如何在普通的UIView(不是UIImage)上获得乘法混合模式 [英] How to get multiply blend mode on a plain UIView (not UIImage)

问题描述

我的iPad应用程序中有一个图像，我基本上想在其顶部放置一个滤色器.为此，我有一个彩色的UIView，它被遮罩为覆盖图像的特定形状.由于调整Alpha并不能达到我想要的效果，因此我想使用混合模式.

I have an image in my iPad app and I basically want to place a color filter on top of it. For this I have a colored UIView that is masked to a certain shape that I put over the image. Since adjusting the alpha isn't giving me the desired effect I'd like to use blend modes instead.

据我所知，您只能在图像上使用混合模式，而不能在普通视图上使用.视图的颜色是动态的，所以我不能只使用图片.

As far as I know you can only use blend modes on images and not plain views. The color of the view is dynamic so I can't just use a picture instead.

我还尝试将视图栅格化为图像，但是像素和奇数之类的东西都出现了，但是也许我做错了.

I also tried rasterizing the view to an image, but that got all pixely and odd or something, but maybe I did something wrong.

因此，基本问题是:是否可以将混合模式应用于视图?还是应该采用完全不同的方法来达到相同的目标?

So, the basic question is: Is it possible to apply blend modes to views? Or should I take a completely different approach to reach the same goal?

推荐答案

看看CALayer的compositingFilter的文档:

Take a look at the docs for CALayer's compositingFilter: https://developer.apple.com/documentation/quartzcore/calayer/1410748-compositingfilter

在颜色叠加视图上，您​​可以将view.layer.compositingFilter设置为替换为您自己的图像进行测试)

On your color overlay view you can set view.layer.compositingFilter to a CICategoryCompositeOperation to achieve blending with the content behind it. Here is some sample playground code with a multiply blend mode applied to test it out (replace the UIImage(named: "") with your own image for testing)

import UIKit
import PlaygroundSupport

class MyViewController : UIViewController {
    override func loadView() {

        let mainView = UIView()
        self.view = mainView

        let image = UIImageView()
        image.translatesAutoresizingMaskIntoConstraints = false;
        image.image = UIImage(named: "maxresdefault.jpg")
        mainView.addSubview(image)

        let overlay = UIView()
        overlay.translatesAutoresizingMaskIntoConstraints = false;
        overlay.backgroundColor = .red
        overlay.layer.compositingFilter = "multiplyBlendMode"
        mainView.addSubview(overlay)

        mainView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-0-[subview]-0-|", options: .directionLeadingToTrailing, metrics: nil, views: ["subview": view]))
        mainView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-0-[subview]-0-|", options: .directionLeadingToTrailing, metrics: nil, views: ["subview": view]))

        mainView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|-0-[subview]-0-|", options: .directionLeadingToTrailing, metrics: nil, views: ["subview": overlay]))
        mainView.addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|-0-[subview]-0-|", options: .directionLeadingToTrailing, metrics: nil, views: ["subview": overlay]))
    }
}

PlaygroundPage.current.liveView = MyViewController()

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