How to draw a gradient circle

Please, how should I achieve it?

I want to draw a gradient circle, the color is white, and the alpha starts to change according to the specified(0%, 10%, 30%) position.

I tried CGContextDrawRadialGradient, but the effect is wrong. Below is my code and Demo.

code:

CGFloat colors[] = {
    1, 1, 1, 0.35,
    1, 1, 1, 0.10,
    1, 1, 1, 0.0,
  };

CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, 3);
   

CGContextRef graCtx = UIGraphicsGetCurrentContext();
   
CGContextDrawRadialGradient(graCtx, gradient, self.center, 75, self.center, 100, kCGGradientDrawsBeforeStartLocation | kCGGradientDrawsAfterEndLocation);

CGColorSpaceRelease(rgb);

sample: