+(void)drawEllipse:(CGPoint)point withColor:(UIColor*)color withRad:(float)rad{    CGContextRef ctx = UIGraphicsGetCurrentContext();    CGContextSetFillColorWithColor(ctx, [color CGColor]);    CGContextFillEllipseInRect(ctx, CGRectMake(point.x-rad, point.y-rad, 2*rad, 2*rad));}

直接调用传入参数就可以了