Converting a Quartz method from iOS to OSX

I have this quartz class that works fine on iOS and draws an orange pizza slice style graph over a gray circle and I am trying to convert it to cocoa.

+ (UIImage *)circleWithDiameter:(CGFloat) diameter color:(UIColor *)color progress:(CGFloat)progress { CGFloat radius = diameter/2.0f; CGFloat scale = [[UIScreen mainScreen] scale]; // we need to size the graphics context according to the device scale CGRect rect = CGRectMake(0.0f, 0.0f, diameter, diameter); UIGraphicsBeginImageContextWithOptions(rect.size, NO, scale); CGContextRef context = UIGraphicsGetCurrentContext(); // create a gray circle background CGContextSetLineWidth(context, 0); // set the line width CGContextSetFillColorWithColor(context, color.CGColor); CGContextBeginPath(context); CGContextAddEllipseInRect(context, rect); CGContextDrawPath(context, kCGPathFill); // Or kCGPathFill // Draw the slice CGFloat angle = progress * 2.0f * M_PI; CGPoint center = CGPointMake(radius, radius); CGContextBeginPath(context); CGContextMoveToPoint(context, center.x, center.y); CGPoint p1 = CGPointMake(center.x + radius * cosf(angle), center.y + radius * sinf(angle)); CGContextAddLineToPoint(context, p1.x, p1.y); CGContextMoveToPoint(context, center.x, center.y); CGContextAddArc(context, center.x, center.y, radius, 0.0f, angle, 0); CGContextClosePath(context); UIColor *orange = [UIColor orangeColor]; CGContextSetFillColorWithColor(context, orange.CGColor); CGContextDrawPath(context, kCGPathFill); UIImage *result = UIGraphicsGetImageFromCurrentImageContext(); CGContextRelease(context); return result; } 

This is the class I have converted to cocoa.

+ (NSImage *)circuloWithDiameter:(CGFloat)diameter color:(NSColor *)color progress:(CGFloat)progress { CGFloat radius = diameter/2.0f; CGContextRef context = [[NSGraphicsContext currentContext] graphicsPort]; // draw the gray circle background CGContextSetLineWidth(context, 0); // set the line width CGContextSetFillColorWithColor(context, color.CGColor); CGContextBeginPath(context); CGContextAddEllipseInRect(context, rect); CGContextDrawPath(context, kCGPathFill); // Or kCGPathFill // draw the orange slice CGFloat angle = progress * 2.0f * M_PI; CGPoint center = CGPointMake(radius, radius); CGContextBeginPath(context); CGContextMoveToPoint(context, center.x, center.y); CGPoint p1 = CGPointMake(center.x + radius * cosf(angle), center.y + radius * sinf(angle)); CGContextAddLineToPoint(context, p1.x, p1.y); CGContextMoveToPoint(context, center.x, center.y); CGContextAddArc(context, center.x, center.y, radius, 0.0f, angle, 0); CGContextClosePath(context); NSColor *orange = [NSColor orangeColor]; CGContextSetFillColorWithColor(context, orange.CGColor); CGContextDrawPath(context, kCGPathFill); CGImageRef imageRef = CGBitmapContextCreateImage(context); NSImage* result = [[NSImage alloc] initWithCGImage:imageRef size:NSMakeSize(diameter, diameter)]; CFRelease(imageRef); CGContextRelease(context); return result; } 

Apparently the conversion goes fine and Xcode is not whining about anything but when the cocoa version runs, it crashes on the line

 CGImageRef imageRef = CGBitmapContextCreateImage(context); 

with the message

<Error>: CGBitmapContextCreateImage: invalid context 0x600000160180. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update. 

what is wrong? any clues?