How can i convert NSBezierPath to CGPath

Question

How can i convert between NSBezierPath to CGPath.

Thanks.

I don't see how this is a duplicate of that question. That's asking about how to stuff a CGPath into an archive or otherwise serialize it; this is about converting from one kind of path object to another, without necessarily serializing from one and deserializing to the other. — Peter Hosey, Feb 10 '13 at 01:34
I like this one, a library that adds UIKit functionality to the MacOS. Once included, you can set and read the `CGPath` for a `NSBezierPath` https://github.com/iccir/XUIKit — Wizard of Kneup, Dec 20 '13 at 08:14

score 43 · Accepted Answer · edited Feb 28 '18 at 09:40

Right from Apple documentation: Creating a CGPathRef From an NSBezierPath Object

Here is the relevant code.

@implementation NSBezierPath (BezierPathQuartzUtilities)
// This method works only in OS X v10.2 and later.
- (CGPathRef)quartzPath
{
    int i, numElements;

    // Need to begin a path here.
    CGPathRef           immutablePath = NULL;

    // Then draw the path elements.
    numElements = [self elementCount];
    if (numElements > 0)
    {
        CGMutablePathRef    path = CGPathCreateMutable();
        NSPoint             points[3];
        BOOL                didClosePath = YES;

        for (i = 0; i < numElements; i++)
        {
            switch ([self elementAtIndex:i associatedPoints:points])
            {
                case NSMoveToBezierPathElement:
                    CGPathMoveToPoint(path, NULL, points[0].x, points[0].y);
                    break;

                case NSLineToBezierPathElement:
                    CGPathAddLineToPoint(path, NULL, points[0].x, points[0].y);
                    didClosePath = NO;
                    break;

                case NSCurveToBezierPathElement:
                    CGPathAddCurveToPoint(path, NULL, points[0].x, points[0].y,
                                        points[1].x, points[1].y,
                                        points[2].x, points[2].y);
                    didClosePath = NO;
                    break;

                case NSClosePathBezierPathElement:
                    CGPathCloseSubpath(path);
                    didClosePath = YES;
                    break;
            }
        }

        // Be sure the path is closed or Quartz may not do valid hit detection.
        if (!didClosePath)
            CGPathCloseSubpath(path);

        immutablePath = CGPathCreateCopy(path);
        CGPathRelease(path);
    }

    return immutablePath;
}
@end

Bug Reporter

rdar://15758302: NSBezierPath to CGPath.

I think it's quite amazing that Apple puts that code in the docs instead of just adding a `CGPath` accessor to `NSBezierPath`. — , Mar 05 '16 at 10:20

score 34 · Answer 2 · edited Feb 04 '21 at 08:36

The syntax in Xcode 8 GM has been further simplified, code modified from rob-mayoff's answer above. Using this and a helper for addLine(to point: CGPoint) I am sharing drawing code cross platform.

extension NSBezierPath {

    public var cgPath: CGPath {
        let path = CGMutablePath()
        var points = [CGPoint](repeating: .zero, count: 3)

        for i in 0 ..< elementCount {
            let type = element(at: i, associatedPoints: &points)
            switch type {
            case .moveTo:
                path.move(to: points[0])
            case .lineTo:
                path.addLine(to: points[0])
            case .curveTo:
                path.addCurve(to: points[2], control1: points[0], control2: points[1])
            case .closePath:
                path.closeSubpath()
            @unknown default:
                continue
            }
        }

        return path
    }
}

rob mayoff · Answer 3 · 2018-03-31T21:18:46.447

19

This works in Swift 3.1 and later:

import AppKit

public extension NSBezierPath {

    public var cgPath: CGPath {
        let path = CGMutablePath()
        var points = [CGPoint](repeating: .zero, count: 3)
        for i in 0 ..< self.elementCount {
            let type = self.element(at: i, associatedPoints: &points)
            switch type {
            case .moveToBezierPathElement: path.move(to: points[0])
            case .lineToBezierPathElement: path.addLine(to: points[0])
            case .curveToBezierPathElement: path.addCurve(to: points[2], control1: points[0], control2: points[1])
            case .closePathBezierPathElement: path.closeSubpath()
            }
        }
        return path
    }

}

edited Mar 31 '18 at 21:18

answered Aug 09 '16 at 21:15

rob mayoff

375,296
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There are no such things as moveTo or addLineTo in Swift 3, are they? – El Tomato Mar 18 '17 at 23:28
This would be nicer as a convenience initializer on `CGPath`, so one could use the more-standard `CGPath(from: bezierPath)` syntax – Ky - Dec 04 '17 at 16:27
1

`NSColor` has a `cgColor` property, `NSGraphicsContext` has a `cgContext` property, and `NSColorSpace` has a `cgColorSpace` property. `NSImage` has ` cgImage(forProposedRect:context:hints:)` method. – rob mayoff Dec 04 '17 at 17:42
Also, Swift does not support convenience initializers on `CGPath`. If you try to declare one, you get the error “Convenience initializers are not supported in extensions of CF types”. – rob mayoff May 29 '19 at 21:20

Yura Voevodin · Answer 4 · 2019-05-06T14:27:02.253

For macOS better use - CGMutablePath

But, if you want cgPath for NSBezierPath:

Swift 5.0

extension NSBezierPath {

  var cgPath: CGPath {
    let path = CGMutablePath()
    var points = [CGPoint](repeating: .zero, count: 3)
    for i in 0 ..< self.elementCount {
      let type = self.element(at: i, associatedPoints: &points)

      switch type {
      case .moveTo:
        path.move(to: points[0])

      case .lineTo:
        path.addLine(to: points[0])

      case .curveTo:
        path.addCurve(to: points[2], control1: points[0], control2: points[1])

      case .closePath:
        path.closeSubpath()

      @unknown default:
        break
      }
    }
    return path
  }
}

score 7 · Answer 5 · answered Jan 06 '16 at 14:57

Here is a Swift version if anyone else finds a need for it:

extension IXBezierPath {
// Adapted from : https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CocoaDrawingGuide/Paths/Paths.html#//apple_ref/doc/uid/TP40003290-CH206-SW2
// See also: http://www.dreamincode.net/forums/topic/370959-nsbezierpath-to-cgpathref-in-swift/
func CGPath(forceClose forceClose:Bool) -> CGPathRef? {
    var cgPath:CGPathRef? = nil

    let numElements = self.elementCount
    if numElements > 0 {
        let newPath = CGPathCreateMutable()
        let points = NSPointArray.alloc(3)
        var bDidClosePath:Bool = true

        for i in 0 ..< numElements {

            switch elementAtIndex(i, associatedPoints:points) {

            case NSBezierPathElement.MoveToBezierPathElement:
                CGPathMoveToPoint(newPath, nil, points[0].x, points[0].y )

            case NSBezierPathElement.LineToBezierPathElement:
                CGPathAddLineToPoint(newPath, nil, points[0].x, points[0].y )
                bDidClosePath = false

            case NSBezierPathElement.CurveToBezierPathElement:
                CGPathAddCurveToPoint(newPath, nil, points[0].x, points[0].y, points[1].x, points[1].y, points[2].x, points[2].y )
                bDidClosePath = false

            case NSBezierPathElement.ClosePathBezierPathElement:
                CGPathCloseSubpath(newPath)
                bDidClosePath = true
            }

            if forceClose && !bDidClosePath {
                CGPathCloseSubpath(newPath)
            }
        }
        cgPath = CGPathCreateCopy(newPath)
    }
    return cgPath
}

score 5 · Answer 6 · answered Feb 07 '17 at 15:46

I can't figure out why the accepted answer adds some sophisticated close-path logic (maybe it is needed under some circumstances), but for those who just need a pristine conversion of the path, here is cleaned version of that code, implemented as a regular method:

- (CGMutablePathRef)CGPathFromPath:(NSBezierPath *)path
{
    CGMutablePathRef cgPath = CGPathCreateMutable();
    NSInteger n = [path elementCount];

    for (NSInteger i = 0; i < n; i++) {
        NSPoint ps[3];
        switch ([path elementAtIndex:i associatedPoints:ps]) {
            case NSMoveToBezierPathElement: {
                CGPathMoveToPoint(cgPath, NULL, ps[0].x, ps[0].y);
                break;
            }
            case NSLineToBezierPathElement: {
                CGPathAddLineToPoint(cgPath, NULL, ps[0].x, ps[0].y);
                break;
            }
            case NSCurveToBezierPathElement: {
                CGPathAddCurveToPoint(cgPath, NULL, ps[0].x, ps[0].y, ps[1].x, ps[1].y, ps[2].x, ps[2].y);
                break;
            }
            case NSClosePathBezierPathElement: {
                CGPathCloseSubpath(cgPath);
                break;
            }
            default: NSAssert(0, @"Invalid NSBezierPathElement");
        }
    }
    return cgPath;
}

Btw, I needed this to implement "NSBezierPath stroke contains point" method.

I've looked for this conversion to call CGPathCreateCopyByStrokingPath(), that converts NSBezierPath stroke outline to regular path, so you can test hits on strokes too, and here is the solution:

// stroke (0,0) to (10,0) width 5 --> rect (0, -2.5) (10 x 5)
NSBezierPath *path = [[NSBezierPath alloc] init];
[path moveToPoint:NSMakePoint(0.0, 0.0)];
[path lineToPoint:NSMakePoint(10.0, 0.0)];
[path setLineWidth:5.0];

CGMutablePathRef cgPath = [self CGPathFromPath:path];
CGPathRef strokePath = CGPathCreateCopyByStrokingPath(cgPath, NULL, [path lineWidth], [path lineCapStyle],
                                                      [path lineJoinStyle], [path miterLimit]);
CGPathRelease(cgPath);

NSLog(@"%@", NSStringFromRect(NSRectFromCGRect(CGPathGetBoundingBox(strokePath))));
// {{0, -2.5}, {10, 5}}

CGPoint point = CGPointMake(1.0, 1.0);
BOOL hit = CGPathContainsPoint(strokePath, NULL, point, (bool)[path windingRule]);

NSLog(@"%@: %@", NSStringFromPoint(NSPointFromCGPoint(point)), (hit ? @"yes" : @"no"));
// {1, 1}: yes

CGPathRelease(strokePath);

This is similar to QPainterPathStroker from Qt, but for NSBezierPath.

score 2 · Answer 7 · answered Jun 02 '20 at 21:44

c# Xamarin

        private CGPath convertNSBezierPathToCGPath(NSBezierPath sourcePath)
    {
        CGPath destinationPath = new CGPath();

        int i, numElements;

        // Then draw the path elements.
        numElements = (int)Convert.ToInt64(sourcePath.ElementCount);

        if (numElements > 0)
        {

            CGPath path = new CGPath();
            CGPoint[] points;
            bool didClosePath = true;

            for (i = 0; i < numElements; i++)
            {
                switch (sourcePath.ElementAt(i, out points))
                {
                    case NSBezierPathElement.MoveTo:
                        path.MoveToPoint(points[0]);
                        break;


                    case NSBezierPathElement.LineTo:
                        path.MoveToPoint(points[0]);
                        didClosePath = false;
                        break;

                    case NSBezierPathElement.CurveTo:
                        path.AddCurveToPoint(cp1: points[0], cp2: points[1], points[2]);
                        didClosePath = false;
                        break;

                    case NSBezierPathElement.ClosePath:
                        path.CloseSubpath();
                        didClosePath = true;
                        break;
                }
            }

            if (!didClosePath)
                path.CloseSubpath();

            destinationPath = new CGPath(path);

        }

        return destinationPath;

}

How can i convert NSBezierPath to CGPath

7 Answers7

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