如何在cocos2d精灵图像上实现放大/缩小效果？

Question

我正在开发模块，在其中，我从照片库中选择图像，并将其放入精灵中。我想对精灵图像实现放大/缩小效果，就像相机相册图像放大/缩小效果一样。有人能指点我如何实施吗？

我发现，我必须在ccTouchBegan中检测两个触摸事件，然后根据两个手指触摸事件值的距离来调整精灵的缩放大小。

谁能告诉我：

• 如何在ccTouchBegan中检测两个手指触摸值
• 如何允许用户触摸和放大精灵图像？请给我样品。我已经尝试了一些来自这个URL的东西，但是不适合我的需求。

谢谢。

Answer 1

使用手势识别器进行缩放会更简单：

    // on initializing your scene:
    UIPinchGestureRecognizer* PinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget: self action: @selector (zoom:)];
    [[[Director sharedDirector] openGLView] addGestureRecognizer: PinchGesture];
...
/// zoom callback:
-(void) zoom: (UIPinchGestureRecognizer*) gestureRecognizer
{
    if (([gestureRecognizer state] == UIGestureRecognizerStateBegan) || ([gestureRecognizer state] == UIGestureRecognizerStateChanged))
        yourSprite.scale = [gestureRecognizer scale];
}

Answer 2

1)第一步，您需要创建两个变量。

BOOL canPinch; 
float oldScale;

2)使用brigadir的:)答案并将其添加到init方法中

UIPinchGestureRecognizer* pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action: @selector (zoom:)];
[[[CCDirector sharedDirector] openGLView] addGestureRecognizer:pinchGesture];

3)

- (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{     
    NSArray* allTouches = [[event allTouches] allObjects];
    UITouch* touch = [touches anyObject]; 
    CGPoint location = [self convertTouchToNodeSpace:touch];;

    CGRect particularSpriteRect = CGRectMake(spriteToZoom.position.x-[spriteToZoom boundingBox].size.width/2, spriteToZoom.position.y-[spriteToZoom boundingBox].size.height/2, [spriteToZoom boundingBox].size.width, [spriteToZoom boundingBox].size.height);

    if(CGRectContainsPoint(particularSpriteRect, location)) 
    {  
        if ([allTouches count] == 2) 
        {     
            canPinch = YES; 
            return;
        }   
        else if ([allTouches count] == 1)
        {  
            CGPoint touchLocation = [self convertTouchToNodeSpace:touch];

            CGPoint oldTouchLocation = [touch previousLocationInView:touch.view];
            oldTouchLocation = [[CCDirector sharedDirector] convertToGL:oldTouchLocation];
            oldTouchLocation = [self convertToNodeSpace:oldTouchLocation];

            CGPoint translation = ccpSub(touchLocation, oldTouchLocation);    
            [self panForTranslation:translation]; 
        }

    }
    canPinch = NO;
}

- (void)panForTranslation:(CGPoint)translation 
{     
    CGPoint newPos = ccpAdd(spriteToZoom.position, translation);
    spriteToZoom.position = newPos; 
}

- (void)zoom: (UIPinchGestureRecognizer*) gestureRecognizer
{
    if (canPinch) 
    {
        if (([gestureRecognizer state] == UIGestureRecognizerStateBegan) || ([gestureRecognizer state] == UIGestureRecognizerStateChanged))
        {       
            spriteToZoom.scale = oldScale + [gestureRecognizer scale]-(oldScale != 0 ? 1 : 0);  
        }
        if ([gestureRecognizer state] == UIGestureRecognizerStateEnded)
        { 
            oldScale = spriteToZoom.scale; 
        } 
    } 
}