iOS Drawing Circles

问题:

I am trying to create the circles below in my iOS app. I know how to make the circles but am not entirely sure on how to get the points along the arc. It has to be in code not an image. Below is also the code I currently have.

 - (void)drawRect:(CGRect)rect
{
    CGPoint point;
    point.x = self.bounds.origin.x + self.bounds.size.width/2;
    point.y = self.bounds.origin.y + self.bounds.size.height/2;

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetLineWidth(context, 2.0);

    CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);

    CGRect circle = CGRectMake(point.x/2,point.y-point.x/2,point.x,point.x);

    CGContextAddEllipseInRect(context, circle);

    CGContextStrokePath(context);

    for (int i = 0; i<8; i++) {
        CGRect circleMini = CGRectMake(??????,??????,point.x/4,point.x/4);

        CGContextAddEllipseInRect(context, circleMini);
        CGContextStrokePath(context);
    }

}

UPDATED TO ANSWER

 float cita = 0;
for (int i = 0; i<8; i++) {

    CGPoint pointCir = CGPointMake(point.x/2 + radius * cos(cita) , (point.y-point.x/2) + radius * sin(cita) );
    CGRect circleMini = CGRectMake(pointCir.x,pointCir.y,radius/4,radius/4);

    CGContextAddEllipseInRect(context, circleMini);
    CGContextStrokePath(context);
    cita += M_PI / 4.0;
}

回答1:

If (x,y) is the center and r is the radius of your big circle, the center of the i-th external circle will be:

  center(i) = ( x + r * cos(cita) , y + r * sin(cita) )

Start cita in 0 and increment it PI/4 radians for the next circle (or 45 degrees)

Working implementation

CGFloat cita = 0;
CGFloat bigCircleRadius = point.x / 2.0;
CGFloat smallCircleRadius = bigCircleRadius / 4.0;
for (int i = 0; i < 8; i++) {

    CGPoint smallCircleCenter = CGPointMake(point.x  + bigCircleRadius * cos(cita) - smallCircleRadius/2.0 , point.y + bigCircleRadius * sin(cita) - smallCircleRadius / 2.0 );
    CGRect smallCircleRect = CGRectMake(smallCircleCenter.x,smallCircleCenter.y,smallCircleRadius,smallCircleRadius);

    CGContextAddEllipseInRect(context, smallCircleRect);
    CGContextStrokePath(context);
    cita += M_PI / 4.0;
}

Edit: Added implementation and renamed variables.

回答2:

- (void)drawRect:(CGRect)rect
{
    const NSUInteger kNumCircles = 8u;


    CGFloat height = CGRectGetHeight(rect);

    CGFloat smallCircleRadius = height / 10.0f;

    CGRect bigCircleRect = CGRectInset(rect, smallCircleRadius / 2.0f, smallCircleRadius / 2.0f);
    CGFloat bigCircleRadius = CGRectGetHeight(bigCircleRect) / 2.0f;

    CGPoint rectCenter = CGPointMake(CGRectGetMidX(rect), CGRectGetMidY(rect));

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetLineWidth(context, 2.0f);

    CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);

    CGContextAddEllipseInRect(context, bigCircleRect);

    CGContextStrokePath(context);

    CGFloat alpha = 0;


    for (NSUInteger i = 0; i < kNumCircles; i++)
    {
        CGPoint smallCircleCenter = CGPointMake(rectCenter.x  + bigCircleRadius * cos(alpha) - smallCircleRadius/2.0f , rectCenter.y + bigCircleRadius * sin(alpha) - smallCircleRadius / 2.0f );
        CGRect smallCircleRect = CGRectMake(smallCircleCenter.x,smallCircleCenter.y,smallCircleRadius,smallCircleRadius);

        CGContextAddEllipseInRect(context, smallCircleRect);
        CGContextStrokePath(context);
        alpha += M_PI / (kNumCircles / 2.0f);
    }

}