instaFilter Processor错误-预期返回的函数中缺少返回

Question

I'm currently learning swift and I'm currently taking a class for it. We are told to write a code to apply filters to a sample picture to change a given intensity of a color on an image in its parameter and then return the modified image.

In the code that I have written, on the last couple lines, it states an error saying

missing return in a function expected to return 'UIImage'

my class code:

import UIKit


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

class brightnessFilter {

func increaseContrast(image: UIImage) -> UIImage{
    var rgbaImage = RGBAImage(image: image)!

    let avgRed = 118
    let avgGreen = 98
    let avgBlue = 83

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

        }
    }
    let newImage1 = rgbaImage.toUIImage()!
    return (newImage1)
  }

}

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


class redFilter {


func increaseContrast(image: UIImage) -> UIImage{
    var rgbaImage = RGBAImage(image: image)!

    let avgRed = 118

    for y in 0..<rgbaImage.height {
        for x in 0..<rgbaImage.width {
            let index = y * rgbaImage.width + x
            var pixel = rgbaImage.pixels[index]
            let redDiff = Int(pixel.red) - avgRed
            if (redDiff > 0) {
                pixel.red = UInt8( max(0, min(255, avgRed + redDiff * 5)))
                rgbaImage.pixels[index] = pixel
            }
        }
        let newImage2 = rgbaImage.toUIImage()!
        return (newImage2)
    }
  }
}

let test2 = redFilter()

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)
    }
  }
}

Answer 1

When a method declaration is written with return value, you must make sure it is always return a value.

I believe your error is in the following method:

func increaseContrast(image: UIImage) -> UIImage {
    var rgbaImage = RGBAImage(image: image)!

    let avgRed = 118
    let newImage2 = UIImage() //<-- Added         

    for y in 0..<rgbaImage.height {
        for x in 0..<rgbaImage.width {
            let index = y * rgbaImage.width + x
            var pixel = rgbaImage.pixels[index]
            let redDiff = Int(pixel.red) - avgRed
            if (redDiff > 0) {
                pixel.red = UInt8( max(0, min(255, avgRed + redDiff * 5)))
                rgbaImage.pixels[index] = pixel
            }
        }
        let newImage2 = rgbaImage.toUIImage()!
        return (newImage2) //<---NOTICE
    }// <---FIX
  }

Notice : that the return statement is in the for loop, meaning the method might not always return a value.

Fix : Put the return statement under the curly brackets marked in the code.

Added : You must return a value, therefore, you must create one

Side note: Make sure to handle nil