Question

我仍然是iOS新手，但我无法弄清楚为什么这不起作用。

我有2个单独的UIImageView的

'背景'。这是一张将应用了图层蒙版的图片，以便您只能看到图像的一部分。
'Mask Image'这是它自己的独立图像，可以旋转，平移，捏缩放。旋转/缩放的代码工作正常，是标准代码。

我要做的是创建一个与“Mask Image”的当前位置/旋转/比例相匹配的CGPath

这是我的代码，用于抓取“蒙版图像”的位置并创建一个CGPAth用作图层蒙版。

如果您转到Xcode并创建一个新的“单一视图应用程序”项目，这里是ViewController的完整复制粘贴

ViewController.h：

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UIGestureRecognizerDelegate>
{
    UIImageView *makskedImageView;
    UIImageView *maskImageView;
}

@end

ViewController.m

#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    UIImage *sourceImage = [UIImage imageNamed:@"forest.jpg"];
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, (sourceImage.size.width/2), (sourceImage.size.height/2))];
    imageView.image = sourceImage;

    [self.view addSubview:imageView];

    makskedImageView = imageView;

    //    Movable Mask
    UIImage *frameBorder = [UIImage imageNamed:@"semiTransSquare.png"];
    maskImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, (frameBorder.size.width/2), (frameBorder.size.height/2))];
    maskImageView.image = frameBorder;

    UIPanGestureRecognizer *panGesture2 = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    [panGesture2 setDelegate:self];
    [maskImageView addGestureRecognizer:panGesture2];
    UIPinchGestureRecognizer *pinchGesture2 = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];
    [pinchGesture2 setDelegate:self];
    [maskImageView addGestureRecognizer:pinchGesture2];
    UIRotationGestureRecognizer *rotateGesture2 = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(handleRotate:)];
    [rotateGesture2 setDelegate:self];
    [maskImageView addGestureRecognizer:rotateGesture2];

    UITapGestureRecognizer *tapGR =[[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(handleTap:)];
    [tapGR setDelegate:self];
    [tapGR setNumberOfTapsRequired:1];
    [maskImageView addGestureRecognizer:tapGR];

    [maskImageView setUserInteractionEnabled:YES];
    // Add to view to make visible;
    [self.view addSubview:maskImageView];

    // apply layer mask to makskedImageView
    [self grabTransform:maskImageView];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)grabTransform:(UIView *)currentView
{
    // build the transform you want
    CGAffineTransform t = CGAffineTransformIdentity;
    CGFloat angle = [(NSNumber *)[currentView valueForKeyPath:@"layer.transform.rotation.z"] floatValue];
    CGFloat scale = [(NSNumber *)[currentView valueForKeyPath:@"layer.transform.scale"] floatValue];
    t = CGAffineTransformConcat(t, CGAffineTransformMakeScale(scale, scale));
    t = CGAffineTransformConcat(t, CGAffineTransformMakeRotation(angle));
    NSLog(@"angle: %f, scale: %f", angle, scale);

    // Create a mask layer
    // Create a mask layer and the frame to determine what will be visible in the view.
    CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
    // CGRect maskRect = currentView.bounds;
    // Frame works a lot better.
    CGRect maskRect = currentView.frame;

    maskRect.origin.x = currentView.frame.origin.x;
    maskRect.origin.y = currentView.frame.origin.y;

    // Make a Path friendly transform.

    CGPoint center = CGPointMake(CGRectGetMidX(currentView.frame), CGRectGetMidY(currentView.frame));
    CGAffineTransform transform = CGAffineTransformIdentity;

    transform = CGAffineTransformTranslate(transform, center.x, center.y);
    transform = CGAffineTransformScale(transform, scale, scale);
    transform = CGAffineTransformRotate(transform, angle);
    transform = CGAffineTransformTranslate(transform, -center.x, -center.y);

    // Create a path and from the rectangle in it.
    CGPathRef path = CGPathCreateWithRect(maskRect, &transform);
    // Set the path to the mask layer.
    [maskLayer setPath:path];
    // Release the path since it's not covered by ARC.
    CGPathRelease(path);
    // Set the mask of the view.
    makskedImageView.layer.mask = maskLayer;


}

#pragma mark - Gestures

-(void)handlePan:(UIPanGestureRecognizer *)recognizer
{
    CGPoint translation = [recognizer translationInView:self.view];
    recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
                                         recognizer.view.center.y + translation.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
    [self grabTransform:[recognizer view]];
}

-(void)handlePinch:(UIPinchGestureRecognizer *)recognizer
{
    recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);

    recognizer.scale = 1;
    [self grabTransform:[recognizer view]];
}

-(void)handleRotate:(UIRotationGestureRecognizer *)recognizer
{
    recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
    recognizer.rotation = 0;
valueForKeyPath:@"layer.transform.rotation"] floatValue];
    [self grabTransform:[recognizer view]];
}

-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

- (void)handleTap:(UIGestureRecognizer *)recognizer
{
    [self grabTransform:[recognizer view]];

}

@end

加2张图片：Forest.jpg＆amp; semiTransSquare.png

现在，当它运行时，它可用于平移，直到我缩放。旋转图像。（由于其他一些代码，现在轮流工作）。

据我所知，尺度与中心一起作为它生长/收缩的点，其中路径似乎从根x，y坐标向外扩展。

这可能是设计的（CGPathCreateWithRect per the docs），但我看不到将变换应用于CGPath的方法，并让它出现在与UIImageView“Mask Image”相同的位置

性能是一个大问题，CIImage的类似解决方案非常滞后，所以想要在CGPath创建层掩码的情况下解决这个问题，如果可能的话，或者同样快的东西。

我错过了什么？仅适用于iOS 6解决方案。

更新：我发现从界限到帧的变化让我获得90％的胜利：

CGRect maskRect = currentView.frame;

路径现在将匹配视图的旋转和位置。剩下的唯一问题是规模是错误的。它匹配原始大小，但如果你缩小，那么它会变得太小，或者如果你长大，它会变得太大。看起来比例不是1：1。现在这么近了。

Answer 1

您是否看过该功能

CGPathCreateCopyByTransformingPath？

它需要CGRect和仿射变换才能实现您的目标。

仅供参考，它是iOS 5 +

Answer 2

您可以使用以下方式获取有效比例因子：

CGFloat zoomScale = sqrtf( powf(currentView.transform.a, 2) + powf(currentView.transform.c, 2) );

不等于：

CGFloat scale = [(NSNumber *)[currentView valueForKeyPath:@"layer.transform.scale"] floatValue];

使用旋转和缩放从UIimageview创建CGpath以用作cglayer掩码

2 个答案: