Question

How can I draw a sector (filled arc) with radial gradient in objective c (Core Graphics)
I use

CGContextDrawRadialGradient

but it draws circle.
It will be good if you say me how to fill any shape by radial gradient. Thanks

Answer 1

Add a path to current context that defines the desired shape and clip the context before drawing. Sample code:

- (void)drawRect:(CGRect)rect
{
    CGPoint c = self.center ;
    // Drawing code
    CGContextRef cx = UIGraphicsGetCurrentContext();

    CGContextSaveGState(cx);
    CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();

    CGFloat comps[] = {1.0,1.0,0.0,1.0,0.0,1.0,0.0,1.0};
    CGFloat locs[] = {0,1};
    CGGradientRef g = CGGradientCreateWithColorComponents(space, comps, locs, 2);


    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, c.x, c.y);
    CGPathAddLineToPoint(path, NULL, c.x, c.y-100);
    CGPathAddArcToPoint(path, NULL, c.x+100, c.y-100, c.x+100, c.y, 100);
    CGPathAddLineToPoint(path, NULL, c.x, c.y);

    CGContextAddPath(cx, path);
    CGContextClip(cx);

    CGContextDrawRadialGradient(cx, g, c, 1.0f, c, 320.0f, 0);

    CGContextRestoreGState(cx);   
    ... // Do some more drawing may be
}