CODEWITHSUNDEEP
iosswiftcolorsuicolor
J.Treutlein
J.Treutlein

Reputation: 983

Swift 4: Get RGB values of pixel in UIImage

I know there have been lots of posts for how to get the colour of a pixel in a UIImage given a CGPoint but they are all outdated as far as I can tell. Most of them contain CGImageGetDataProvider and CGDataProviderCopyData which in Swift 4 is an error:

'CGImageGetDataProvider' has been replaced by property 'CGImage.dataProvider' 'CGDataProviderCopyData' has been replaced by property 'CGDataProvider.data'

Xcode suggests these substitutes, but they do not exist so I have been having trouble trying to recreate a Swift 4 function to get the colour of a pixel in a UIImage.

Here is the typical Swift 3 function:

extension UIImage {

    subscript (x: Int, y: Int) -> UIColor? {

        if x < 0 || x > Int(size.width) || y < 0 || y > Int(size.height) {
            return nil
        }

        let provider = CGImageGetDataProvider(self.cgImage!)
        let providerData = CGDataProviderCopyData(provider!)
        let data = CFDataGetBytePtr(providerData)

        let numberOfComponents = 4
        let pixelData = ((Int(size.width) * y) + x) * numberOfComponents

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

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

}

Any suggestions or comments are greatly appreciated. Thank you!

EDIT

I tried @Mukesh 's solution but even though all the build errors are fixed, the program crashes. It says:

The image I give to the function is not nil, I have checked.

P.S. The image I am using for the function is a snapshot of the camera. I have a live camera and after every frame, this function (below) is called where I turn the current frame into a UIImage. This UIImage is what I want to find the pixel colour of:

func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        let pixelBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
        let ciImg = CIImage(cvPixelBuffer: pixelBuffer)
        let cameraImage = UIImage(ciImage: ciImg)
        let col = cameraImage.getPixelColor(pos: CGPoint(x: 100, y: 100))
   }

I used CGPoint(x: 100, y: 100) to see if it crashed as an example, and it did. This point is also in the image because if it wasn't, it would have returned nil here:

if x < 0 || x > Int(size.width) || y < 0 || y > Int(size.height) {
            return nil
}

Is there a way to find out why it gets a nil value? Or maybe a different solution? Thank you :)

Upvotes: 6

Views: 7055

Answers (1)

Mukesh
Mukesh

Reputation: 2902

Here is the code I get after removing the errors:

extension UIImage {

    subscript (x: Int, y: Int) -> UIColor? {

        if x < 0 || x > Int(size.width) || y < 0 || y > Int(size.height) {
            return nil
        }

        let provider = self.cgImage!.dataProvider
        let providerData = provider!.data
        let data = CFDataGetBytePtr(providerData)

        let numberOfComponents = 4
        let pixelData = ((Int(size.width) * y) + x) * numberOfComponents

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

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

Upvotes: 3

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