For this, we need an image to work with; so, import the Bg image from the first chapter to work with. Make the sprite a global variable as we will need to access it in another function.

So, in the MainScene.h file, we will add an instance of CCSprite as CCSprite* backgroundImage;.

Also, we will add a global float called currentScale to track the current scale value of the background image.

Next, in the init function, we will initialize the variable, as follows:

backgroundImage = [CCSpritespriteWithImageNamed:@"Bg.png"];
backgroundImage.position = CGPointMake(winSize.width/2, winSize.height/2);
[selfaddChild:backgroundImage];

We will add the pinch/zoom recognizer in the init function and set the desired function name that will be responsible for pinching and zooming the image, as follows:

// ** PinchZoom ** //
UIPinchGestureRecognizer* pinchRecognizer = [[UIPinchGestureRecognizeralloc] initWithTarget:self action:@selector(handlePinchGesture:)];

[[UIApplicationsharedApplication].delegate.windowaddGestureRecognizer:pinchRecognizer];

Next, we will add the following function:

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

  NSLog(@"pinch zoom");
  backgroundImage.scale = recognizer.scale;

}

Here, we got the scale value from the recognizer and assigned it to the image.

If you are running it on a device, place two fingers on the screen and bring them close and take them away from each other. If you are using a simulator, you can press the Alt key and drag the mouse on the screen to see the effect.