투명한 픽셀로 이미지를 그레이 스케일하여 모두 불투명하게 만드는 방법은 무엇입니까?

이미지의 투명한 부분을 흰색 (또는 다른 색상)으로 만들려면 그리기 컨텍스트에서 채워진 사각형을 그립니다.

스위프트 3 :

extension UIImage {
    func grayScaleImage() -> UIImage {
        //let imageRect = CGRectMake(0, 0, self.size.width, self.size.height);
        let imageRect = CGRect(origin: CGPoint.zero, size: self.size)
        let colorSpace = CGColorSpaceCreateDeviceGray();

        let width = Int(self.size.width)
        let height = Int(self.size.height)

        let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: .allZeros)

        // set Fill Color to White (or some other color)
        context?.setFillColor(UIColor.white.cgColor)
        // Draw a white-filled rectangle before drawing your image
        context?.fill(imageRect)

        context?.draw(self.cgImage!, in: imageRect)

        let imageRef = context?.makeImage()
        let newImage = UIImage(cgImage: imageRef!)
        return newImage
    }
}

스위프트 2.2 :

extension UIImage {
    func grayScaleImage() -> UIImage {
        let imageRect = CGRectMake(0, 0, self.size.width, self.size.height);
        let colorSpace = CGColorSpaceCreateDeviceGray();

        let width = Int(self.size.width)
        let height = Int(self.size.height)
        let context = CGBitmapContextCreate(nil, width, height, 8, 0, colorSpace, .allZeros);

        // set Fill Color to White (or some other color)
        CGContextSetFillColorWithColor(context, UIColor.whiteColor().CGColor)
        // Draw a white-filled rectangle before drawing your image
        CGContextFillRect(context, imageRect)

        CGContextDrawImage(context, imageRect, self.CGImage!);

        let imageRef = CGBitmapContextCreateImage(context);
        let newImage = UIImage(CGImage: imageRef!)
        return newImage
    }
}