How can I get Blob data from image URL using javascript

Question

I have a solution but its taking too much time. Here is my solution.

//------------ Image url to base64 -------------//

    function convertImgToBase64(url, callback, outputFormat){
        var img = new Image();
        img.crossOrigin = 'Anonymous';
        img.onload = function(){
        var canvas = document.createElement('CANVAS'),
        ctx = canvas.getContext('2d'), dataURL;
        canvas.height = this.height;
        canvas.width = this.width;
        ctx.drawImage(this, 0, 0);
        dataURL = canvas.toDataURL(outputFormat);
        callback(dataURL);
        canvas = null; 
     };
       img.src = url;
    }

   //------------ convert base64 into Blob -------------//
   function dataURItoBlobImg(dataURI) {
     var byteString;
     if (dataURI.split(',')[0].indexOf('base64') >= 0)
        byteString = atob(dataURI.split(',')[1]);
     else
        byteString = unescape(dataURI.split(',')[1]);
     var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
     var ia = new Uint8Array(byteString.length);
     for (var i = 0; i < byteString.length; i++) {
         ia[i] = byteString.charCodeAt(i);
     }
     return new Blob([ia], {type:mimeString});
    }

Now thing is first I have to convert image into base64 and after that I can convert into Blob, is there is any way I can directly convert into Blob from image URL.

Thanks.

DreamTeK · Accepted Answer · 2015-10-30 09:04:34Z

Have you tried:

HTMLCanvasElement.toBlob()

The HTMLCanvasElement.toBlob() method creates a Blob object representing the image contained in the canvas; this file may be cached on the disk or stored in memory at the discretion of the user agent. If type is not specified, the image type is image/png. The created image is in a resolution of 96dpi. The third argument is used with image/jpeg images to specify the quality of the output.

Example from https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toBlob

var canvas = document.getElementById("canvas");

canvas.toBlob(function(blob) {
  var newImg = document.createElement("img"),
      url = URL.createObjectURL(blob);

  newImg.onload = function() {
    // no longer need to read the blob so it's revoked
    URL.revokeObjectURL(url);
  };

  newImg.src = url;
  document.body.appendChild(newImg);
});

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