, though, is the same origin policy. If the image that you're parsing comes from the same domain as your JavaScript, I think you're fine, but if the image comes from an external source, getImageData is going to fail due to the same origin policy.