单侧边角的反向UIBezierPath

Question

我想创建一个掩码路径，其最终输出将是带有凹面的角。

我已经使用UIBezierPath方法创建了一个-bezierPathWithRoundedRect:byRoundingCorners:cornerRadii:，并指定只需要倒圆一个角（在此示例中，UIRectCornerBottomLeft），我认为通过反转此路径，我应该首先得到应该削减的东西。为此，我正在尝试-bezierPathByReversingPath，但似乎没有什么区别（有或没有，因为我正在获得正常的贝塞尔曲线路径，而不是相反的路径）]

这是我到目前为止尝试过的：

UIView *vwTest = [[UIView alloc] init];
[vwTest setFrame:CGRectMake(100.0f, 100.0f, 100.0f, 100.0f)];
[vwTest setBackgroundColor:[UIColor redColor]];
[self.view addSubview:vwTest];

UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:vwTest.bounds
                                               byRoundingCorners:UIRectCornerBottomLeft
                                                     cornerRadii:CGSizeMake(50.0f, 50.0f)];

//get reverse path but doesn't seem to work as I think it should
maskPath = [maskPath bezierPathByReversingPath]; 

CAShapeLayer *maskLayer = [CAShapeLayer layer];
[maskLayer setFrame:vwTest.bounds];
[maskLayer setPath:maskPath.CGPath];

[vwTest.layer setMask:maskLayer];
[vwTest.layer setMasksToBounds:YES];
[vwTest setNeedsDisplay];

---

根据下面的图片，我想要实现的是显示UIView的红色部分，并消除其余区域。

---

目前，我正在像子视图上一样在子视图上做文章，并将一个子视图的颜色与主视图的背景色同步（糟透了，但至少我得到了所需的输出：]：

[self.view setBackgroundColor:[UIColor lightGrayColor]];

UIView *vwTest = [[UIView alloc] init];
[vwTest setFrame:CGRectMake(100.0f, 100.0f, 100.0f, 100.0f)];
[vwTest setBackgroundColor:[UIColor redColor]];
[self.view addSubview:vwTest];

UIView *vwPatch = [[UIView alloc] init];
[vwPatch setFrame:vwTest.bounds];
[vwPatch setBackgroundColor:vwTest.superview.backgroundColor];
[vwTest addSubview:vwPatch];

UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:vwPatch.bounds
                                               byRoundingCorners:UIRectCornerBottomLeft
                                                     cornerRadii:CGSizeMake(50.0f, 50.0f)];
CAShapeLayer *maskLayer = [CAShapeLayer layer];
[maskLayer setFrame:vwPatch.bounds];
[maskLayer setPath:maskPath.CGPath];

[vwPatch.layer setMask:maskLayer];
[vwPatch.layer setMasksToBounds:YES];
[vwPatch setNeedsDisplay];

---

有人，请指出正确的方向。

Answer 1

[通过查看问题中的代码，我假设您希望左下角（因为使用UIRectCornerBottomLeft）是半径为30的凹面。您不能使用bezierPathByReversingPath，因为它就是全部从字面上反转路径，它也在文档中说：

反转路径不一定会在渲染时改变路径的外观。

编辑：现在已将图像添加到问题中，OP希望形状的倒数：

bezierPathByReversingPath

路径的形状在问题中的OPs图像中为红色。

---

发布图像之前的答案-可能用于其他人

以下代码将产生这种形状：

CAShapeLayer *mask = [CAShapeLayer layer];
mask.frame = view.layer.bounds;

UIBezierPath *path = [UIBezierPath bezierPath];
CGFloat radius = 50;
CGRect rect = mask.bounds;
[path moveToPoint:CGPointMake(CGRectGetMinX(rect), CGRectGetMaxY(rect))];
[path addLineToPoint:CGPointMake(CGRectGetMinX(rect), CGRectGetMaxY(rect) - radius)];
[path addArcWithCenter:CGPointMake(CGRectGetMinX(rect) + radius, CGRectGetMaxY(rect) - radius) radius:radius startAngle:M_PI endAngle:M_PI_2 clockwise:NO];
[path closePath];

mask.path = path.CGPath;
view.layer.mask = mask;

更新：有用的类别

CGFloat cornerRadius = 30;

CGRect rect = CGRectMake(0, 0, 200, 100);

UIBezierPath *path = [UIBezierPath bezierPath];

// Draw the complete sides
[path moveToPoint:rect.origin];
[path addLineToPoint:CGPointMake(CGRectGetMaxX(rect), CGRectGetMinY(rect))];
[path addLineToPoint:CGPointMake(CGRectGetMaxX(rect), CGRectGetMaxY(rect))];

// Stop short for the start of the arc
[path addLineToPoint:CGPointMake(CGRectGetMinX(rect) + cornerRadius, CGRectGetMaxY(rect))];

// Concave arc
[path addArcWithCenter:CGPointMake(CGRectGetMinX(rect), CGRectGetMaxY(rect)) radius:cornerRadius startAngle:0 endAngle:M_PI_2 * 3 clockwise:NO];

// Complete the path
[path closePath];

上的类别，因此您可以选择哪个角（UIBezierPath s的位掩码）和半径。

UIBezierPath + RDHConcaveCorners.h

UIRectCorner

UIBezierPath + RDHConcaveCorners.m

@interface UIBezierPath (RDHConcaveCorners)

+(instancetype)bezierPathWithRoundedRect:(CGRect)rect byConcaveRoundingCorners:(UIRectCorner)corners cornerRadius:(CGFloat)radius;

@end

Answer 2

感谢Rich，支持快捷代码

@implementation UIBezierPath (RDHConcaveCorners)

+(instancetype)bezierPathWithRoundedRect:(CGRect)rect byConcaveRoundingCorners:(UIRectCorner)corners cornerRadius:(CGFloat)cornerRadius
{
    CGFloat halfWidth = CGRectGetWidth(rect) / 2;
    CGFloat halfHeight = CGRectGetHeight(rect) / 2;
    if (cornerRadius > halfWidth || cornerRadius > halfHeight) {
        cornerRadius = MIN(halfWidth, halfHeight);
    }

    UIBezierPath *path = [self bezierPath];

    CGPoint topLeft = CGPointMake(CGRectGetMinX(rect), CGRectGetMinY(rect));
    if (corners & UIRectCornerTopLeft) {
        [path moveToPoint:CGPointMake(topLeft.x, topLeft.y + cornerRadius)];
        [path addArcWithCenter:topLeft radius:cornerRadius startAngle:M_PI_2 endAngle:0 clockwise:NO];
    } else {
        [path moveToPoint:topLeft];
    }

    CGPoint topRight = CGPointMake(CGRectGetMaxX(rect), CGRectGetMinY(rect));
    if (corners & UIRectCornerTopRight) {
        [path addLineToPoint:CGPointMake(topRight.x - cornerRadius, topRight.y)];
        [path addArcWithCenter:topRight radius:cornerRadius startAngle:M_PI endAngle:M_PI_2 clockwise:NO];
    } else {
        [path addLineToPoint:topRight];
    }

    CGPoint bottomRight = CGPointMake(CGRectGetMaxX(rect), CGRectGetMaxY(rect));
    if (corners & UIRectCornerBottomRight) {
        [path addLineToPoint:CGPointMake(bottomRight.x, bottomRight.y - cornerRadius)];
        [path addArcWithCenter:bottomRight radius:cornerRadius startAngle:M_PI_2 * 3 endAngle:M_PI clockwise:NO];

    } else {
        [path addLineToPoint:bottomRight];
    }

    CGPoint bottomLeft = CGPointMake(CGRectGetMinX(rect), CGRectGetMaxY(rect));
    if (corners & UIRectCornerBottomLeft) {
        [path addLineToPoint:CGPointMake(bottomLeft.x + cornerRadius, bottomLeft.y)];
        [path addArcWithCenter:bottomLeft radius:cornerRadius startAngle:0 endAngle:M_PI_2 * 3 clockwise:NO];
    } else {
        [path addLineToPoint:bottomLeft];
    }

    // Complete the path
    [path closePath];

    return path;
}

@end