How can i convert NSBezierPath to CGPath - cocoa

Question

How can i convert between NSBezierPath to CGPath.
Thanks.

Answer 1

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.

Answer 2

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
}
}

Answer 3

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
}
}

Answer 4

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
}
}

Answer 5

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
}

Answer 6

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.

Answer 7

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;
}