objective-c - iOS imageView渲染的问题

Question

比如说A是一个imageView，B仅仅是一个普通的透明的view，我希望A被B盖住的部分是彩色的，而没有盖住的部分是黑白的，请问有什么实现的思路吗

Answer 1

boleh mengawal layer.mask pelaksanaan A. Topeng ialah kawasan bertindih A dan B. Pengisian rect layer.mask boleh diubah dengan mengira path kawasan bertindih. Banyak kesan penyamaran dicapai menggunakan topeng.

Saya menulis kod untuk anda rujuk. Anda boleh melihat kesannya secara langsung di taman permainan:

import UIKit
import PlaygroundSupport

/// 可以拖动的View，即ViewB
class DragableView:UIView {
    var maskLayer: CAShapeLayer?
    var viewThatMask: UIView? {
        didSet {
            maskLayer?.removeFromSuperlayer()
            maskLayer = nil
            if let _ = viewThatMask {
                self.maskLayer = CAShapeLayer()
                self.maskLayer?.backgroundColor = UIColor.orange.cgColor
                self.maskLayer?.frame = self.bounds
                self.layer.mask = self.maskLayer
            }
        }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        self.isOpaque = true
        self.backgroundColor = .black
        
        let gesture = UIPanGestureRecognizer(target: self, action: #selector(self.panGestureEvent(_:)))
        self.addGestureRecognizer(gesture)
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    /// 相交部分改变的处理闭包， 参数rect是相交的区域， view是maskView
    var maskChangedHandler:((CGRect, UIView)->Void)?
    
    func panGestureEvent(_ gesture:UIPanGestureRecognizer) {
        let point = gesture.translation(in: self)
        if gesture.state == .changed {
            self.frame.origin.x += point.x
            self.frame.origin.y += point.y
            gesture.setTranslation(.zero, in: self)
            
            if let viewThatMask = self.viewThatMask,
                let superview = self.superview {
                // 两个View相交rect，以父view为参考
                let rectInSuper = self.frame.intersection(viewThatMask.frame)
                // 转化为以图片的坐标系的rect
                let interRectInMask = superview.convert(rectInSuper, to: viewThatMask)
                
                if let maskChangedHandler = self.maskChangedHandler {
                    maskChangedHandler(interRectInMask, viewThatMask)
                }
            }
        }
    }
}

let imageViewColorful = UIImageView(frame: CGRect(x:50, y:50, width:150, height:100))
imageViewColorful.image = UIImage(named: "dog_colorful")
imageViewColorful.layer.mask = CAShapeLayer()

let imageViewGray = UIImageView(frame: CGRect(x:50, y:50, width:150, height:100))
imageViewGray.image = UIImage(named: "dog_gray")


let dragView = DragableView(frame: CGRect(x:50, y:200, width:200, height:200))
dragView.viewThatMask = imageViewColorful
dragView.maskChangedHandler = { rect, viewA in
    if let maskLayer = viewA.layer.mask as? CAShapeLayer {
        maskLayer.path = CGPath(rect: rect, transform: nil)
        maskLayer.fillColor = UIColor.black.cgColor
    }
}

let view = UIView(frame: CGRect(x:0, y:0, width:400, height:640))
view.backgroundColor = .white

view.addSubview(dragView)
view.addSubview(imageViewGray)
view.addSubview(imageViewColorful)

PlaygroundPage.current.liveView = view

Jika ia berjalan seperti biasa, anda boleh melihat kesan berikut dalam Penolong Editor taman permainan:

Answer 2

1. Kira saiz persilangan AB
2 Kira titik permulaan bahagian berwarna
3 Gunakan lengkung Bezier untuk melukis bahagian berwarna
4 ke lengkung Bezier Langkah demi langkah ketiga, tambah lapisan pada A.

Fikiran peribadi saya, anda boleh mencubanya.