How do I get the color of a pixel in a UIImage?

Question

So I'm trying to make a program where Im taking a photo and it tells the user what the color is. I'm having trouble implementing the portion of func getPixelColor. Could anyone give me some tips on how to fuse this program together?

import UIKit

class ViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

@IBOutlet weak var cameraButton: UIButton!
@IBOutlet weak var cameraView: UIImageView!
@IBOutlet weak var photosButton: UIButton!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
}

@IBAction func tappedCameraButton(_ sender: Any) {
    let picker = UIImagePickerController()
    picker.sourceType = .camera
    picker.allowsEditing = true
    picker.delegate = self
    present(picker, animated: true)
}

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
    
    cameraView?.image = info[UIImagePickerController.InfoKey.editedImage] as? UIImage
    picker.dismiss(animated: true, completion: nil)
}
extension UIImage {
    func getPixelColor(pos: CGPoint) -> UIColor {

        let pixelData = self.cgImage!.dataProvider!.data
        let data: UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)

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

        let r = CGFloat(data[pixelInfo]) / CGFloat(255.0)
        let g = CGFloat(data[pixelInfo+1]) / CGFloat(255.0)
        let b = CGFloat(data[pixelInfo+2]) / CGFloat(255.0)
        let a = CGFloat(data[pixelInfo+3]) / CGFloat(255.0)

        return UIColor(red: r, green: g, blue: b, alpha: a)
    }

}

}

}

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score 1 · Answer 1 · answered Jan 06 '21 at 01:05

1

You need to get the CGPoint of the user touch and then use getPixelColor(pos:) to get the color.

There are two ways to get CGPoint

You can use any of the methods to get the location touchesBegan(_:with:), touchesMoved, touchesEnded
Use tap gesture

Here is the StackOverlow code the get the CGPoint: How to get a CGPoint from a tapped location?

answered Jan 06 '21 at 01:05

Inder Kumar Rathore

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you need to implement these methods in that vc where you're displaying the image – Inder Kumar Rathore Jan 06 '21 at 02:08

score 0 · Answer 2 · answered Jan 08 '21 at 04:24

extension UIImage {
     func getPixelColor(pos: CGPoint) -> UIColor? {
        
        guard let cgImg = cgImage, let provider = cgImg.dataProvider else {
            return nil
        }
        let pixelData = provider.data
        
        let data: UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)

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

        let r = CGFloat(data[pixelInfo]) / CGFloat(255.0)
        let g = CGFloat(data[pixelInfo+1]) / CGFloat(255.0)
        let b = CGFloat(data[pixelInfo+2]) / CGFloat(255.0)
        let a = CGFloat(data[pixelInfo+3]) / CGFloat(255.0)
        return UIColor(red: r, green: g, blue: b, alpha: a)
     }
 }

How do I get the color of a pixel in a UIImage?

2 Answers2