ios - ImageView 上的平滑线条

Question

我目前在 Xcode 中有一个项目允许用户在 ImageView 上绘图，它运行良好，我唯一的问题是绘制的线条不清晰并且非常模糊和僵硬。我试图实现一些我在周围看到的想法，但它们都在我无法工作的更旧版本的 swift 中。

Screenshot of the blury lines

import Foundation
import UIKit

class SecondViewController: UIViewController {


    @IBOutlet weak var toolicon: UIButton!
    @IBOutlet var imageView: UIImageView!


    var lastPoint = CGPoint.zero
    var swiped = false
    var red:CGFloat = 0.00
    var green:CGFloat = 0.00
    var blue:CGFloat = 0.00
    var alpha:CGFloat = 1
    var lw:CGFloat = 2.5
    var tool:UIImageView!
    var isDrawing = true
    override func viewDidLoad() {
        super.viewDidLoad()

        tool = UIImageView()
        tool.frame = CGRect(x: self.view.bounds.size.width, y: self.view.bounds.height, width: 75, height: 75)
        tool.image = #imageLiteral(resourceName: "blank")
        self.view.addSubview(tool)
    }

    @IBAction func eraser(_ sender: AnyObject) {
        if (isDrawing) {
            (red,green,blue) = (1,1,1)
            tool.image = #imageLiteral(resourceName: "eraser2")
            toolicon.setImage(#imageLiteral(resourceName: "pen"), for: .normal)
            (lw) = (50)


        } else {
            (red,green,blue) = (0,0,0)
            tool.image = #imageLiteral(resourceName: "blank")
            toolicon.setImage(#imageLiteral(resourceName: "eraser"), for: .normal)
            (lw) = (2.5)
        }

        isDrawing = !isDrawing
    }

    func delay(_ delay:Double, closure:@escaping ()->()) {
        let when = DispatchTime.now() + delay
        DispatchQueue.main.asyncAfter(deadline: when, execute: closure)
    }

    @IBAction func save(_ sender: AnyObject) {
        if let image = imageView.image {
            UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
            self.imageView.image = nil

            // the alert view
            let alert = UIAlertController(title: "", message: "Thank you, your guestbook entry has been saved. Redirecting you the home page", preferredStyle: .alert)
            self.present(alert, animated: true, completion: nil)

            // change to desired number of seconds (in this case 5 seconds)
            let when = DispatchTime.now() + 2.5
            DispatchQueue.main.asyncAfter(deadline: when){
                // your code with delay
                alert.dismiss(animated: true, completion: nil)

            }
            delay(3.0) {
                // do stuff
                self.performSegue(withIdentifier: "savetocam", sender: nil)
            }
        }
    }
    @IBAction func lineSize(_ sender: AnyObject) {
        if sender.tag == 8 {
            (lw) = (1)
        } else if sender.tag == 9 {
            (lw) = (2.5)
        } else if sender.tag == 10 {
            (lw) = (5)
        }
    }


    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        swiped = false
        if let touch = touches.first  {
            lastPoint = touch.preciseLocation(in: self.view)
        }
    }

    @IBAction func colorsPicked(_ sender: AnyObject) {
        if sender.tag == 0 {
            (red,green,blue) = (0,0,0)
        } else if sender.tag == 1 {
            (red,green,blue) = (0.25,0.00,0.39)
        } else if sender.tag == 2 {
            (red,green,blue) = (0.65,0.62,0.75)
        } else if sender.tag == 3 {
            (red,green,blue) = (1.00,0.00,0.00)
        } else if sender.tag == 4 {
            (red,green,blue) = (0.49,0.77,0.46)
        } else if sender.tag == 5 {
            (red,green,blue) = (0.0,0.68,0.94)
        } else if sender.tag == 6 {
            (red,green,blue) = (0.96,0.56,0.34)
        } else if sender.tag == 7 {
            (red,green,blue) = (1.00,0.95,0.00)
        }
    }



    @IBAction func reset(_ sender: AnyObject) {
        self.imageView.image = nil
    }


    func drawLines(fromPoint:CGPoint,toPoint:CGPoint) {

        UIGraphicsBeginImageContext(self.view.frame.size)
        imageView.image?.draw(in: CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
        let context = UIGraphicsGetCurrentContext()

        context?.move(to:CGPoint(x: fromPoint.x, y: fromPoint.y))
        context?.addLine(to: CGPoint(x: toPoint.x, y: toPoint.y))

        if(isDrawing){
            context?.setBlendMode(CGBlendMode.normal)
        }
        else{
            context?.setBlendMode(CGBlendMode.clear)
        }

        tool.center = toPoint
        context?.setLineCap(CGLineCap.round)
        context?.setLineWidth(lw)
        context?.setStrokeColor(UIColor(red: red, green: green, blue: blue, alpha: alpha).cgColor)

        context?.strokePath()

        imageView.image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
    }

    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        swiped = true
        if let touch = touches.first {
            let currentPoint = touch.preciseLocation(in: self.view)
            drawLines(fromPoint: lastPoint, toPoint: currentPoint)

            lastPoint = currentPoint
        }
    }

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        if !swiped {
            drawLines(fromPoint: lastPoint, toPoint: lastPoint)
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }


}

Answer 1

您应该按如下方式设置您的 Core Graphics 上下文:

func drawLines(fromPoint:CGPoint,toPoint:CGPoint) {

    //UIGraphicsBeginImageContext(self.view.frame.size)
    UIGraphicsBeginImageContextWithOptions(self.view.frame.size, false, 0.0) //SET OPAQUENESS TO FALSE
    imageView.image?.draw(in: CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
    let context = UIGraphicsGetCurrentContext()

    context?.move(to:CGPoint(x: fromPoint.x, y: fromPoint.y))
    context?.addLine(to: CGPoint(x: toPoint.x, y: toPoint.y))

    if(isDrawing){
        context?.setBlendMode(CGBlendMode.normal)
    }
    else{
        context?.setBlendMode(CGBlendMode.clear)
    }

    tool.center = toPoint
    context?.setShouldAntialias(true) //IF YOU TURN THIS TO FALSE YOU GET RID OF BLURRING BUT LINES MAY BE A BIT JIGGY
    context?.interpolationQuality = .high //THIS MAKES LINES SMOOTHER
    context?.setLineCap(CGLineCap.round)
    context?.setFlatness(0.5)
    context?.setMiterLimit(0.5) //Play around with this value it should smoothen the angled parts of the signatures.
    context?.setLineWidth(lw)
    context?.setStrokeColor(UIColor(red: red, green: green, blue: blue, alpha: alpha).cgColor)
    context?.strokePath()

    imageView.image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
}

另请查看其他可能也有帮助的设置: Apple Docs