javascript - Canvas 在边缘上 Blob

Question

尝试将 Html canvas 元素转换为 blob 时，Microsoft Edge 浏览器出现异常。一切都在普通浏览器上运行良好。异常:

SCRIPT438: Object doesn't support property or method 'toBlob'

HTML 片段:

<canvas id="cnv" width="640px" height="520px" style="display: none"></canvas>

Javascript:

var files[];
var canvas = document.getElementById('cnv');
canvas.toBlob(function (blob) {            
        files.push(blob);
         }
    }, 'image/jpeg', 1);

当我调用 toBlob 方法时，我得到了这个异常。有什么方法可以教 Edge blob 转换吗？我正在使用:

Microsoft Edge 41.16299.15.0

Answer 1

这个小 polyfill 取自 from here一定要帮忙see jsfiddle

if (!HTMLCanvasElement.prototype.toBlob) {
   Object.defineProperty(HTMLCanvasElement.prototype, 'toBlob', {
     value: function (callback, type, quality) {
       var canvas = this;
       setTimeout(function() {
         var binStr = atob( canvas.toDataURL(type, quality).split(',')[1] ),
         len = binStr.length,
         arr = new Uint8Array(len);

         for (var i = 0; i < len; i++ ) {
            arr[i] = binStr.charCodeAt(i);
         }

         callback( new Blob( [arr], {type: type || 'image/png'} ) );
       });
     }
  });
}

这也有帮助 github.com/blueimp/JavaScript-Canvas-to-Blob