javascript - accessing cache pictures phonegap

I'm saving pictures in my application using the camera feature of Phonegap. When I try to get the file through its saved file_URI (that I got from the camera), the image doesn't load.

    function toBase64(url) {
        var canvas = document.createElement("canvas"); 
            var ctx = canvas.getContext('2d'); 
            var img = new Image();

            img.src = url; 
            if ( img.height != 0 ) {
                var height = img.height, width = img.width;
                canvas.height = height; 
                canvas.width = width; 
                ctx.drawImage(img, 0, 0, width, height);    
                try {
                    var dataURL = canvas.toDataURL("image/jpg");
                    return dataURL.replace(/^data:image\/(png|jpg);base64,/, "");    
                }

                catch (err) { console.log("ERROR " + err);}  
            }
            else {
                alert("Wrong path!");
            }
        }

The images are saved in the cache folder of the application (/data/data/my.app/cache)

Any ideas of where the problem could be from ?

Answer

I fixed this issue and had to use the FileReader object of Phonegap.

     var base64;
     function toBase64(filename) { 
        window.requestFileSystem(LocalFileSystem.TEMPORARY, 0, function(fileSystem) { 

        // Filesystem's root is the cache folder of the application: /storage/emulated/0/Android/data/com.yourcompany.whatever 
            fileSystem.root.getFile(filename, null, function(fileEntry) { 
                fileEntry.file(function(file) { 
                    var reader = new FileReader();
                    reader.onloadend = function(evt) { 
                        console.log(evt.target.result);
                        // Firing callback
                        base64 = evt.target.result;
                    };
                    reader.readAsDataURL(file);  

                }, fail);
            }, fail); 
        }, fail); 
        // We wait until the reader was fully loaded and then we return the base64 encrypted data !
        while ( base64 == "" ) {}
        base64 = base64.replace(/^data:image\/(png|jpg|jpeg);base64,/, ""); 
        return base64;
     }

Don't think that the "while(base64 == "" ) {}" is a good practice though...

EDIT: I used the do_when method of this gentleman instead of the empty loop !