ios - 使用 Objective-C 合并两个 UIImageView，其中一个在使用转换后进行修改

Question

我正在尝试创建一个 View Controller 来混合两个 UIImage。其中一个是静态的，作为背景的肌动蛋白，另一个可以缩放、拖动和旋转以将其放置在第一个内部我想要的位置。

我创建了一个这样的测试 View Controller :



蓝色背景( _backImageView )和马里奥图像( _marioImageView )都是同一级别的 UIImageViews(没有一个是另一个的子级)。我像这样处理所有手势识别器:

@interface ViewController () <UIGestureRecognizerDelegate>

@property (strong, nonatomic) IBOutlet UIPanGestureRecognizer *pan;
@property (strong, nonatomic) IBOutlet UIPinchGestureRecognizer *pinch;
@property (strong, nonatomic) IBOutlet UIRotationGestureRecognizer *rotation;

@end

@implementation ViewController

- (void)viewDidLoad
{
  [super viewDidLoad];

  _pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(move:)];
  [_marioImageView addGestureRecognizer:_pan];

  _pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(resize:)];
  [_marioImageView addGestureRecognizer:_pinch];

  _rotation = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotate:)];
  [_marioImageView addGestureRecognizer:_rotation];
}



- (void)move:(UIPanGestureRecognizer *)pan
{
  CGPoint translation = [pan translationInView:_backImageView];

  CGPoint newCenter = CGPointMake(pan.view.center.x + translation.x,
                              pan.view.center.y + translation.y);

  CGPoint newBottomRight = CGPointMake(newCenter.x + pan.view.frame.size.width / 2,
                                     newCenter.y + pan.view.frame.size.height / 2);

  CGPoint newOrigin = CGPointMake(newCenter.x - pan.view.frame.size.width / 2,
                                newCenter.y - pan.view.frame.size.height / 2);

  if (CGRectContainsPoint(_backImageView.frame, newBottomRight) &&
    CGRectContainsPoint(_backImageView.frame, newOrigin)) {

    pan.view.center = newCenter;
    [pan setTranslation:CGPointZero inView:_backImageView];
  }
}

- (void)resize:(UIPinchGestureRecognizer *)pinch
{
  if (CGRectContainsRect(_backImageView.frame, pinch.view.frame)) {
    pinch.view.transform = CGAffineTransformScale(pinch.view.transform, pinch.scale, pinch.scale);
    pinch.scale = 1.0;
  }
}

- (void)rotate:(UIRotationGestureRecognizer *)rotation
{
  if (CGRectContainsRect(_backImageView.frame, rotation.view.frame)) {
    rotation.view.transform = CGAffineTransformRotate(rotation.view.transform, rotation.rotation);
    rotation.rotation = 0;
  }
}

然后，当我触摸“混合图像”按钮时，它就是这样做的(
_finalImageView 是另一个 UIImageView，用于查看混合的结果图像。

- (IBAction)mixImages:(id)sender
{
  UIImage *backImage = _backImageView.image;
  UIImage *marioImage = _marioImageView.image;

  CGSize finalSize = backImage.size;
  CGSize marioSize = marioImage.size;

  UIGraphicsBeginImageContext(finalSize);

  [backImage drawInRect:CGRectMake(0, 0, finalSize.width, finalSize.height)];

  CGPoint relativeOrigin = [_marioImageView convertPoint:_marioImageView.frame.origin toView:_backImageView];

  [marioImage drawInRect:CGRectMake(relativeOrigin.x,
                                  relativeOrigin.y,
                                  marioSize.width,
                                  marioSize.height)];

  UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();

  UIGraphicsEndImageContext();

  [_finalImageView setImage:finalImage];
}   

问题是，在最终图像中， 马里奥图像显示没有任何变换 (没有比例，没有旋转，任何东西)。

我做错了什么？

谢谢

Answer 1

当你这样做 imageView.image ，它只返回 image没有任何转变。您需要保存所有这些转换，并且您需要编写自己的代码，以从 ImageView 中提取转换后的图像。

一种方法是在旋转/缩放/变换后截取 imageview:

    //call this method after the rotation/scaling is done i.e in your mix method
    -(UIImage *)screenshotImageView :(UIImageView *)imgV{

    UIGraphicsBeginImageContext(imgV.frame.size);

    CGContextRef c = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(c, imgV.frame.origin.x, imgV.frame.origin.y);

    [self.view.layer renderInContext:c];
       image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;

    }

因此，在这种情况下，您要合并的两个图像方法将是:

    UIImage *backImage = [self screenshotImageView:_backImageView];
    UIImage *marioImage =[self screenshotImageView:_marioImageView];

使用返回的图像根据需要合并图像。

另一种方法是根据图像属性获取转换后的图像:

假设您在 imageView 中翻转了图像，如果您想获取翻转后的图像:

你可以试试:

     UIImage* flippedImage = [UIImage imageWithCGImage:imgView.image.CGImage
                                                scale:imgView.image.scale
                                          orientation:UIImageOrientationUpMirrored];