转 Blob、DataURL、canvas、image的相互转换

https://blog.csdn.net/weixin_38659265/article/details/105412432

最近开发过程中碰到的问题：

接收到的是Blob对象，需要转换成img可以使用的src，用到的是如下方法，但是window.URL.createObjectURL不兼容IE9，在解决这个问题的时候，想着看是否可以换种方式考虑：

var url = window.URL.createObjectURL(blob);
document.getElementById("validCode").src = url;
Blob/DataURL/canvas/image的相互转换
/*-----------------------------------------------------------------------*/
// canvas转dataURL：canvas对象、转换格式、图像品质
function canvasToDataURL(canvas, format, quality){
return canvas.toDataURL(format||'image/jpeg', quality||1.0);
}
// DataURL转canvas
function dataURLToCanvas(dataurl, cb){
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var img = new Image();
img.onload = function(){
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
cb(canvas);
};
img.src = dataurl;
}
/*-----------------------------------------------------------------------*/
// image转canvas：图片地址
function imageToCanvas(src, cb){
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var img = new Image();
img.src = src;
img.onload = function (){
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
cb(canvas);
};
}
// canvas转image
function canvasToImage(canvas){
var img = new Image();
img.src = canvas.toDataURL('image/jpeg', 1.0);
return img;
}
/*-----------------------------------------------------------------------*/
// File/Blob对象转DataURL
function fileOrBlobToDataURL(obj, cb){
var a = new FileReader();
a.readAsDataURL(obj);
a.onload = function (e){
cb(e.target.result);
};
}
// DataURL转Blob对象
function dataURLToBlob(dataurl){
var arr = dataurl.split(',');
var mime = arr[0].match(/:(.*?);/)[1];
var bstr = atob(arr[1]);
var n = bstr.length;
var u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new Blob([u8arr], {type:mime});
}
/*-----------------------------------------------------------------------*/
// Blob转image
function blobToImage(blob, cb){
fileOrBlobToDataURL(blob, function (dataurl){
var img = new Image();
img.src = dataurl;
cb(img);
});
}
// image转Blob
function imageToBlob(src, cb){
imageToCanvas(src, function (canvas){
cb(dataURLToBlob(canvasToDataURL(canvas)));
});
}
/*-----------------------------------------------------------------------*/
// Blob转canvas
function BlobToCanvas(blob, cb){
fileOrBlobToDataURL(blob, function (dataurl){
dataURLToCanvas(dataurl, cb);
});
}
// canvas转Blob
function canvasToBlob(canvas, cb){
cb(dataURLToBlob(canvasToDataURL(canvas)));
}
/*-----------------------------------------------------------------------*/
// image转dataURL
function imageToDataURL(src, cb){
imageToCanvas(src, function (canvas){
cb(canvasToDataURL(canvas));
});
}
// dataURL转image，直接赋值给img的src
function dataURLToImage(dataurl){
var img = new Image();
img.src = dataurl;
return img;
}

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原文链接：https://blog.csdn.net/weixin_38659265/article/details/105412432