How to use ChromaKey and Sepia filter with GPUImage at the same time?

Question

I'm using for the first time the GPUImage framework of Brad Larson.

I don't know if it's possible, but I would like to use the GPUImageChromaKeyFilter and GPUImageSepiaFilter. I can use them separately, but at the same time, it doesn't work. The sepia tone works, but the chromaKey seems doesn't work.

EDIT 2: WORKING Here is my code:

- (void)setupCameraAndFilters:(AVCaptureDevicePosition)cameraPostion {

    videoCamera = [[GPUImageVideoCamera alloc] initWithSessionPreset:AVCaptureSessionPreset640x480 cameraPosition:cameraPostion];
    videoCamera.outputImageOrientation = UIInterfaceOrientationLandscapeRight;

    // ChromaKey
    chromaKeyFilter = [[GPUImageChromaKeyBlendFilter alloc] init];
    [(GPUImageChromaKeyBlendFilter *)chromaKeyFilter setColorToReplaceRed:0.0 green:1.0 blue:0.0];

    [videoCamera addTarget:chromaKeyFilter];

    // Input image (replace the green background)
    UIImage *inputImage;
    inputImage = [UIImage imageNamed:@"chromaBackground.jpg"];
    sourcePicture = [[GPUImagePicture alloc] initWithImage:inputImage smoothlyScaleOutput:YES];
    [sourcePicture processImage];
    [sourcePicture addTarget:chromaKeyFilter];

    // Sepia filter
    sepiaFilter = [[GPUImageSepiaFilter alloc] init];
    [chromaKeyFilter addTarget:sepiaFilter];

    [sepiaFilter addTarget:self.filteredVideoView];

    [videoCamera startCameraCapture];
}

Answer 1

Your problem is that the above code doesn't really make sense. In the first example, you have your still image going into the single-input GPUImageChromaKeyFilter, then you try to target both that source image and your video feed to the single-input GPUImageSepiaFilter. One of those two inputs will be overridden by the other.

GPUImageFilterGroups are merely convenience classes for grouping sequences of filters together an an easy-to-reuse package, and won't solve anything here.

If you're trying to blend video with a chroma-keyed image, you need to use a GPUImageChromaKeyBlendFilter, which takes two inputs and blends them together based on the keying. You can then send that single output image to the sepia tone filter, or however you want to sequence that.