Colour correction of Photoshop LUT filter using CIFilter - ios

Question

Using photoshop to create LUT filter and use iOS CIFilter to read the LUT image, filter image created by iOS is not corresponding to the filer image created by photoshop.
How can I trace the issue?
This is the original image
This is the image with filter I created from photoshop
This is the image with filter I created from iPhone
This is the LUT image I am using

Answer 1

please Try This its work for me
public class LUTsHelper {
public static func applyLUTsFilter(lutImage: String, dimension: Int, colorSpace: CGColorSpace) -> CIFilter? {
guard let image = UIImage(named: lutImage) else {
return nil
}
guard let cgImage = image.cgImage else {
return nil
}
guard let bitmap = createBitmap(image: cgImage, colorSpace: colorSpace) else {
return nil
}
let width = cgImage.width
let height = cgImage.height
let rowNum = width / dimension
let columnNum = height / dimension
let dataSize = dimension * dimension * dimension * MemoryLayout<Float>.size * 4
var array = Array<Float>(repeating: 0, count: dataSize)
var bitmapOffest: Int = 0
var z: Int = 0
for _ in stride(from: 0, to: rowNum, by: 1) {
for y in stride(from: 0, to: dimension, by: 1) {
let tmp = z
for _ in stride(from: 0, to: columnNum, by: 1) {
for x in stride(from: 0, to: dimension, by: 1) {
let dataOffset = (z * dimension * dimension + y * dimension + x) * 4
let position = bitmap
.advanced(by: bitmapOffest)
array[dataOffset + 0] = Float(position
.advanced(by: 0)
.pointee) / 255
array[dataOffset + 1] = Float(position
.advanced(by: 1)
.pointee) / 255
array[dataOffset + 2] = Float(position
.advanced(by: 2)
.pointee) / 255
array[dataOffset + 3] = Float(position
.advanced(by: 3)
.pointee) / 255
bitmapOffest += 4
}
z += 1
}
z = tmp
}
z += columnNum
}
free(bitmap)
let data = Data.init(bytes: array, count: dataSize)
guard
let cubeFilter = CIFilter(name: "CIColorCubeWithColorSpace")
else {
return nil
}
cubeFilter.setValue(dimension, forKey: "inputCubeDimension")
cubeFilter.setValue(data, forKey: "inputCubeData")
cubeFilter.setValue(colorSpace, forKey: "inputColorSpace")
return cubeFilter
}
private static func createBitmap(image: CGImage, colorSpace: CGColorSpace) -> UnsafeMutablePointer<UInt8>? {
let width = image.width
let height = image.height
let bitsPerComponent = 8
let bytesPerRow = width * 4
let bitmapSize = bytesPerRow * height
guard let data = malloc(bitmapSize) else {
return nil
}
guard let context = CGContext(
data: data,
width: width,
height: height,
bitsPerComponent: bitsPerComponent,
bytesPerRow: bytesPerRow,
space: colorSpace,
bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue,
releaseCallback: nil,
releaseInfo: nil) else {
return nil
}
context.draw(image, in: CGRect(x: 0, y: 0, width: width, height: height))
return data.bindMemory(to: UInt8.self, capacity: bitmapSize)
}}
now us this class
let colorSpace: CGColorSpace = CGColorSpace.init(name: CGColorSpace.sRGB) ?? CGColorSpaceCreateDeviceRGB()
let lutFilter = LUTsHelper.applyLUTsFilter(lutImage: "demo.png", dimension: 64, colorSpace: colorSpace)
lutFilter?.setValue(outputImage, forKey: "inputImage")
let lutOutputImage = lutFilter?.outputImage
if let output = lutOutputImage {
outputImage = output
}