ios – CIFilter coloration dice information loading

I’ve round 50 3D LUTs (saved as png photos, every being 900KB in dimension) and use CIColorCube filter to generate a filtered picture. I take advantage of UICollectionView to show filtered thumbnails (100×100) for every LUT (like in Images app). The issue is UICollectionView scrolling turns into extraordinarily sluggish(no the place near smoothness of Images app) once I generate filtered photos as person scrolls. I considered pre producing filtered photos however the issue is it takes round 150 milliseconds to generate cubeData from LUT png, so for 50 thumbnails it takes round 7-8 seconds to arrange filtered thumbnails which is lengthy. And that is precisely the offender for scrolling efficiency as effectively. I’m questioning what I can do to make it clean like in Images app or different picture modifying apps. Right here is my code to generate dice information from LUT png. I consider there’s extra of a CoreImage/Metallic trick to repair the problem than UIKit/DispatchQueue/NSOperation based mostly fixes.

      public static func colorCubeDataFromLUTPNGImage(_ picture : UIImage, lutSize:Int) -> Information? {

        let dimension = lutSize

        let lutImage = picture.cgImage!
        let lutWidth    = lutImage.width
        let lutHeight   = lutImage.top
        let rowCount    = lutHeight / dimension
        let columnCount = lutWidth / dimension

        if ((lutWidth % dimension != 0) || (lutHeight % dimension != 0) || (rowCount * columnCount != dimension)) {
            NSLog("Invalid colorLUT")
            return nil
        }

        let bitmap  = getBytesFromImage(picture: picture)!
        let floatSize = MemoryLayout<Float>.dimension

        let cubeData = UnsafeMutablePointer<Float>.allocate(capability: dimension * dimension * dimension * 4 * floatSize)
        var z = 0
        var bitmapOffset = 0

        for _ in 0 ..< rowCount {
            for y in 0 ..< dimension {
                let tmp = z
                for _ in 0 ..< columnCount {
                    for x in 0 ..< dimension {

                        let alpha   = Float(bitmap[bitmapOffset]) / 255.0
                        let purple     = Float(bitmap[bitmapOffset+1]) / 255.0
                        let inexperienced   = Float(bitmap[bitmapOffset+2]) / 255.0
                        let blue    = Float(bitmap[bitmapOffset+3]) / 255.0

                        let dataOffset = (z * dimension * dimension + y * dimension + x) * 4

                        cubeData[dataOffset + 3] = alpha
                        cubeData[dataOffset + 2] = purple
                        cubeData[dataOffset + 1] = inexperienced
                        cubeData[dataOffset + 0] = blue
                        bitmapOffset += 4
                    }
                    z += 1
                }
                z = tmp
            }
            z += columnCount
        }

    let colorCubeData = Information(bytesNoCopy: cubeData, rely: dimension * dimension * dimension * 4 * floatSize, deallocator: Information.Deallocator.free)
    
    return colorCubeData
}


fileprivate static func getBytesFromImage(picture:UIImage?) -> [UInt8]?
{
    var pixelValues: [UInt8]?
    if let imageRef = picture?.cgImage  CGBitmapInfo.byteOrder32Little.rawValue
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        var intensities = [UInt8](repeating: 0, rely: totalBytes)

        let contextRef = CGContext(information: &intensities, width: width, top: top, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, house: colorSpace, bitmapInfo: bitmapInfo)
        contextRef?.draw(imageRef, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(width), top: CGFloat(top)))

        pixelValues = intensities
    
    return pixelValues!
}

And right here is my code for UICollectionViewCell setup:

   func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let lutPath = self.lutPaths[indexPath.item]
    
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "FilterCell", for: indexPath) as! FilterCell
    
    if let lutImage = UIImage(contentsOfFile: lutPath) {
        let renderer = CIFilter(identify: "CIColorCube")!
        let lutData = ColorCubeHelper.colorCubeDataFromLUTPNGImage(lutImage, lutSize: 64)
       
        renderer.setValue(lutData!, forKey: "inputCubeData")
        renderer.setValue(64, forKey: "inputCubeDimension")
        renderer.setValue(inputCIImage, forKey: kCIInputImageKey)
        let outputImage = renderer.outputImage!
        
        let cgImage = self.ciContext.createCGImage(outputImage, from: outputImage.extent)!
        cell.configure(picture: UIImage(cgImage: cgImage))
        
    } else {
        NSLog("LUT not discovered at (indexPath.merchandise)")
    }
    
    return cell
}