GPUImage Filter chaining in Swift. Uses LinkedList from Wayne Bishop's SwiftStructures

FilterBuilder.swift

struct FilterBuilder {
    let list = LinkedList<GPUImageFilter>()
    mutating func build(filters: GPUImageFilter...) -> GPUImageFilterGroup {
        let group = GPUImageFilterGroup()
        for filter in filters { list.addLink(filter) }
        
        var i = 0
        while (list.linkAtIndex(i).next != nil ){
            let curr = list.linkAtIndex(i)
            group.addFilter(curr.key)
            curr.key.addTarget(curr.next?.key)
            i++
        }
        group.initialFilters = [filters.first as! AnyObject]
        group.terminalFilter = filters.last
        return group
    }
    
    // For chaining still image filters, in a clean reusable way.
    func filterImage(image: UIImage, filters:GPUImageFilter...) -> UIImage {
        var result : UIImage = image
        var picture : GPUImagePicture
        
        for filter in filters {
            picture = GPUImagePicture(image: result)
            picture.addTarget(filter)
            filter.forceProcessingAtSize(image.size)
            filter.useNextFrameForImageCapture()
            picture.processImage()
            result = filter.imageFromCurrentFramebuffer()
        }
        return result
    }
}