The problem is occurring because you don't save the original image. You change the image each time the slider changes, so the effect compounds. Here is what you should do instead:
In your @interface
:
@property(strong, nonatomic)UIImage *originalImage;
In your @implementation
:
-(void)viewDidLoad{
[super viewDidLoad];
self.imageView.image = self.originalImage;
}
Then when you do the effect, apply it to the originalImage
property and show the result in self.imageView.