BackgroundLayer is not positioned in the center of the screen.

gistfile1.m

// BackgroundLayer
-(id) init {
    self = [super init];
    if(self != nil) {
        CCSprite *backgroundImage;
        if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
            backgroundImage = [CCSprite spriteWithFile:@"background.png"];
        } else {
            backgroundImage = [CCSprite spriteWithFile:@"backgroundiPhone.png"];
        }
        
        CGSize screenSize = [[CCDirector sharedDirector] winSize];
        [backgroundImage setPosition:CGPointMake(screenSize.width/2, screenSize.height/2)];
        
        [self addChild:backgroundImage z:0 tag:0];
    }
    return self;
}


// GameScene
-(id) init {
    self = [super init];
    if(self != nil) {
        BackgroundLayer *backgroundLayer = [BackgroundLayer node];
        [self addChild:backgroundLayer z:0];
    }
    return self;
}


// app delegate
[director_ pushScene:[GameScene node]];