I would like to use a lookup table png (example) as color cube data for the CIColorCube filter in Swift. All I tried (and found) so far are examples with a computed color cube as in this example.
How can I read a png as lookup data?
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问题:
回答1:
I now used this and this project to adapt their Objective-C implementation for Swift:
func colorCubeFilterFromLUT(imageName : NSString) -> CIFilter? { let kDimension : UInt = 64 let lutImage = UIImage(named: imageName)!.CGImage let lutWidth = CGImageGetWidth(lutImage!) let lutHeight = CGImageGetHeight(lutImage!) let rowCount = lutHeight / kDimension let columnCount = lutWidth / kDimension if ((lutWidth % kDimension != 0) || (lutHeight % kDimension != 0) || (rowCount * columnCount != kDimension)) { NSLog("Invalid colorLUT %@", imageName); return nil } let bitmap = self.createRGBABitmapFromImage(lutImage) let size = Int(kDimension) * Int(kDimension) * Int(kDimension) * sizeof(Float) * 4 let data = UnsafeMutablePointer<Float>(malloc(UInt(size))) var bitmapOffset : Int = 0 var z : UInt = 0 for (var row: UInt = 0; row < rowCount; row++) { for (var y: UInt = 0; y < kDimension; y++) { var tmp = z for (var col: UInt = 0; col < columnCount; col++) { for (var x: UInt = 0; x < kDimension; x++) { let alpha = Float(bitmap[Int(bitmapOffset)]) / 255.0 let red = Float(bitmap[Int(bitmapOffset+1)]) / 255.0 let green = Float(bitmap[Int(bitmapOffset+2)]) / 255.0 let blue = Float(bitmap[Int(bitmapOffset+3)]) / 255.0 var dataOffset = Int(z * kDimension * kDimension + y * kDimension + x) * 4 data[dataOffset] = red data[dataOffset + 1] = green data[dataOffset + 2] = blue data[dataOffset + 3] = alpha bitmapOffset += 4 } z++ } z = tmp } z += columnCount } let colorCubeData = NSData(bytesNoCopy: data, length: size, freeWhenDone: true) // create CIColorCube Filter var filter = CIFilter(name: "CIColorCube") filter.setValue(colorCubeData, forKey: "inputCubeData") filter.setValue(kDimension, forKey: "inputCubeDimension") return filter } func createRGBABitmapFromImage(inImage: CGImage) -> UnsafeMutablePointer<Float> { //Get image width, height let pixelsWide = CGImageGetWidth(inImage) let pixelsHigh = CGImageGetHeight(inImage) // Declare the number of bytes per row. Each pixel in the bitmap in this // example is represented by 4 bytes; 8 bits each of red, green, blue, and // alpha. let bitmapBytesPerRow = Int(pixelsWide) * 4 let bitmapByteCount = bitmapBytesPerRow * Int(pixelsHigh) // Use the generic RGB color space. let colorSpace = CGColorSpaceCreateDeviceRGB() // Allocate memory for image data. This is the destination in memory // where any drawing to the bitmap context will be rendered. let bitmapData = malloc(CUnsignedLong(bitmapByteCount)) // bitmap let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue) // Create the bitmap context. We want pre-multiplied RGBA, 8-bits // per component. Regardless of what the source image format is // (CMYK, Grayscale, and so on) it will be converted over to the format // specified here by CGBitmapContextCreate. let context = CGBitmapContextCreate(bitmapData, pixelsWide, pixelsHigh, 8, UInt(bitmapBytesPerRow), colorSpace, bitmapInfo) let rect = CGRect(x:0, y:0, width:Int(pixelsWide), height:Int(pixelsHigh)) // Draw the image to the bitmap context. Once we draw, the memory // allocated for the context for rendering will then contain the // raw image data in the specified color space. CGContextDrawImage(context, rect, inImage) // Now we can get a pointer to the image data associated with the bitmap // context. // var data = CGBitmapContextGetData(context) // var dataType = UnsafeMutablePointer<Float>(data) // return dataType var convertedBitmap = malloc(UInt(bitmapByteCount * sizeof(Float))) vDSP_vfltu8(UnsafePointer<UInt8>(bitmapData), 1, UnsafeMutablePointer<Float>(convertedBitmap), 1, vDSP_Length(bitmapByteCount)) free(bitmapData) return UnsafeMutablePointer<Float>(convertedBitmap) } Also see this answer.
回答2:
While it's not the exact same type of LUT image you have linked, CocoaLUT, my 1D and 3D LUT framework for Cocoa, can read and write 3 different types of LUT images.
When I first started making CocoaLUT and wrote the Image-Based LUT readers/writers, I didn't know how to do low level bitmap image work in Cocoa. I just used NSBitmapImageRep, which means you're out of luck if you need to do this in iOS until I decide to go back and revamp it to work with Core Graphics knowing what I know now.
In the case that you are writing this for a Mac app, you should just be able to do (in Swift):
let imageLUT = LUT3D(fromURL:NSURL.fileURLWithPath("/path/to/image.tiff"), error: nil) let cubeFilter = imageLUT.coreImageFilterWithCurrentColorSpace() If you need to first generate a blank or "identity" LUT Image to perform grading on, you should do (in Swift):
let identity33 = LUT3D(identityOfSize: 33, inputLowerBound: 0, inputUpperBound: 1); let success = identity33.writeToURL(NSURL.fileURLWithPath("/path/to/output.tiff"), atomically: true, formatterID: "unwrappedCube", options: nil, conformLUT: true) Please note that you need to do this with TIFF files throughout! Again, generalizing the code for Core Graphics will fix all this, if I finally get around to it.
回答3:
Thought I would update this for Swift 3.0 also this works for JPG's and PNG's 3D Color LUTs
fileprivate func colorCubeFilterFromLUT(imageName : String) -> CIFilter? { let size = 64 let lutImage = UIImage(named: imageName)!.cgImage let lutWidth = lutImage!.width let lutHeight = lutImage!.height let rowCount = lutHeight / size let columnCount = lutWidth / size if ((lutWidth % size != 0) || (lutHeight % size != 0) || (rowCount * columnCount != size)) { NSLog("Invalid colorLUT %@", imageName); return nil } let bitmap = getBytesFromImage(image: UIImage(named: imageName))! let floatSize = MemoryLayout<Float>.size let cubeData = UnsafeMutablePointer<Float>.allocate(capacity: size * size * size * 4 * floatSize) var z = 0 var bitmapOffset = 0 for _ in 0 ..< rowCount { for y in 0 ..< size { let tmp = z for _ in 0 ..< columnCount { for x in 0 ..< size { let alpha = Float(bitmap[bitmapOffset]) / 255.0 let red = Float(bitmap[bitmapOffset+1]) / 255.0 let green = Float(bitmap[bitmapOffset+2]) / 255.0 let blue = Float(bitmap[bitmapOffset+3]) / 255.0 let dataOffset = (z * size * size + y * size + x) * 4 cubeData[dataOffset + 3] = alpha cubeData[dataOffset + 2] = red cubeData[dataOffset + 1] = green cubeData[dataOffset + 0] = blue bitmapOffset += 4 } z += 1 } z = tmp } z += columnCount } let colorCubeData = NSData(bytesNoCopy: cubeData, length: size * size * size * 4 * floatSize, freeWhenDone: true) // create CIColorCube Filter let filter = CIFilter(name: "CIColorCube") filter?.setValue(colorCubeData, forKey: "inputCubeData") filter?.setValue(size, forKey: "inputCubeDimension") return filter } fileprivate func getBytesFromImage(image:UIImage?) -> [UInt8]? { var pixelValues: [UInt8]? if let imageRef = image?.cgImage { let width = Int(imageRef.width) let height = Int(imageRef.height) let bitsPerComponent = 8 let bytesPerRow = width * 4 let totalBytes = height * bytesPerRow let bitmapInfo = CGImageAlphaInfo.premultipliedLast.rawValue | CGBitmapInfo.byteOrder32Little.rawValue let colorSpace = CGColorSpaceCreateDeviceRGB() var intensities = [UInt8](repeating: 0, count: totalBytes) let contextRef = CGContext(data: &intensities, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo) contextRef?.draw(imageRef, in: CGRect(x: 0.0, y: 0.0, width: CGFloat(width), height: CGFloat(height))) pixelValues = intensities } return pixelValues! }