妄撮的撕衣服demo

Cocos2d-x
#1

这几天在研究《Hi Seal》划地的效果，无意间搜到了http://www.cocoachina.com/bbs/read.php?tid=12505&page=1上妄撮的帖子，之后又搜了一些，形成现在的Demo。
1110

现在的功能：
1）擦除图片
2）提供了一个计算擦除百分比的方法

未实现的功能：
1）Shake复原 （似乎cocos2dx不支持）
2）原版妄撮里，纸张撕裂的边缘效果
3）似乎还有很多……

废话不多说，直接上关键代码：
头文件：（头文件里写USING_NS_CC不知道是不是个坏习惯，求教）

#include "cocos2d.h"
USING_NS_CC;

class ScratchSprite : public CCLayer
{
public:
    static ScratchSprite *create(const char *scratchSprite, const char *blendSprite);
    bool initWithScratchAndBlendSprites(const char *scratchSprite, const char *blendSprite);
    
    virtual void registerWithTouchDispatcher(void);
    
    virtual bool ccTouchBegan(CCTouch *pTouch, CCEvent *pEvent);
    virtual void ccTouchMoved(CCTouch *pTouch, CCEvent *pEvent);
    virtual void ccTouchEnded(CCTouch *pTouch, CCEvent *pEvent);
    virtual void ccTouchCancelled(CCTouch *pTouch, CCEvent *pEvent);
    
private:
    void resetRenderTexture();
    void tick(float dt);
    
    float alphaPercent();
    
private:
    CCSprite *_scratchSprite;
    CCRenderTexture *_renderTexture;
    CCSprite *_blendSprite;
};

实现：

#define BLEND_INIT_POSITION ccp(10000, 10000)

ScratchSprite *ScratchSprite::create(const char *scratchSprite, const char *blendSprite)
{
    ScratchSprite *scratch = new ScratchSprite();
    if ( scratch && scratch->initWithScratchAndBlendSprites(scratchSprite, blendSprite) ) {
        scratch->autorelease();
        
        return scratch;
    } else {
        delete scratch;
        scratch = NULL;
        
        return NULL;
    }
}

bool ScratchSprite::initWithScratchAndBlendSprites(const char *scratchSprite, const char *blendSprite)
{
    CCSize spriteSize = CCSizeZero;
    _scratchSprite = CCSprite::create(scratchSprite);
    spriteSize = _scratchSprite->getContentSize();
    setContentSize(spriteSize);
    
    _scratchSprite->setPosition(ccp(spriteSize.width/2, spriteSize.height/2));
    _scratchSprite->retain();
    
    _blendSprite = CCSprite::create(blendSprite);
    _blendSprite->setPosition(BLEND_INIT_POSITION);
    _blendSprite->setBlendFunc((ccBlendFunc){GL_ZERO, GL_ONE_MINUS_SRC_ALPHA});
    _blendSprite->retain();
    
    _renderTexture = CCRenderTexture::create(spriteSize.width, spriteSize.height);
    _renderTexture->setPosition(_scratchSprite->getPosition());
    _renderTexture->getSprite()->setBlendFunc((ccBlendFunc){GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA});
    addChild(_renderTexture);
    
    resetRenderTexture();
    
    schedule(schedule_selector(ScratchSprite::tick));
    setTouchEnabled(true);
    
    return true;
}

void ScratchSprite::resetRenderTexture()
{
    _renderTexture->begin();
    _scratchSprite->visit();
    _renderTexture->end();
}

void ScratchSprite::tick(float dt)
{
    _renderTexture->begin();
    
    glColorMask(false, false, false, true);
    _blendSprite->visit();
    glColorMask(true, true, true, true);
    
    _renderTexture->end();
}

float ScratchSprite::alphaPercent()
{
    int width = getContentSize().width;
    int height = getContentSize().height;
    
    int numberOfTransparent = 0;
    int numberOfPixels = width * height;
    
    int bytesPerRow = width * 4;
    
    GLubyte *buffer = new GLubyte;
    if ( ! buffer ) {
        CCLOG("cocos2dx: no enough space!");
        delete ] buffer;
        return 0.0f;
    }
    
    _renderTexture->begin();
    glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
    _renderTexture->end();
    
    int x, y;
    for ( x = 0; x < width; ++x ) {
        for ( y = 0; y < height; ++y ) {
            GLubyte alpha = buffer;
            if ( alpha == 0 ) {
                numberOfTransparent++;
            }
        }
    }
    
    delete ] buffer;
    
    return 100.0f * numberOfTransparent / numberOfPixels;
}

void ScratchSprite::registerWithTouchDispatcher()
{
    CCDirector::sharedDirector()->getTouchDispatcher()->addTargetedDelegate(this, 0, true);
}

bool ScratchSprite::ccTouchBegan(CCTouch *pTouch, CCEvent *pEvent)
{
    CCPoint location = this->convertTouchToNodeSpace(pTouch);
    if ( ! this->boundingBox().containsPoint(location) ) {
        return false;
    }
    
    _blendSprite->setPosition(location);
    
    return true;
}

void ScratchSprite::ccTouchMoved(CCTouch *pTouch, CCEvent *pEvent)
{
    CCPoint location = this->convertTouchToNodeSpace(pTouch);
    if ( this->boundingBox().containsPoint(location) ) {
        _blendSprite->setPosition(location);
    }
}

void ScratchSprite::ccTouchEnded(CCTouch *pTouch, CCEvent *pEvent)
{
    _blendSprite->setPosition(BLEND_INIT_POSITION);
    CCLOG("Transparent Percentage: %.0f", alphaPercent());
}

void ScratchSprite::ccTouchCancelled(CCTouch *pTouch, CCEvent *pEvent)
{
    _blendSprite->setPosition(BLEND_INIT_POSITION);
    CCLOG("Transparent Percentage: %.0f", alphaPercent());
}

高手请指点一下各种不错（逻辑、代码规范、结构什么的）

#2

传一下删掉libs文件夹之后的项目文件。当前cocos2dx版本是cocos2d-2.1rc0-x-2.1.3

#3

发现cocos2d-iphone在做iOS游戏时比cocos2d-x好用很多，我讨厌跨平台:@