Gradient color to bubble

Question

I am drawing bubble using core graphics in my application.Now i want to set gradient color effect to my bubble.i can give radial effect to that bubble. but i want to set something different king of gradient effect.Here is my code using radial gradient :

    CGGradientRef gradient;
    CGColorSpaceRef colorSpace;
    CGFloat locations[] = {0.0,1.0};
    CGFloat components[] = { red2,green2,blue2,1.0,red1,green1,blue1,1.0  };
    colorSpace = CGColorSpaceCreateDeviceRGB();
    gradient = CGGradientCreateWithColorComponents(colorSpace,components,locations,
                                                   sizeof(locations)/sizeof(CGFloat));
    CGPoint start = CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2 ), end = CGPointMake(self.bounds.size.width/2 , self.bounds.size.height/2);
    CGFloat startRadius = 0.0, endRadius = radius - borderWidth;
    CGContextDrawRadialGradient(contextRef,gradient,start,startRadius,end,endRadius,0);
    CGGradientRelease(gradient);
    CGColorSpaceRelease(colorSpace);

I have attached image here ,like that i want gradient colour.Please help me.Thanking you.