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iosswiftgpuimage

Chaining filters with GPUImage in swift

(First post to Stack Overflow - So, Hi 'waves nervously')

I'm using the GPUImage library with some success - and have managed to get a simple filter working on a static image using swift.

However I'm having problems trying to chain multiple filters together. The included examples in the library don't seem to cover this. There are plenty of objective C examples but not swift.

Can anyone please give an example of how to apply:

2 blend filters plus a brightness, contrast and saturation filter to a single static image?

I think this is sufficiently complex to cover most uses of the library in Swift. Thanks.

Solution

  • Allocating and chaining filters in Swift is the same as it is in Objective-C, it's just syntactic conversion. For example, the following is how you'd chain two still image inputs to a blend filter in Objective-C, then have the result of that blend be directed to a contrast filter, with a capture of your final image:

    GPUImageOverlayBlendFilter *blendFilter = [[GPUImageOverlayBlendFilter alloc] init];
[stillImageSource1 addTarget:blendFilter];
[stillImageSource2 addTarget:blendFilter];

GPUImageContrastFilter *contrastFilter = [[GPUImageContrastFilter alloc] init];
[blendFilter addTarget:contrastFilter];

[contrastFilter useNextFrameForImageCapture];
[stillImageSource1 processImage];
[stillImageSource2 processImage];

UIImage *currentFilteredImage = [contrastFilter imageFromCurrentFramebuffer];

    This is the equivalent in Swift:

    let blendFilter = GPUImageOverlayBlendFilter()
stillImageSource1.addTarget(blendFilter)
stillImageSource2.addTarget(blendFilter)

let contrastFilter = GPUImageContrastFilter()
blendFilter.addTarget(contrastFilter)

contrastFilter.useNextFrameForImageCapture()
stillImageSource1.processImage()
stillImageSource2.processImage()

let currentFilteredImage = contrastFilter.imageFromCurrentFramebuffer()

    As you can see, it's all syntax, nothing different in how you actually call things. You can use the Objective-C example code as a basis for what you want to do, and just rewrite that in your Swift equivalents. The Swift examples that I ship with the framework are either really simple (the tiny application that uses a single filter on live video) or fairly complex (my test case application that executes every filter and operation in the framework).