Question

我在底部创建了一个UIImageView的双层图层，并使用此方法创建了一个叠加层：

UIImage *bottomImage = self.imageView.image;
UIImage *image       = self.urlFoto.image;

CGSize newSize = CGSizeMake(640, 640);
UIGraphicsBeginImageContext( newSize );

[bottomImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];

[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeNormal alpha:1.0];

UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

在此之后，我添加了一个用捏合手势调整图像大小的方法：

- (IBAction)scaleImage:(UIPinchGestureRecognizer *)recognizer {

    recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
    recognizer.scale = 1;
}

但是当我在照片库中保存照片时，我无法获得叠加的当前尺寸，并且我在叠加（图像）上看到相同尺寸640,640，我想错过的代码在这里：

[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeNormal alpha:1.0];

在CGRectMake(0,0,newSize.width,newSize.height)知道正确的方法，以便在压缩后获得UIImageView的当前大小？

Answer 1

绘图时，必须记住比例变换。因此，您必须根据手势调整的UIImageView的最终比例绘制叠加图像。

你可以得到这样的最终视角：

CGFloat scale = view.transform.a;

字母a在这里很重要。它是宽度变换的值。因此，假设您按比例缩放图像（宽度和高度相同的比例），则可以使用它来获得通用比例

关于比例的更多细节：

CGAffineTransform的结构定义为

struct CGAffineTransform {
  CGFloat a, b, c, d;
  CGFloat tx, ty;
};

和

CGAffineTransformMakeScale(CGFloat sx, CGFloat sy)

按照文档

进行操作

返回一个按`（sx，sy）'缩放的变换：

t'= [sx 0 0 sy 0 0]

为了更好地理解，请参阅此示例代码：

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 100, 100)];
view.backgroundColor = [UIColor redColor];
[self.view addSubview:view];

view.transform = CGAffineTransformScale(view.transform, 0.5, 0.5);
NSLog(@"Transform 1: %f", view.transform.a);

view.transform = CGAffineTransformScale(view.transform, 0.5, 0.5);
NSLog(@"Transform 2: %f", view.transform.a);

打印到控制台后面：

Transform 1: 0.500000
Transform 2: 0.250000

第一次变换将0.5比例缩放为默认比例1.0
第二变换使0.5比例缩放到已经缩放的0.5 - >将当前0.5与新的0.5比例相乘
等

Answer 2

Step 1：在.h文件中声明

CGFloat lastScale;

Step 2：在.m文件中替换您的手势方法

- (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer {

    if([gestureRecognizer state] == UIGestureRecognizerStateBegan) {
        // Reset the last scale, necessary if there are multiple objects with different scales
        lastScale = [gestureRecognizer scale];
    }

    if ([gestureRecognizer state] == UIGestureRecognizerStateBegan ||
        [gestureRecognizer state] == UIGestureRecognizerStateChanged) {

        CGFloat currentScale = [[[gestureRecognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];

        // Calculate the New Scale of UIImageView
        CGFloat newScale = 1 -  (lastScale - [gestureRecognizer scale]);

        // Store Your Imageview's transform
        CGAffineTransform transorm = simageView.transform;
        // Convert your Imageview to Identity (original Size)
        [imageView setTransform:CGAffineTransformIdentity];
        // Save Rect Of UIImageView
        CGRect actualRect = self.view.frame;
        // Apply Transform to Imageview to make it scaled
        [imageView setTransform:transorm];

        // Now calculate new frame size of your ImageView
        NSLog(@"width %f height %f",(imageView.frame.size.width*newScale), (imageView.frame.size.height*newScale));
    }
}

获取UIImageView的当前大小

2 个答案: