Image cannot be saved using UIImageWriteToSavedPhotosAlbum to photo album - objective-c

Question

I have a save button called save to photo album. On top of the button is the small UIImageView where user can click the button below to save the actual size of the photo to photo album. My problem is that when I click the save button, it shows an error : Unable to save image to Photo Album.
I think I have done it right but my experience is too limited.
H file:
#import <UIKit/UIKit.h>
#interface SecondViewController : UIViewController {
IBOutlet UIButton *btnReturn;
IBOutlet UIButton *savePhoto;
IBOutlet UIImage *saveImage;
}
#property (nonatomic, retain) IBOutlet UIButton *btnReturn;
#property (nonatomic, retain) IBOutlet UIButton *savePhoto;
#property (nonatomic, retain) IBOutlet UIImage *saveImage;
-(IBAction) saveToPhotoAlbum;
#end
Below is my code:
-(IBAction) saveToPhotoAlbum{
NSString *saveMyPhoto=[NSHomeDirectory() stringByAppendingPathComponent:#"sample.png"];
UIImage *saved=[UIImage imageWithContentsOfFile:saveMyPhoto];
NSData *imageData = [NSData dataWithContentsOfFile:(NSString *)UIImagePNGRepresentation(saved)];
[imageData writeToFile:(NSString *)saved atomically:YES ];
UIImageWriteToSavedPhotosAlbum(saved, self, #selector(image:didFinishSavingWithError:contextInfo:), nil);
}
- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
UIAlertView *alert;
if (error)
alert = [[UIAlertView alloc] initWithTitle:#"Error"
message:#"Unable to save image to Photo Album."
delegate:self cancelButtonTitle:#"Ok"
otherButtonTitles:nil];
else
alert = [[UIAlertView alloc] initWithTitle:#"Success"
message:#"Image saved to Photo Album."
delegate:self cancelButtonTitle:#"Ok"
otherButtonTitles:nil];
[alert show];
[alert release];
}

Answer 1

Just create a UIImage object and load the image from file. Then just call the UIIMageWriteToSavedPhotoAlbum function and pass the UIImage object as the first parameter and then the rest could all be NIL. See the Apple SDK documentation.

Answer 2

These lines look really really suspect :
NSString *saveMyPhoto=[NSHomeDirectory() stringByAppendingPathComponent:#"sample.png"];
...
UIImage *saved = [UIImage imageWithContentsOfFile:saveMyPhoto];
...
[imageData writeToFile:(NSString *)saved atomically:YES ];
What are you expecting this to do? You get a path to an image, load it and then save it again but you've cast a UIImage to an NSString and are hoping it will magically turn into a valid path on the disk?
As for the question you're asking, are you sure that your image is a valid image?