Mask View

maskview.swift

    UIView *overlay = [[UIView alloc] initWithFrame:window.bounds];
    overlay.backgroundColor = [UIColor colorWithHex:0x3ED4B6];
    
    UIBezierPath *path = [UIBezierPath bezierPathWithRect:overlay.bounds];
    
    // transparent circle rect
    CGRect rect = CGRectMake(CGRectGetMidX(overlay.bounds) - 41, CGRectGetMidY(overlay.bounds) - 41, 82, 82);
    [path appendPath:[UIBezierPath bezierPathWithOvalInRect:rect]];

    CAShapeLayer *shapeLayer = [CAShapeLayer layer];
    shapeLayer.frame = overlay.bounds;
    shapeLayer.fillColor = [UIColor blackColor].CGColor;
    shapeLayer.fillRule = kCAFillRuleEvenOdd;
    shapeLayer.path = path.CGPath;

    overlay.layer.mask = shapeLayer;
    [window addSubview:overlay];