Avoid dragging sprite touching in transparent part in cocos2d

Question

I'm making an app that you can drag objects around the screen, but the object are not perfect squares so i'm trying to avoid transparent pixels. Im using KKPixelMaskSprite class to do it, but it's not working properly Can anyone point me in the right direction? I have a class that inherits from that class like following:

 @interface MyClass : KKPixelMaskSprite

And then i'm reading the touches with this:

for (CCSprite *sprite in [_myLayer children]) {
        if ([sprite isKindOfClass:[MyClass class]]) {
            MyClass * object = (MyClass *)sprite;
            if (CGRectContainsPoint(object.boundingBox, touchLocation) && ![object pixelMaskContainsPoint:touchLocation]) {
                _selectedObject = object;
            }
        }
    }

And them moving _selectedObject around the screen,

The problem is that the selection is not perfect (it's not close to that), Does anyone have a solution ab that? is there any other path i can follow?

Thank you in advance

Answer 1

In this case you have to use pixel perfect collision. Test the point that you touched is pixel of the sprite..

http://www.learn-cocos2d.com/2011/12/fast-pixelperfect-collision-detection-cocos2d-code-1of2/