Question

我一直致力于使用swift 3.0在图像视图上绘制一条红线，并遇到了一些问题。正如你猜测的那样，我正在使用堆栈溢出中的一些代码来帮助我完成我的第一次初始尝试并得到一个奇怪的错误。

当我将手指拖过图像视图时，它确实绘制了一条红线，但对于每个＆＃34;框架＆＃34;它会丢掉我在屏幕上进一步绘制的所有内容。因此，当我绘制时，它看起来像我正在绘制的线条正在下降，然后完全离开屏幕。

我正在寻找的是能够简单地在图像视图上绘制，而不是在每个帧下移动的所有内容，我希望它保持在相同的位置，类似于它在所有绘图应用程序等上的工作方式

以下是所有代码：

@IBOutlet weak var mainImageView: UIImageView!
var lastPoint = CGPoint.zero
var fromPoint = CGPoint();
var toPoint = CGPoint.zero
var red: CGFloat = 255.0
var green: CGFloat = 0.0
var blue: CGFloat = 0.0
var brushWidth: CGFloat = 10.0
var opacity: CGFloat = 1.0
var swiped = false

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint)
{
    UIGraphicsBeginImageContextWithOptions(self.mainImageView.bounds.size, false, 0);
    mainImageView.image?.draw(in: CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height))
    let context = UIGraphicsGetCurrentContext()

    context?.move(to: fromPoint)
    context?.addLine(to: toPoint)
    context?.setLineCap(CGLineCap.round)
    context?.setLineWidth(brushWidth)
    context?.setStrokeColor(red: red, green: green, blue: blue, alpha: 1.0)
    context?.setBlendMode(CGBlendMode.normal)
    context?.strokePath()

    mainImageView.image = UIGraphicsGetImageFromCurrentImageContext()
    mainImageView.alpha = opacity
    UIGraphicsEndImageContext()

}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    swiped = false;
    if let touch = touches.first {
        lastPoint = touch.location(in: self.mainImageView)
    }
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    swiped = true;
    if let touch = touches.first {
        let currentPoint = touch.location(in: mainImageView)
        drawLineFrom(fromPoint: lastPoint, toPoint: currentPoint)
        lastPoint = currentPoint
    }
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    if(!swiped){
        self.drawLineFrom(fromPoint: lastPoint, toPoint: lastPoint)
    }
}

感谢帮助人员！

Answer 1

以下代码可以使用触摸

绘制图像

override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {


if let touch = touches.first as? UITouch{

    prevPoint1 = touch.previousLocationInView(self.view)

    prevPoint2 = touch.previousLocationInView(self.view)

    lastPoint = touch.locationInView(self.view)

}

}



 override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {


if let touch = touches.first as? UITouch{

    let currentPoint = touch.locationInView(view)



    prevPoint2 = prevPoint1

    prevPoint1 = touch.previousLocationInView(self.view)





    UIGraphicsBeginImageContext(view.frame.size)

    let context = UIGraphicsGetCurrentContext()

    TempImage.image?.drawInRect(CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height))



    var mid1 = CGPointMake((prevPoint1.x + prevPoint2.x)*0.5, (prevPoint1.y + prevPoint2.y)*0.5)

    var mid2 = CGPointMake((currentPoint.x + prevPoint1.x)*0.5, (currentPoint.y + prevPoint1.y)*0.5)



    CGContextMoveToPoint(context, mid1.x, mid1.y)

    CGContextAddQuadCurveToPoint(context, prevPoint1.x, prevPoint1.y, mid2.x, mid2.y)

    //CGContextAddLineToPoint(context, toPoint.x, toPoint.y)



    CGContextSetLineCap(context, kCGLineCapRound)

    CGContextSetLineWidth(context, brushWidth)

    CGContextSetRGBStrokeColor(context, red, green,blue, 1.0)

    CGContextSetBlendMode(context, kCGBlendModeNormal)



    CGContextStrokePath(context)



    TempImage.image = UIGraphicsGetImageFromCurrentImageContext()

    TempImage.alpha = opacity

    UIGraphicsEndImageContext()



    lastPoint = currentPoint

}

 }



 override func touchesEnded(touches: Set<NSObject>, withEvent event: UIEvent) {



UIGraphicsBeginImageContext(MainImage.frame.size)

MainImage.image?.drawInRect(CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height), blendMode: kCGBlendModeNormal, alpha: 1.0)

TempImage.image?.drawInRect(CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height), blendMode: kCGBlendModeNormal, alpha: opacity)

MainImage.image = UIGraphicsGetImageFromCurrentImageContext()

UIGraphicsEndImageContext()



TempImage.image = nil

}

Answer 2

以下代码可以使用touch（Swift 3.0）

绘制图像

func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) {
swiped = false
if let touch = touches.first as? UITouch {
    lastPoint = touch.location(in: self.view)
}
 }
 func drawLineFrom(fromPoint: CGPoint, toPoint: CGPoint) {

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


context?.move(to: fromPoint)
context?.addLine(to: toPoint)

context?.setLineCap(CGLineCap.round)
context?.setLineWidth(brushWidth)
context?.setStrokeColor(red: red, green: green, blue: blue, alpha: 1.0)
context?.setBlendMode(CGBlendMode.normal)
context?.strokePath()


tempImageView.image = UIGraphicsGetImageFromCurrentImageContext()
tempImageView.alpha = opacity
UIGraphicsEndImageContext()

}

 func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
swiped = true
if let touch = touches.first as? UITouch {
    let currentPoint = touch.location(in: view)
    drawLineFrom(fromPoint: lastPoint, toPoint: currentPoint)

    lastPoint = currentPoint
}
}

Swift 3.0 - 用手指在imageView上绘图

2 个答案: