Create new project in XCode that will use single view application template.

Define project name and we are ready to start working on it.

The image we will use to test the effects is 640*640 pixels, so we'll add it to project by right clicking Supporting Files Folder and picking option Add Files.

Add six UIButtons and one UIImageView to your main xib. Five of those buttons will be used to apply filters and one will be used to see original image.

Set imageviews image to image you added to the project so it display as application runs.

In Project navigator select your project and under Build Phases click + at end of Link Binary With Libraries to add additional frameworks. Framework we are adding is named CoreImage.framework.

In header file (.h) of you view controller add IBOutlet for UIImageView and add six IBAction methods.

@property (nonatomic, retain) IBOutlet UIImageView *theImageView;

- (IBAction)originalImage:(id)sender;
- (IBAction)filterOne:(id)sender;
- (IBAction)filterTwo:(id)sender;
- (IBAction)filterThree:(id)sender;
- (IBAction)filterFour:(id)sender;
- (IBAction)filterFive:(id)sender;

In main file (.m) synthesize defined image view.

@synthesize theImageView;

First IBAction named originalImage will display original image in image view. In case your image is named different change "photo-core-image.jpg" to correct name.

- (IBAction)originalImage:(id)sender
{
    theImageView.image = [UIImage imageNamed:@"photo-core-image.jpg"];
}

CIColorControls is first filter we'll define.

CIColorControls Adjusts saturation, brightness, and contrast values.

We have to define CIImage that will initialize with value of our original image. After that we define CIFilter with name brightnesContrastFilter and we set default values to it.

Each filter have several keys, for key inputImage we set value of CIImage, for key inputBrightness we set NSNumber 0.5 and for key inputContrast we set NSNumber 2.0.

We have to create another CIImage that will hold value for output image and we show this image in our image view.

- (IBAction)filterOne:(id)sender
{
    CIImage *inputImage = [[CIImage alloc] initWithImage:
                              [UIImage imageNamed:@"photo-core-image.jpg"]];

    CIFilter *brightnesContrastFilter = [CIFilter filterWithName:@"CIColorControls"];
    [brightnesContrastFilter setDefaults];
    [brightnesContrastFilter setValue: inputImage forKey: @"inputImage"];
    [brightnesContrastFilter setValue: [NSNumber numberWithFloat:0.5f]
                                          forKey:@"inputBrightness"];
    [brightnesContrastFilter setValue: [NSNumber numberWithFloat:2.0f] 
                                          forKey:@"inputContrast"];

    CIImage *outputImage = [brightnesContrastFilter valueForKey: @"outputImage"];

    CIContext *context = [CIContext contextWithOptions:nil];

    theImageView.image = [UIImage imageWithCGImage:[context 
                                         createCGImage:outputImage 
                                         fromRect:outputImage.extent]];

    [inputImage release];
}

Result of CIColorControls filter looks like this:

CIHueAdjust Changes the overall hue, or tint, of the source pixels.

CIHueAdjust filter beside key inputImage have inputAngle since Hue is defined as color wheel. With same logic for previous filter we create this one and we set value for inputAngle to 3.0.

- (IBAction)filterTwo:(id)sender
{
    CIImage *inputImage = [[CIImage alloc] initWithImage:
                              [UIImage imageNamed:@"photo-core-image.jpg"]];

    CIFilter *hueFilter = [CIFilter filterWithName:@"CIHueAdjust"];
    [hueFilter setDefaults];
    [hueFilter setValue: inputImage forKey: @"inputImage"];
    [hueFilter setValue: [NSNumber numberWithFloat: 3.0f] forKey: @"inputAngle"];

    CIImage *outputImage = [hueFilter valueForKey: @"outputImage"];

    CIContext *context = [CIContext contextWithOptions:nil];

    theImageView.image = [UIImage imageWithCGImage:[context 
                                         createCGImage:outputImage 
                                         fromRect:outputImage.extent]];

    [inputImage release];
}

Result of CIHueAdjust filter looks like this:

CIColorInvert inverts the colors in an image.

We dont define any other key here except input image key.

- (IBAction)filterThree:(id)sender
{
    CIImage *inputImage = [[CIImage alloc] initWithImage:
                              [UIImage imageNamed:@"photo-core-image.jpg"]];

    CIFilter *invertFilter = [CIFilter filterWithName:@"CIColorInvert"];
    [invertFilter setDefaults];
    [invertFilter setValue: inputImage forKey: @"inputImage"];

    CIImage *outputImage = [invertFilter valueForKey: @"outputImage"];

    CIContext *context = [CIContext contextWithOptions:nil];

    theImageView.image = [UIImage imageWithCGImage:[context 
                                         createCGImage:outputImage 
                                         fromRect:outputImage.extent]];

    [inputImage release];
}

Result of CIColorInvert filter looks like this:

CIExposureAdjust adjusts the exposure setting for an image similar to the way you control exposure for a camera when you change the F-stop. Key we define here is named inputEV.

- (IBAction)filterFour:(id)sender
{
    CIImage *inputImage = [[CIImage alloc] initWithImage:
                              [UIImage imageNamed:@"photo-core-image.jpg"]];

    CIFilter *exposureAdjustFilter = [CIFilter filterWithName:@"CIExposureAdjust"];
    [exposureAdjustFilter setDefaults];
    [exposureAdjustFilter setValue: inputImage forKey: @"inputImage"];
    [exposureAdjustFilter setValue:[NSNumber numberWithFloat: 2.0f]
                              forKey:@"inputEV"];    
    CIImage *outputImage = [exposureAdjustFilter valueForKey: @"outputImage"];

    CIContext *context = [CIContext contextWithOptions:nil];

    theImageView.image = [UIImage imageWithCGImage:[context 
                                         createCGImage:outputImage 
                                         fromRect:outputImage.extent]];

    [inputImage release];
}

Result of CIExposureAdjust filter looks like this:

CIHighlightShadowAdjust adjust the tonal mapping of an image while preserving spatial detail. For this filter we set values for keys inputHighlightAmount and inputShadowAmount.

- (IBAction)filterFive:(id)sender
{
    CIImage *inputImage = [[CIImage alloc] initWithImage:
                              [UIImage imageNamed:@"photo-core-image.jpg"]];

    CIFilter *highlightShadowAdjustFilter = [CIFilter
                 filterWithName:@"CIHighlightShadowAdjust"];
    [highlightShadowAdjustFilter setDefaults];
    [highlightShadowAdjustFilter setValue: inputImage forKey: @"inputImage"];
    [highlightShadowAdjustFilter setValue:[NSNumber numberWithFloat: 1.0f]
                 forKey:@"inputHighlightAmount"];    
    [highlightShadowAdjustFilter setValue:[NSNumber numberWithFloat: 0.5f] 
                 forKey:@"inputShadowAmount"];    
    CIImage *outputImage = [highlightShadowAdjustFilter
                 valueForKey: @"outputImage"];

    CIContext *context = [CIContext contextWithOptions:nil];

    theImageView.image = [UIImage imageWithCGImage:[context 
                                         createCGImage:outputImage 
                                         fromRect:outputImage.extent]];

    [inputImage release];
}

Result of CIHighlightShadowAdjust filter looks like this:

We created an improved project of what we covered above adding a cool UI and features like:

• Load image from gallery
• shot a new image
• apply filter
• save image to gallery
• share info on social networks

Click Here to Download the Project.