HTML5 Canvas drawImage ratio bug iOS

I want to resize the image taken from the iOS camera on the client side with HTML5 Canvas but I keep running in this weird bug where the image has a wrong ratio if bigger than ~1.5mb

It works on the desktop but not in the latest iOS version with the media upload API.

You can see an example here: http://jsbin.com/ekuros/1

Any idea how to fix this please? Is this a memory issue?

$('#file').on('change', function (e) {
    var file = e.currentTarget.files[0];
    var reader = new FileReader();
    reader.onload = function (e) {
        var image = $('<img/>');
        image.on('load', function () {
            var square = 320;
            var canvas = document.createElement('canvas');

            canvas.width = square;
            canvas.height = square;

            var context = canvas.getContext('2d');
            context.clearRect(0, 0, square, square);
            var imageWidth;
            var imageHeight;
            var offsetX = 0;
            var offsetY = 0;

            if (this.width > this.height) {
                imageWidth = Math.round(square * this.width / this.height);
                imageHeight = square;
                offsetX = - Math.round((imageWidth - square) / 2);
            } else {
                imageHeight = Math.round(square * this.height / this.width);
                imageWidth = square;    
                offsetY = - Math.round((imageHeight - square) / 2);            
            }

            context.drawImage(this, offsetX, offsetY, imageWidth, imageHeight);
            var data = canvas.toDataURL('image/jpeg');

            var thumb = $('<img/>');
            thumb.attr('src', data);
            $('body').append(thumb);
        });
        image.attr('src', e.target.result);
    };
    reader.readAsDataURL(file);
});