在javascript中将base64转换为blob

Question

我尝试使用以下函数将JPEG的base64字符串转换为在iOS 8上运行的Cordova /混合应用程序上的blob b64toBlob.

b64toBlob = function(b64, onsuccess, onerror) {
    var img = new Image();

    img.onerror = onerror;

    img.onload = function onload() {
        var canvas = document.createElement('canvas');
        canvas.width = img.width;
        canvas.height = img.height;

        var ctx = canvas.getContext('2d');
        ctx.drawImage(img, 0, 0, canvas.width, canvas.height);

        canvas.toBlob(onsuccess);
    };

    img.src = b64;
}

但是它给出了一个错误

Uncaught Error: TypeError: undefined is not a function (evaluating 'canvas.toBlob(onsuccess)')

我们什么时候做

var imageData = "data:image/jpeg;base64," + imageData

b64toBlob(imageData,
    function(imageBlob) {
       uploadBlob(imageBlob)
    }, function(error) {
        console.log(error)
    });

如何解决这个错误？

Answer 1

试试这个功能.请注意,dataURI需要包含base64标头.(例如:"data:image/jpeg;base64,")

function b64toBlob(dataURI) {

    var byteString = atob(dataURI.split(',')[1]);
    var ab = new ArrayBuffer(byteString.length);
    var ia = new Uint8Array(ab);

    for (var i = 0; i < byteString.length; i++) {
        ia[i] = byteString.charCodeAt(i);
    }
    return new Blob([ab], { type: 'image/jpeg' });
}

用法:

...

var blob = b64toBlob(imageData);

var formData = new FormData();
formData.append("source", blob);
...

Answer 2

  fetch("data:image/jpeg;base64," + base64Data)
    .then(res => res.blob())
    .then(blob => {
      console.log(blob);
      var url = window.URL.createObjectURL(blob);
    });