Xamarin.iOS recipe using CIImage Filters to apply an Old Film effect

View the Project on GitHub dannycabrera/iOS.OldFilmFilter


Xamarin.iOS recipe using Core Image Filters to apply an Old Film effect

This is my sample recipe for the Xamarin Recipe Cook-Off. This sample will show how to take an image with your device and apply an old film effect. To handle the picture taking code I used the Xamarin.Mobile component.


iOS.OldFilmFilter Screenshot

How to apply Old Film Effect

The process involves applying a Sepia Tone filter, generating random white-specks (colored noise) and blending them together.

  1. Apply the Sepia Tone filter to the image:

    var sep = new CISepiaTone() 
    Image = ciimage,
    Intensity = 1F
  2. Create random white-specks. This process involves generating colored noise by calling RandomGenerator() and then processing the noise so that we only get white specks calling ColorMatrix().

    public CIImage ColorMatrix()
    var rVector = new CIVector (0F, 0.1F, 0F, 0F); 
    var gVector = new CIVector (0F, 0.1F, 0F, 0F);  
    var bVector = new CIVector (0F, 0.1F, 0F, 0F); 
    var biasVector = new CIVector (0F, 0F, 0F, 0F); 
    var colorMatrix = new CIColorMatrix ()
        Image = RandomGenerator(),
        RVector = rVector,
        GVector = gVector,
        BVector = bVector,
        BiasVector = biasVector
    return colorMatrix.OutputImage;
    public CIImage RandomGenerator()
    var random = new CIRandomGenerator ();
    return Crop (random);
  3. Once we have the Sepia Tone and the white-specks images, we blend them using CISourceOverCompositing().

    var comp = new CISourceOverCompositing () {
    Image = ColorMatrix(),
    BackgroundImage = sep.OutputImage
  4. The final step is to render the filters into an image and display a preview on the image view.

    var output = comp.OutputImage;
    var context = CIContext.FromOptions(null);
    img.Dispose (); // clear image
    img = UIImage.FromImage (context.CreateCGImage (output, output.Extent));
    imageView.Image = img;