iOS/Swift：如何混合多个 UIView

Question

I'm trying to make a color dodge blend of an image with other UIView's (CollectionView, a background ImageView, ...). In Android, I can put some view over the others and then apply a BlendMode.COLOR_DODGE or PorterDuffXfermode(PorterDuff.Mode.ADD) to Paint when I'm drawing the bitmap over the canvas.

I tried making this work using the same analogy: putting an UIView over the others and applying the color dodge. I already tried:

override func draw(_ rect: CGRect) {
    self.image?.draw(in: rect, blendMode: .colorDodge, alpha: 1.0)
}

But I noticed that blendMode only works if I draw all the content of view inside of it's draw method and that behavior will not work for me.

There's some way to achieve blending of multiple views in iOS?

Answer 1

You can use compositingFilter :

view.layer.compositingFilter = "colorDodgeBlendMode"

Some other valid values:

"normalBlendMode" "darkenBlendMode" "multiplyBlendMode" "colorBurnBlendMode" "lightenBlendMode" "screenBlendMode" "colorDodgeBlendMode" "overlayBlendMode" "softLightBlendMode" "hardLightBlendMode" "differenceBlendMode" "exclusionBlendMode"