How to add multiple filters to UIImage GPUImage?

Question

I noticed a lot of people asking questions about linking filters with GPUImage. I can't quite figure out how to do it succinctly. Finally got it working tonight. Just wanted to share my code so people can link to the solution.

Answer 1

UIImage *faceImage = [UIImage imageNamed:@"469453586_640.jpg"];
UIImageView *face = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, faceImage.size.width/2.0, faceImage.size.height/2.0)];
[face setImage:faceImage];
[self.view addSubview:face];

GPUImagePicture *stillImageSource = [[GPUImagePicture alloc] initWithImage:faceImage];

GPUImageBrightnessFilter *brightnessFilter = [[GPUImageBrightnessFilter alloc] init];
[brightnessFilter setBrightness:.15];
GPUImageGrayscaleFilter *grayscaleFilter = [[GPUImageGrayscaleFilter alloc] init];

GPUImagePosterizeFilter *posterizeFilter = [[GPUImagePosterizeFilter alloc] init];
[posterizeFilter setColorLevels:1];


[stillImageSource addTarget:brightnessFilter];
[brightnessFilter addTarget:grayscaleFilter];
[grayscaleFilter addTarget:posterizeFilter];

// these need to be changed if you change the order of your filters
//    [brightnessFilter useNextFrameForImageCapture];
//    [grayscaleFilter useNextFrameForImageCapture];
[posterizeFilter useNextFrameForImageCapture];

[stillImageSource processImage];

[face setImage: [posterizeFilter imageFromCurrentFramebuffer]];