快速链接具有GPUImage的滤镜

Question

(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.

Answer 1

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).

Answer 2

When you use the FilterOperations.swift class from the demo, then you could initialize filters like this:

// Quick reference to the used filter configurations
var filterExposure = filterOperations.firstMatch {item in return item.listName == "Exposure"}!
var filterHighlightShadow = filterOperations.firstMatch {item in return item.listName == "Highlights and shadows"}!
var filterSaturation = filterOperations.firstMatch {item in return item.listName == "Saturation"}!
var filterContrast  = filterOperations.firstMatch {item in return item.listName == "Contrast"}!
var filterAdaptiveThreshold  = filterOperations.firstMatch {item in return item.listName == "Adaptive threshold"}!

And then setup these filters like this:

    (self.filterExposure.filter as GPUImageExposureFilter).exposure = 0.8 // -10 - 10
    (self.filterHighlightShadow.filter as GPUImageHighlightShadowFilter).highlights = 1.0 // 0 - 1
    (self.filterSaturation.filter as GPUImageSaturationFilter).saturation = 0.0 // 0 - 2
    (self.filterContrast.filter as GPUImageContrastFilter).contrast = 2.0  // 0 - 4
    (self.filterAdaptiveThreshold.filter as GPUImageAdaptiveThresholdFilter).blurRadiusInPixels = 8.0

And then you could chain the filters like this:

    videoCamera.addTarget((self.filterExposure.filter as GPUImageInput))
    self.filterExposure.filter.addTarget((self.filterHighlightShadow.filter as GPUImageInput))
    self.filterHighlightShadow.filter.addTarget((self.filterSaturation.filter as GPUImageInput))
    self.filterSaturation.filter.addTarget((self.filterContrast.filter as GPUImageInput))
    self.filterContrast.filter.addTarget((self.filterAdaptiveThreshold.filter as GPUImageInput))
    self.filterAdaptiveThreshold.filter.addTarget(self.filterView)