PorterDuff.mode in Swift to colorize an image

Question

Hi all,

I'm trying to move app from Android to iOS but I'm finding some difficulties with image transformation...

The app is about image filtering and I found all the equivalent codes for brightness, saturation, contrast, etc. ColorMatrix but I have problems trying to colorize the image.

In Android I used the next code:

public static Bitmap doNalaFilter (Bitmap src) {
  Bitmap bmBrown0 = Bitmap.createBitmap(src.getWidth(), src.getHeight(), src.getConfig());
  Canvas cBrown0 = new Canvas(bmBrown0);
  Paint paintBrown0 = new Paint();
  paintBrown0.setColorFilter(new LightingColorFilter(Color.WHITE, 0x800000));
  cBrown0.drawBitmap(src, 0, 0, paintBrown0);
  Bitmap bmBrown = Bitmap.createBitmap(src.getWidth(), src.getHeight(), src.getConfig());
  Canvas cBrown = new Canvas(bmBrown);
  cBrown.drawBitmap(src, 0, 0, null);
  Paint paintBrown = new Paint();
  paintBrown.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY));
  cBrown.drawBitmap(bmBrown0, 0, 0, paintBrown);
  return bmBrown;
}

Which results in a new image with high brown tones.

In Swift I'm trying the next code:

func nalaFilter() -> UIImage? {
  let inImage = CIImage (image: self)
  let SRGBImage = inImage?.applyingFilter("CILinearToSRGBToneCurve")

  dynamic let brownMatrix = CIFilter (name: "CIMultiplyBlendMode")

  let brownRect = CGRect (
  x: (SRGBImage?.extent.origin.x)!,
  y: (SRGBImage?.extent.origin.y)!,
  width: (SRGBImage?.extent.size.width)!,
  height: (SRGBImage?.extent.size.height)!)
  let brownColor = CIColor (red: 128.0/255.0, green: 0.0, blue: 0.0)
  let brownOverlay = CIImage (color: brownColor)
  let brownCroppedImage = brownOverlay.cropped(to: brownRect)
  brownMatrix?.setValue(SRGBImage, forKey: kCIInputImageKey)
  brownMatrix?.setValue(brownCroppedImage, forKey: kCIInputBackgroundImageKey)
  let brownOutImage = brownMatrix?.outputImage

  let linearImage = brownOutImage?.applyingFilter("CISRGBToneCurveToLinear")

  let cgImage = CIContext().createCGImage(linearImage!, from: linearImage!.extent)
  return UIImage (cgImage: cgImage!)
}

Which results in the original image with like a really really dark brown crystal on it...

I can't find the equivalent code and it's so frustrating because I've tryed even all CICategoryCompositeOperation in my brownMatrix.

Thanks in advance!

Core Image

990

Posted by

SmiliPRO

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Answer 1

Finally I got the next code which solves my problem:

func nalaFilter() -> UIImage? {
  let brownColor = CIColor (red: 128.0/255.0, green: 0.0, blue: 0.0)
  let brownRect = CGRect (origin: .zero, size: self.size)

  //Colored image
  UIGraphicsBeginImageContextWithOptions(brownRect.size, true, 0.0)
  brownColor.setFill()
  UIRectFill(brownRect)
  let brownColoredImage = UIGraphicsGetImageFromCurrentImageContext()
  let brownContext = UIGraphicsGetCurrentContext()
  brownContext!.setFillColor(UIColor.white.cgColor)
  brownContext!.fill(brownRect)
  self.draw(in: brownRect, blendMode: .normal, alpha: 1)
  brownColoredImage?.draw(in: brownRect, blendMode: .colorDodge, alpha: 1)
  let outBrown0Image = UIGraphicsGetImageFromCurrentImageContext()

  //Multiplied image
  self.draw(in: brownRect, blendMode: .normal, alpha: 1)
  outBrown0Image?.draw(in: brownRect, blendMode: .multiply, alpha: 1)
  let outBrownImage = UIGraphicsGetImageFromCurrentImageContext()
  UIGraphicsEndImageContext()

  return outBrownImage
}

This gets exactly the same result than my Android one.

Posted by

SmiliPRO

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Answer 2

Finally I got the next code which solves my problem:

func nalaFilter() -> UIImage? {
  let brownColor = CIColor (red: 128.0/255.0, green: 0.0, blue: 0.0)
  let brownRect = CGRect (origin: .zero, size: self.size)

  //Colored image
  UIGraphicsBeginImageContextWithOptions(brownRect.size, true, 0.0)
  brownColor.setFill()
  UIRectFill(brownRect)
  let brownColoredImage = UIGraphicsGetImageFromCurrentImageContext()
  let brownContext = UIGraphicsGetCurrentContext()
  brownContext!.setFillColor(UIColor.white.cgColor)
  brownContext!.fill(brownRect)
  self.draw(in: brownRect, blendMode: .normal, alpha: 1)
  brownColoredImage?.draw(in: brownRect, blendMode: .colorDodge, alpha: 1)
  let outBrown0Image = UIGraphicsGetImageFromCurrentImageContext()

  //Multiplied image
  self.draw(in: brownRect, blendMode: .normal, alpha: 1)
  outBrown0Image?.draw(in: brownRect, blendMode: .multiply, alpha: 1)
  let outBrownImage = UIGraphicsGetImageFromCurrentImageContext()
  UIGraphicsEndImageContext()

  return outBrownImage
}

This gets exactly the same result than my Android one.

Posted by

SmiliPRO

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PorterDuff.mode in Swift to colorize an image

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