drawing CLLocations in a CGContext

gistfile1.txt

	NSUInteger pointCount = self.waypoints.count;
	MKMapPoint* points = calloc(sizeof(MKMapPoint), pointCount);
	CGFloat minX = CGFLOAT_MAX, minY = CGFLOAT_MAX;
	CGFloat maxX = 0, maxY = 0;
	
	{
		NSInteger i = 0;
		for (CLLocation* location in self.waypoints)
		{
			MKMapPoint point = MKMapPointForCoordinate(location.coordinate);
			points[i] = point;
			i++;
			
			minX = MIN(point.x, minX);
			minY = MIN(point.y, minY);
			
			maxX = MAX(point.x, maxX);
			maxY = MAX(point.y, maxY);
		}
	}
	
	CGFloat deltaX = maxX - minX;
	CGFloat deltaY = maxY - minY;
	
	CGFloat r = MAX(deltaX,deltaY);
	
	UIImage* image = nil;
	CGFloat inset = round(size.width / 10);
	CGFloat imageExtent = size.width * [UIScreen mainScreen].scale;
	CGFloat nettoExtent = imageExtent - inset - inset;
	
	// xShift & yShift ensure that the scaled image is rendered centered
	CGFloat xShift = (nettoExtent - (deltaX / r * nettoExtent)) * 0.5;
	CGFloat yShift = (nettoExtent - (deltaY / r * nettoExtent)) * 0.5;
	
	UIGraphicsBeginImageContext(CGSizeMake(imageExtent, imageExtent));
	{
		if (pointCount > 3)
		{
			CGContextRef context = UIGraphicsGetCurrentContext();
			
			NSInteger i = 0;
			for (i = 0; i <= pointCount; i++)
			{
				MKMapPoint mkPoint = points[i % pointCount]; // going till <= pointCount to have the first point count twice, closing the path
				
				// add the inset and the shift to have a little padding and a centered drawing
				CGPoint cgPoint = CGPointMake(inset + xShift + ((mkPoint.x - minX) / r * nettoExtent),
											  inset + yShift + ((mkPoint.y - minY) / r * nettoExtent));
				if (i == 0)
				{
					CGContextMoveToPoint(context, cgPoint.x, cgPoint.y);
				}
				else
				{
					CGContextAddLineToPoint(context, cgPoint.x, cgPoint.y);
				}
			}
			CGContextSetLineWidth(context, 2);
			[[UIColor blackColor] setStroke];
			CGContextStrokePath(context);
		}
		image = UIGraphicsGetImageFromCurrentImageContext();
	}
	UIGraphicsEndImageContext();
	free(points);
	return image;