Objective C - Saving a Filtered UIImage - objective-c

Question

I have a view with a slider and a background image. The background image is updated according to the slider, where the slider controls the level of the filter.
I am using this framework https://github.com/BradLarson/GPUImage to process the image with the filter.
From the code below, the image is updating with the slider, and the filter is working great. However I am trying to save the image once processed by the filter(to set a UIImage in another class), but I cannot achieve this(the filtered image is not saved, but the ufiltered image is saved)... am I saving the image wrong, incorrect format?
Please help me I have been at this for hours!
- (void)loadView
{
CGRect mainScreenFrame = [[UIScreen mainScreen] applicationFrame];
GPUImageView *primaryView = [[GPUImageView alloc] initWithFrame:mainScreenFrame];
self.view = primaryView;
*imageSlider = [[UISlider alloc] initWithFrame:CGRectMake(25.0, mainScreenFrame.size.height - 50.0, mainScreenFrame.size.width - 50.0, 40.0)];
[imageSlider addTarget:self action:#selector(updateSliderValue:) forControlEvents:UIControlEventValueChanged];
imageSlider.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin;
imageSlider.minimumValue = 0.0;
imageSlider.maximumValue = 1.0;
imageSlider.value = 0.5;
[primaryView addSubview:imageSlider];
[self setupDisplayFiltering];
- (IBAction)updateSliderValue:(id)sender
{
CGFloat midpoint = [(UISlider *)sender value];
[(GPUImageBrightnessFilter *)sepiaFilter setBrightness:midpoint];
//[(GPUImageSepiaFilter *)sepiaFilter setIntensity:[(UISlider *)sender value]];
//[(GPUImageSaturationFilter *)sepiaFilter setSaturation:midpoint];
//[(GPUImageRGBFilter *)sepiaFilter setGreen:midpoint];
[sourcePicture processImage];
}
- (void)setupDisplayFiltering;
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *imageToUseData = [defaults dataForKey:#"imageToUse"];
UIImage *inputImage = [UIImage imageWithData:imageToUseData];
sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage smoothlyScaleOutput:YES];
//sepiaFilter = [[GPUImageSepiaFilter alloc] init];
sepiaFilter = [[GPUImageBrightnessFilter alloc] init];
GPUImageView *imageView = (GPUImageView *)self.view;
[sepiaFilter forceProcessingAtSize:imageView.sizeInPixels]; // This is now needed to make the filter run at the smaller output size
[sourcePicture addTarget:sepiaFilter];
[sepiaFilter addTarget:imageView];
[sourcePicture processImage];
UIImage *outputImage = [sepiaFilter imageFromCurrentlyProcessedOutput];
UIImage *quickFilteredImage = [brightnessFilter imageByFilteringImage:inputImage];
// set the image chosen for other classes to set uiimages with
NSData *imageToStore = UIImageJPEGRepresentation(outputImage, 100);
[defaults removeObjectForKey:#"imageToUse"];
[defaults setObject:imageToStore forKey:#"imageToUse"];
}