JS图片上传中file、blob、base64图片之间的相互转化

export function translate(imgData, callback) {
	var img = new Image();
	img.src = imgData.tempFilePaths[0];
	img.onload = function() {
		var that = this;
		var h = that.height; // 保证压缩后的高度一样		
		var w = that.width;  // 保证压缩后的宽度一样
		var canvas = document.createElement('canvas'); //创建canvas
		var ctx = canvas.getContext('2d'); //2d格式
		// 创建宽高属性，并给canvas新的属性节点
		var anw = document.createAttribute("width");
		anw.nodeValue = w;
		var anh = document.createAttribute("height");
		anh.nodeValue = h;
		canvas.setAttributeNode(anw);
		canvas.setAttributeNode(anh);
		ctx.drawImage(that, 0, 0, w, h); // 绘画到canvas里面		
		var quality = 0.1; //可以从 0 到 1 的区间内选择图片的质量。如果超出取值范围，将会使用默认值 0.92。其他参数会被忽略
		var base64 = canvas.toDataURL('image/jpeg', quality);//转换成base64
		canvas = null;
		var res = dataURLtoFile(base64,imgData.tempFiles[0].name);
		callback(res);
	}
} 

function base64ToFile(dataurl, filename) { //将base64转换为文件
	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});
}

function base64toBlob(dataurl) { //base64转blob
    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 Blob([u8arr], { type: mime });
}

function blobToBase64(blob, callback) { //blob转base64
    let reader = new FileReader();
    reader.onload = function (e) { callback(e.target.result); }
    reader.readAsDataURL(blob);
}

function blobToFile(blob, fileName, type) {  //blob转file
    let files = new window.File([blob], fileName, {type: type})
    return files
}

function blobToFile(blob, fileName){  // blob转file
	blob.lastModifiedDate = new Date();  
	blob.name = fileName;  
	return blob;
};

function fileToBase64（file）{   //file转bse64
	let reader = new FileReader();  
	reader.readAsDataURL(file);  
	reader.onload = function (e) {    
		return e.target.result  
	}
}