将 base64 png 数据转换为 javascript 文件对象
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Convert base64 png data to javascript file objects
提问by Bonik
I have two base64encoded in PNG, and I need to compare them using Resemble.JS
我有两个base64PNG 编码，我需要使用Resemble.JS比较它们
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?
我认为最好的方法是PNG使用fileReader. 我该怎么做？
采纳答案by c69
You can create a Blobfrom your base64 data, and then read it asDataURL:
您可以Blob从 base64 数据创建一个，然后读取它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);
Full example (includes junk code and console log): http://jsfiddle.net/tTYb8/
完整示例（包括垃圾代码和控制台日志）：http: //jsfiddle.net/tTYb8/
Alternatively, you can use .readAsText, it works fine, and its more elegant.. but for some reason textdoes not sound right ;)
或者，您可以使用.readAsText，它工作正常，并且更优雅......但由于某种原因，文本听起来不正确;)
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
Full example: http://jsfiddle.net/tTYb8/3/
完整示例：http: //jsfiddle.net/tTYb8/3/
回答by cuixiping
Way 1: only works for dataURL, not for other types of url.
方式1：仅适用于dataURL，不适用于其他类型的url。
function dataURLtoFile(dataurl, filename) {
var arr = dataurl.split(','), mime = arr[0].match(/:(.*?);/)[1],
bstr = atob(arr[1]), n = bstr.length, u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new File([u8arr], filename, {type:mime});
}
//Usage example:
var file = dataURLtoFile('data:image/png;base64,......', 'a.png');
console.log(file);
Way 2: works for any type of url, (http url, dataURL, blobURL, etc...)
方式 2：适用于任何类型的 url，（http url、dataURL、blobURL 等...）
//return a promise that resolves with a File instance
function urltoFile(url, filename, mimeType){
mimeType = mimeType || (url.match(/^data:([^;]+);/)||'')[1];
return (fetch(url)
.then(function(res){return res.arrayBuffer();})
.then(function(buf){return new File([buf], filename, {type:mimeType});})
);
}
//Usage example:
urltoFile('data:image/png;base64,......', 'a.png')
.then(function(file){
console.log(file);
})
Both works in Chrome and Firefox.
两者都适用于 Chrome 和 Firefox。
回答by love2code
Previous answer didn't work for me.
以前的答案对我不起作用。
But this worked perfectly. Convert Data URI to File then append to FormData
但这工作得很好。 将数据 URI 转换为文件，然后附加到 FormData
