如何将图像对象转换为二进制blob [英] How to convert an image object to a binary blob

问题描述

是否可以在DOM中解析一个图像对象（< img> ），就像它已经上传并用FileReader打开一样？我正尝试使用 jpegmeta.js 从JPEG中提取EXIF元数据，但它需要由FileReader返回的二进制字符串。

Is it possible to parse an image object (<img>) in the DOM as if it had been uploaded and opened with FileReader? I am trying to use jpegmeta.js to extract EXIF metadata from JPEGs, but it needs binary strings which are returned by the FileReader.

使用XHR从URL加载图像并使用FileReader解析它可能是可能的。但是，如果每个图像必须下载两次，这将产生大量开销。另一种选择可能是使用画布，但在转换时会丢失exif数据。

It might be possible to use XHR to load the image from its URL and parse it with FileReader. However, this would incur a lot of overhead if every image has to be downloaded twice. Another option could have been to use the canvas, but that loses the exif data when converting.

推荐答案

普遍的共识似乎是总结在这个答案：在JavaScript中获取图像数据？

The general consensus seems to be summed up in this answer: Get image data in JavaScript?

因此，如果您需要exif数据，则需要使用XHR技术。希望浏览器能够缓存图像，因此不会有太大的性能损失。否则画布技术应该完成这项工作。

So if you need the exif data, you'll need to use the XHR technique. Hopefully the browser will have the image cached, so it won't be too much of a performance hit. Otherwise the canvas technique should do the job.

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