Rendering a radial gradient on the iphone

radial.m

- (UIImage *)radialGradientImage:(CGSize)size start:(float)start end:(float)end centre:(CGPoint)centre radius:(float)radius {
	// Render a radial background
	// http://developer.apple.com/library/ios/#documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_shadings/dq_shadings.html

	// Initialise
	UIGraphicsBeginImageContextWithOptions(size, YES, 1);

	// Create the gradient's colours
	size_t num_locations = 2;
	CGFloat locations[2] = { 0.0, 1.0 };
	CGFloat components[8] = { start,start,start, 1.0,  // Start color
		end,end,end, 1.0 }; // End color
	
	CGColorSpaceRef myColorspace = CGColorSpaceCreateDeviceRGB();
	CGGradientRef myGradient = CGGradientCreateWithColorComponents (myColorspace, components, locations, num_locations);
	
	// Normalise the 0-1 ranged inputs to the width of the image
	CGPoint myCentrePoint = CGPointMake(centre.x * size.width, centre.y * size.height);
	float myRadius = MIN(size.width, size.height) * radius;
	
	// Draw it!
	CGContextDrawRadialGradient (UIGraphicsGetCurrentContext(), myGradient, myCentrePoint,
								 0, myCentrePoint, myRadius,
								 kCGGradientDrawsAfterEndLocation);
	
	// Grab it as an autoreleased image
	UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
	
	// Clean up
	CGColorSpaceRelease(myColorspace); // Necessary?
	CGGradientRelease(myGradient); // Necessary?
	UIGraphicsEndImageContext(); // Clean up
	return image;
}

I've created version with alpha&UIColor:
https://gist.github.com/Maciekp/6678988