'Circle' type not in center

[xilibro]

as you can see, not totally in center, how can i fix this issure

[xilibro]

[xilibro]

I do not know how to add a new pull request, so i put the solved code here.
in animations/RTSpinKitCircleAnimation.m, i changed the following code:
`

CGFloat radius = size.width / 2; 
CGFloat circleSize = size.width / 4;
CGFloat circleRadius = circleSize / 2; // added by xilibro 2017-11-09 15:39:59

for (NSInteger i=0; i < 8; i+=1) {
    CALayer *circle = [CALayer layer];

    CGFloat angle = i * M_PI_4; // M_PI_4 = 45°
    CGFloat x = radius + sinf(angle) * radius - circleRadius; // altered by xilibro 2017-11-09 
    CGFloat y = radius - cosf(angle) * radius - circleRadius; // altered by xilibro
   ... ...

`
minus circleself's radius solved the issure.
RTSpinKitFadingCircleAnimation.m use the same way to solve issure

[wumke]

I also noticed that, only in iOS, the circle is shifted slightly to the right.
I used fadingCircleAlt and substracted CGFloat circleRadius = size.width / 16; from x and y of the frame.