问题描述

我有两个用 PNG 编码的 base64，我需要使用 比较它们Resemble.JS

I have two base64 encoded in PNG, and I need to compare them using Resemble.JS

我认为最好的方法是使用 fileReader 将 PNG 转换为文件对象.我该怎么做?

I think that the best way to do it is to convert the PNG's into file objects using fileReader. How can I do it?

推荐答案

你可以从你的base64数据创建一个Blob，然后读取它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);

完整示例(包括垃圾代码和控制台日志):http://jsfiddle.net/tTYb8/一个>

或者，您可以使用 .readAsText，它可以正常工作，而且更优雅.. 但由于某种原因 text 听起来不对 ;)

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

完整示例:http://jsfiddle.net/tTYb8/3/

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