Search code examples
iosfilteringgpuimage

GPUImage GPUImageChromaKeyBlendFilter With Still Image

I would like to create a GPUImageView to display a filter in real time (as opposed to keep reading imageFromCurrentlyProcessedOutput)

Is it possible to use GPUImage's GPUImageChromaKeyBlendFilter with a still source image automatically updating a GPUImageView?

Here is my code reading this into a UIImage;

    UIImage *inputImage = [UIImage imageNamed:@"1.JPG"];
    UIImage *backgroundImage = [UIImage imageNamed:@"2.JPG"];

    GPUImagePicture *stillImageSource = [[GPUImagePicture alloc] initWithImage:inputImage];
    GPUImageChromaKeyBlendFilter *stillImageFilter = [[GPUImageChromaKeyBlendFilter alloc] init];
    [stillImageFilter setThresholdSensitivity:0.5];
    [stillImageFilter setColorToReplaceRed:0.0 green:1.0 blue:0.0];


    [stillImageSource addTarget:stillImageFilter];
    [stillImageSource processImage];


    UIImage *currentFilteredVideoFrame = [stillImageFilter imageByFilteringImage: backgroundImage ];

Everything I have tried so far requires you to add the 'backgroundImage' as a target to the filter (as you would if you were using the StillCamera). If you add the backgroundImage as a target, GPUImage just uses this new images as it's base image.

Can anyone help?

Thanks,

Solution

  • Don't use -imageByFilteringImage: with a two-input filter, like blends. It's a convenience method to quickly set up a small filter chain based on a UIImage and grab a UIImage out. You're not going to want it for something targeting a GPUImageView, anyway.

    For the chroma key blend, you'll need to target your input image (the one with the color to be replaced) and background image to the blend, in that order using -addTarget, with GPUImagePicture instances for both. You then target your blend to the GPUImageView.

    One note, you'll need to maintain strong references to your GPUImagePictures past the setup method, if you want to keep updating the filter after this point, so you may need to make them instance variables on your controller class.

    Once you've set things up in this way, the result will go to your GPUImageView. Every time you call -processImage on one of the two images, the display in your GPUImageView will be updated. Therefore, you can call that after every change in filter settings, like if you had a slider to update filter values, and the image will be updated in realtime.