ScratchCard implementation inspect scratched area

ScratchCard-InspectImage.swift

extension UIView {
  
    func transparentPercentage() -> Double {
        let width = Int(bounds.width)
        let height = Int(bounds.height)

        // 1. Prepare a memory space where you write in RGBA data of the view
        var pixelData: [UInt8] = Array<UInt8>(repeating: 0, count: width * height * 4)
        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)

        // 2. Prepare a context with the RGB space you secured above
        guard let context = CGContext(data: &pixelData, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 4 * width, space: colorSpace, bitmapInfo: bitmapInfo.rawValue) else { return 0 }
 
        // 3. Render the entire view into the context, thereby filling in the `pixelData` variable
        self.layer.render(in: context)
        let totalArea = width * height
        var transparentCount = 0
        for x in 0 ..< width {
            for y in 0 ..< height {
                // 4. Get alpha component and see if it is zero.
                let alpha = pixelData[(y * width + x) * 4 + 3]
                if alpha == 0 {
                    transparentCount += 1
                }
            }
        }
        return Double(transparentCount) / Double(totalArea) * 100
    }
}