Image manipulation example in Swift demonstrating UIImage, RGBAImage,

image.swift

//: Playground - noun: a place where people can play

import UIKit

var str = "Hello, playground"
let image = UIImage(named: "demo.jpg")!

let myRGBA = RGBAImage(image: image)!

//
// Change the RGB values of a particular pixel 
//

// Pixel location
let x = 10
let y = 10

// Pixel index
let index = y * myRGBA.width + x

// Pixel itself
var pixel = myRGBA.pixels[index]

pixel.red
pixel.green
pixel.blue

pixel.red = 255
pixel.green = 0
pixel.blue = 0

myRGBA.pixels[index] = pixel

let newImage = myRGBA.toUIImage()

//
// Calculate the avarage RGB values of the image
//

/*
// RGB accumulator
var totalRed = 0
var totalGreen = 0
var totalBlue = 0

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

let count = myRGBA.width * myRGBA.height
let avgRed = totalRed / count
let avgGreen = totalGreen / count
let avgBlue = totalBlue / count
*/

//
// Amplify the red color
//

// Calculated RGB accumulator
let avgRed = 136
let avgGreen = 131
let avgBlue = 134

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

let newImage2 = myRGBA.toUIImage()