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Hello I am very new to swift. I am trying to create a program that takes a UIImage and loops through it checking each pixel's RGB values to see if they are equal to a certain range of colors. I have a little experience in Java, but not much in swift. I have already made the program in Java. I have tried to replicate it in swift playground below. There are some comments to try to explain what my pseudo code intends.

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

import UIKit



// create constant that is the image
let profilePicture = UIImage(named: "meal1.jpg")


//loop through every pixel of that image and pass the specific pixel value into the function getPixelColor
for yCo in 0 ..< Int(profilePicture.size.height) {
    for xCo in 0 ..< Int(profilePicture.size.width) {
        profilePicture.getPixelColor(pos: CGPoint(x: xCo, y: yCo))
    }
}

//This function takes a specific pixel, gets the pixels red, green, and blue value and then checks to see if these value fall within a certain range of colors. The function itself I found on another stackoverflow question. I inserted the if statement at the end of it.

func getPixelColor(pos: CGPoint) -> UIColor {

    int allPixelCounter = 0
    int specificPixelColorsCounter = 0
    let pixelData = CGDataProviderCopyData(CGImageGetDataProvider(self.CGImage))
    let data: UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)

    let pixelInfo: Int = ((Int(self.size.width) * Int(pos.y)) + Int(pos.x)) * 4

    var red = CGFloat(data[pixelInfo]) / CGFloat(255.0)
    var green = CGFloat(data[pixelInfo+1]) / CGFloat(255.0)
    var blue = CGFloat(data[pixelInfo+2]) / CGFloat(255.0)
    //let a = CGFloat(data[pixelInfo+3]) / CGFloat(255.0)

    if red <= 130 && green >= 110 && blue <= 120 {
        specificPixelColorsCounter = specificPixelColorsCounter + 1
        //code to set this pixel to be white
    } else {
        allPixelCounter = allPixelCounter +1
        //code to set this pixel to be black
    }

}

//Function to display the image again with the pixels all either black or white now that for loop has finished to see what pixels were changed.

I would really appreciate anyone who could help me make this code workable. Any edits and advice is appreciated. Thank you very much!

Learning Programmer
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  • The challenge with just getting the data provider of an image is that there are a whole bunch of different image formats with radically different layouts. So in [Technical Q&A 1509](https://developer.apple.com/library/content/qa/qa1509/_index.html), Apple suggests creating a new context of a predefined format, draw the image into that context, and then you can access/manipulate it as outlined in https://stackoverflow.com/a/31661519/1271826. – Rob Sep 05 '17 at 14:52
  • There is another question posted similar to yours, and I think that the answer in it will do the trick for you. Here is the link. https://stackoverflow.com/questions/31661023/change-color-of-certain-pixels-in-a-uiimage Good luck – JustAnotherGuy Mar 22 '18 at 16:57

0 Answers0