MetalPetalSwiftUI.swift

//  Created by Jeri Purnama on 24/02/23.
/* 
  Use this Pod to Filter Image 
  https://cocoapods.org/pods/MetalPetal
*/

import SwiftUI
import MetalPetal

struct ContentViewOne: View {
    
    @State var inputImage = UIImage(named: "subWall1")!
    
    var body: some View {
        VStack {
            Image(uiImage: inputImage)
                .resizable()
                .aspectRatio(contentMode: .fit)
                .frame(width: 300, height: 300)
            
            Button("Apply Filter") {
                inputImage = applyFilter(inputImage)
            }
        }
    }
    
    func applyFilter(_ image: UIImage) -> UIImage {
        let context = try! MTIContext(device: MTLCreateSystemDefaultDevice()!)
        
        // Load the input image into a MetalPetal image object
        let input = MTIImage(__cgImage: image.cgImage!, options: [.SRGB: false], isOpaque: true)
        
        // Create a MetalPetal filter
        let filter = MTICLAHEFilter() // name filter
        filter.inputImage = input
        
        // Apply the filter
        let output = filter.outputImage!
        
        // Render the output image to a CGImage
        let cgImage = try! context.makeCGImage(from: output)
        
        // Convert the CGImage to a UIImage
        let outputImage = UIImage(cgImage: cgImage)
        
        return outputImage
    }
}


struct ContentViewTwo: View {
    
    @State var inputImage = UIImage(named: "subWall1")!
    @State var currentFilter: MTIUnaryFilter = MTIColorInvertFilter()
    @State var filterStrength: Double = 1.0
    
    var body: some View {
        VStack {
            Image(uiImage: inputImage)
                .resizable()
                .aspectRatio(contentMode: .fit)
                .frame(width: 300, height: 300)
            
            Slider(value: $filterStrength, in: 0.0...1.0, step: 0.01, onEditingChanged: { _ in
                applyFilter()
            })
            
            HStack {
                Button("Invert") {
                    currentFilter = MTIColorInvertFilter()
                    applyFilter()
                }
                Button("Grayscale") {
                    currentFilter = MTIDotScreenFilter()
                    applyFilter()
                }
                Button("Sepia") {
                    currentFilter = MTICLAHEFilter()
                    applyFilter()
                }
            }
        }
    }
    
    func applyFilter() {
        let context = try! MTIContext(device: MTLCreateSystemDefaultDevice()!)
        
        // Load the input image into a MetalPetal image object
        let input = MTIImage(__cgImage: inputImage.cgImage!, options: [.SRGB: false], isOpaque: true)
        
        // Create a MetalPetal filter
        let filter = currentFilter
        filter.inputImage = input
//        filter.inputIntensity = filterStrength
        
        // Apply the filter
        let output = filter.outputImage!
        
        // Render the output image to a CGImage
        let cgImage = try! context.makeCGImage(from: output)
        
        // Convert the CGImage to a UIImage
        let outputImage = UIImage(cgImage: cgImage)
        
        inputImage = outputImage
    }
}


struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentViewTwo()
    }
}