Javascript - 从画布元素下的图像获取像素数据? [英] Javascript - get pixel data from image under canvas element?
问题描述
您可以使用getImageData()在画布图像上采样像素颜色数据。如果我在一个背景图片或Flash电影上层叠一个透明的canvas元素,我可以通过canvas标签来从那里抽取一个颜色吗?
You can sample pixel color data on a canvas image with getImageData(). If I layer a transparent canvas element over a background image or flash movie, can I sample a color from that via the canvas tag?
推荐答案
p> Phil的权利,你不能这样做。按照设计,Canvas只返回自己的内在像素数据,而不是任何来自其他元素的屏幕上呈现的内容。
Phil's right, you can't do it. Canvas, by design, only returns its own intrinsic pixel data, not any on-screen rendered content originating from other elements.
一个覆盖整个页面并捕获所渲染屏幕图像的canvas元素。
You could make a canvas element that covers the entire page and captures an image of the rendered screen.
如果可能, - 书写安全漏洞。您可以iframe目标网站(利用用户的Cookie /验证/内部网访问它),然后逐个像素地吸出其内容。
If possible, that would be a cross-site-scripting security hole. You could iframe a target site (leveraging the users cookies/authentication/intranet to access it), then suck out the content from it pixel by pixel.
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