How to use canvas.toDataURL() to get base64 of image in Adobe AIR?

air, base64, html5-canvas, javascript

Solution

Adobe AIR enforces same origin for images used in the canvas API. Once you've used something from another domain in your canvas, you can't get pixel data back out of it. However, you can make use of the Loader class to get the pixel data, and convert it into a canvas ImageData.

For example:

function getDataURL(url, callback) {
  var loader = new air.Loader();
  loader.contentLoaderInfo.addEventListener(air.Event.COMPLETE, function(event) {
    var bitmapData = loader.content.bitmapData;

    var canvas = document.createElement('canvas');
    canvas.width = bitmapData.width;
    canvas.height = bitmapData.height;
    var context = canvas.getContext('2d');
    var imageData = context.createImageData(canvas.width, canvas.height);

    var dst = imageData.data;
    var src = bitmapData.getPixels(bitmapData.rect);
    src.position = 0;

    var i = 0;
    while (i < dst.length) {
      var alpha = src.readUnsignedByte();
      dst[i++] = src.readUnsignedByte();
      dst[i++] = src.readUnsignedByte();
      dst[i++] = src.readUnsignedByte();
      dst[i++] = alpha;
    }

    context.putImageData(imageData, 0, 0);
    callback(canvas.toDataURL());
  });
  loader.load(new air.URLRequest(url));
}

window.addEventListener('load', function() {
  getDataURL('http://www.google.com/images/logo.gif', function(dataURL) {
    air.trace(dataURL);
  });
}, false);

Problem

Original source