error base64 image blob iphone

Hello

I have a problem in passing base64encode an image taken with the camera in iphone (I generated a text string too long)

This is the code, which according to the documentation is very simple (the same code works perfectly on android)

var myPhoto = Ti.Filesystem.getFile(Ti.Filesystem.applicationDataDirectory,'imagen.png');
            var img = myPhoto.read();
            image = Ti.Utils.base64encode(img);
            alert(myPhoto.name);
            alert(image);
            //alert(myPhoto.extension());
            myPhoto.deleteFile();

sdk titanium 3,2,2 ios 7,1