Swift Image Processing

Question

I'm new to Swift and I'm trying to create a class/struct Filter that takes filter formula and intensity in constructor. This class has a method to apply the given formula with given intensity on an image in its parameter and then return the modified image.

We have a class called RGBAImage.swift which has methods to convert a UIImage into a RGBAImage and vice versa.

This is my created class:

import UIKit


let image = UIImage(named: "sample")!






class imageFilter{


    func increaseContrast(image: UIImage) -> UIImage{
        let rgbaImage = RGBAImage(image: image)!
        var totalRed = 0
        var totalGreen = 0
        var totalBlue = 0
        let pixelCount = rgbaImage.width * rgbaImage.height

        for y in 0..<rgbaImage.height {
            for x in 0..<rgbaImage.width {
                let index = y * rgbaImage.width + x
                let pixel = rgbaImage.pixels[index]
                totalRed += Int(pixel.red)
                totalGreen += Int(pixel.green)
                totalBlue += Int(pixel.blue)
            }
        }


        let avgRed = totalRed/pixelCount
        let avgGreen = totalGreen/pixelCount
        let avgBlue = totalBlue/pixelCount


        for y in 0..<rgbaImage.height {
            for x in 0..<rgbaImage.width {
                let index = y * rgbaImage.width + x
                var pixel = rgbaImage.pixels[index]
                let redDelta = Int(pixel.red) - avgRed
                let greenDelta = Int(pixel.green) - avgGreen
                let blueDelta = Int(pixel.blue) - avgBlue
                pixel.red = UInt8(max(min(255, avgRed + 2 * redDelta), 0))
                pixel.blue = UInt8(max(min(255, avgBlue + 2 * blueDelta), 0))
                pixel.green = UInt8(max(min(255, avgGreen + 2 * greenDelta), 0))
                rgbaImage.pixels[index] = pixel


                }
            }
        let finished = rgbaImage.toUIImage()!
        return (finished)
        }


}


let test = imageFilter.increaseContrast(image)

There's an error on the last line saying

Cannot convert value of type 'UImage' to expected argument type 'imageFilter'

Here is the RGBA class :

import UIKit

 public struct Pixel {
    public var value: UInt32

public var red: UInt8 {
    get {
        return UInt8(value & 0xFF)
    }
    set {
        value = UInt32(newValue) | (value & 0xFFFFFF00)
    }
}

public var green: UInt8 {
    get {
        return UInt8((value >> 8) & 0xFF)
    }
    set {
        value = (UInt32(newValue) << 8) | (value & 0xFFFF00FF)
    }
}

public var blue: UInt8 {
    get {
        return UInt8((value >> 16) & 0xFF)
    }
    set {
        value = (UInt32(newValue) << 16) | (value & 0xFF00FFFF)
    }
}

public var alpha: UInt8 {
    get {
        return UInt8((value >> 24) & 0xFF)
    }
    set {
        value = (UInt32(newValue) << 24) | (value & 0x00FFFFFF)
    }
    }
}




public struct RGBAImage {
 public var pixels: UnsafeMutableBufferPointer<Pixel>

public var width: Int
public var height: Int

public init?(image: UIImage) {
    guard let cgImage = image.CGImage else { return nil }

    // Redraw image for correct pixel format
    let colorSpace = CGColorSpaceCreateDeviceRGB()

    var bitmapInfo: UInt32 = CGBitmapInfo.ByteOrder32Big.rawValue
    bitmapInfo |= CGImageAlphaInfo.PremultipliedLast.rawValue & CGBitmapInfo.AlphaInfoMask.rawValue

    width = Int(image.size.width)
    height = Int(image.size.height)
    let bytesPerRow = width * 4

    let imageData = UnsafeMutablePointer<Pixel>.alloc(width * height)

    guard let imageContext = CGBitmapContextCreate(imageData, width, height, 8, bytesPerRow, colorSpace, bitmapInfo) else { return nil }
    CGContextDrawImage(imageContext, CGRect(origin: CGPointZero, size: image.size), cgImage)

    pixels = UnsafeMutableBufferPointer<Pixel>(start: imageData, count: width * height)
}

public func toUIImage() -> UIImage? {
    let colorSpace = CGColorSpaceCreateDeviceRGB()
    var bitmapInfo: UInt32 = CGBitmapInfo.ByteOrder32Big.rawValue
    bitmapInfo |= CGImageAlphaInfo.PremultipliedLast.rawValue & CGBitmapInfo.AlphaInfoMask.rawValue

    let bytesPerRow = width * 4

    let imageContext = CGBitmapContextCreateWithData(pixels.baseAddress, width, height, 8, bytesPerRow, colorSpace, bitmapInfo, nil, nil)

    guard let cgImage = CGBitmapContextCreateImage(imageContext) else {return nil}
    let image = UIImage(CGImage: cgImage)

    return image
}
}

Answer 1

I am very sure that your problem is that you have not created an instance of your class while trying to call its member method.

Replace the last line with this code:

let test = imageFilter()
let processedImg = test.increaseContrast(image)