CGContext & CGMutablePath drawing line But it's be reversed - ios

Question

I use CgContext & CGMutablePath to Draw objects but the image that drawed be reversed.
I need Draw Object to CoreMl drawing classification project.
I use Touchs events to draw object
But when I draw to top direction if will be to bottom direction.
I want the line is correct direction
I learn from link
func drawContextLine(from fromPoint: CGPoint, to toPoint:CGPoint) ->CGImage?{
let grayscale = CGColorSpaceCreateDeviceGray()
if contextDraw == nil{
contextDraw = CGContext(
data:nil, width:256, height:256, bitsPerComponent:8, bytesPerRow:0,
space:grayscale, bitmapInfo:CGImageAlphaInfo.none.rawValue)
}
// intermediate_bitmap_context?.setStrokeColor(
// red: 1.0, green: 1.0, blue: 1.0, alpha: 1.0)
contextDraw?.setStrokeColor(UIColor.white.cgColor)
let path = CGMutablePath()
path.move(to: fromPoint)
path.addLine(to: toPoint)
contextDraw?.setLineWidth(5.0)
contextDraw?.beginPath()
contextDraw?.addPath(path)
contextDraw?.strokePath()
guard let imgCg = contextDraw?.makeImage() else {
return nil
}
imgViewPridict.image = UIImage.init(cgImage: imgCg)
return contextDraw?.makeImage()
}
touch begin
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first{
lastPoint = touch.location(in: self.view)
}
}
touch move
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
guard touches.first != nil else {
return
}
if let touch = touches.first {
let currentPoint = touch.location(in: self.view)
drawLine(from: lastPoint, to: currentPoint)
drawContextLine(from: lastPoint, to: currentPoint)
lastPoint = currentPoint
}
}

Answer 1

Try the code snippet below.
func drawContextLine(from fromPoint: CGPoint, to toPoint:CGPoint) ->CGImage?{
let grayscale = CGColorSpaceCreateDeviceGray()
if contextDraw == nil{
contextDraw = CGContext(
data:nil, width:256, height:256, bitsPerComponent:8, bytesPerRow:0,
space:grayscale, bitmapInfo:CGImageAlphaInfo.none.rawValue)
}
contextDraw?.setStrokeColor(UIColor.white.cgColor)
contextDraw?.saveGState()
contextDraw?.translateBy(x: 0, y: CGFloat(integerLiteral: contextDraw?.height ?? 0))
contextDraw?.scaleBy(x: 1.0, y: -1.0)
contextDraw?.setLineWidth(5.0)
contextDraw?.move(to: CGPoint(x: 100, y: 100))
contextDraw?.addLine(to: CGPoint(x: 150, y: 150))
contextDraw?.strokePath()
contextDraw?.restoreGState()
guard let imgCg = contextDraw?.makeImage() else {
return nil
}
imgViewPridict.image = UIImage.init(cgImage: imgCg)
return contextDraw?.makeImage()
}
You may need to inverse the content drawn on cgContext by applying AffineTransform to it.