base64转换PNG数据的JavaScript文件对象 [英] Convert base64 png data to javascript file objects

问题描述

我有两个连接的base64 codeD PNG的，我要使用这个库对它们进行比较：
https://github.com/Huddle/Resemble.js

I have two base64 encoded png's, and i want to compare them using this library: https://github.com/Huddle/Resemble.js

我认为要做到这一点的最好办法是转换PNG的成文件对象使用的FileReader，
但我无法弄清楚如何这样：（

i think that the best way to do it is to convert the png's into file objects using fileReader, but i can't figure out how to to this :(

什么想法？

感谢您！

推荐答案

您可以创建一个的Blob 从您的base64数据，然后读 asDataURL ：

You can create a Blob from your base64 data, and then read it asDataURL:

var img_b64 = canvas.toDataURL('image/png');
var png = img_b64.split(',')[1];

var the_file = new Blob([window.atob(png)],  {type: 'image/png', encoding: 'utf-8'});

var fr = new FileReader();
fr.onload = function ( oFREvent ) {
    var v = oFREvent.target.result.split(',')[1]; // encoding is messed up here, so we fix it
    v = atob(v);
    var good_b64 = btoa(decodeURIComponent(escape(v)));
    document.getElementById("uploadPreview").src = "data:image/png;base64," + good_b64;
};
fr.readAsDataURL(the_file);

完整的示例（包括垃圾code和控制台日志的）： http://jsfiddle.net/tTYb8 /

另外，你可以使用 .readAsText ，它工作正常，而其更优雅..但由于某些原因的文本的不健全的权利;）

Alternatively, you can use .readAsText, it works fine, and its more elegant.. but for some reason text does not sound right ;)

fr.onload = function ( oFREvent ) {
    document.getElementById("uploadPreview").src = "data:image/png;base64,"
    + btoa(oFREvent.target.result);
};
fr.readAsText(the_file, "utf-8"); // its important to specify encoding here

完整的示例： http://jsfiddle.net/tTYb8/3/

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