前些时候想用不规则按钮，按钮的图片是一张矩形的png图片，很可能图片的实际有效的显示内容只占整个png图片的很小一部分，剩下的大部分都是png图片的透明区域，我们想把这部分透明区域过滤掉，实现一个触摸到有真实像素时按钮才响应的效果。

上网找了些资料，有继承Button的，也有使用图片的，判定的时候根据触摸点的位置是否有像素来筛选。在这里分享一下判断是否点击到像素的方法。

HelloWorldScene.h

class HelloWorld : public cocos2d::Layer

{

public:

HelloWorld();

~HelloWorld();

    static cocos2d::Scene* createScene();

    virtual bool init();

    CREATE_FUNC(HelloWorld);

virtual bool onTouchBegan(Touch *pTouch, Event *pEvent);

virtual void onTouchMoved(Touch *touch, Event *unused_event);

virtual void onTouchEnded(Touch *touch, Event *unused_event);

EventListenerTouchOneByOne* touchListener;

private:

RenderTexture* _renderTexture;

Sprite* _spr;

};

HelloWorldScene.cpp

bool HelloWorld::init()

{

    if ( !Layer::init() )

    {

        return false;

    }

auto winsize = Director::getInstance()->getWinSize();

touchListener = EventListenerTouchOneByOne::create();

touchListener->setSwallowTouches(true);

touchListener->onTouchBegan = CC_CALLBACK_2(HelloWorld::onTouchBegan, this);

touchListener->onTouchMoved = CC_CALLBACK_2(HelloWorld::onTouchMoved, this);

touchListener->onTouchEnded = CC_CALLBACK_2(HelloWorld::onTouchEnded, this);

this->_eventDispatcher->addEventListenerWithSceneGraphPriority(touchListener, this);

auto _sNameN = "hat.png";

this->_spr = Sprite::create(_sNameN);

this->_spr->setPosition(Vec2(400, 200));

this->addChild(this->_spr, 1);

this->_renderTexture = RenderTexture::create(this->_spr->getContentSize().width, this->_spr->getContentSize().height, Texture2D::PixelFormat::RGBA8888);

this->_renderTexture->ignoreAnchorPointForPosition(true);

this->_renderTexture->setPosition(Vec2(400, 200));

this->_renderTexture->setAnchorPoint(Point::ZERO);

this->addChild(this->_renderTexture, 0, 1);

    return true;

}

bool HelloWorld::onTouchBegan(Touch *pTouch, Event *pEvent)

{

bool isTouched = false;

Point touchPoint = pTouch->getLocationInView();

Point glPoint = Director::sharedDirector()->convertToGL(touchPoint);

if (this->_spr->boundingBox().containsPoint(glPoint)) {

       Color4B color4B = { 0, 0, 0, 0 };

       Point nodePos = this->_spr->convertTouchToNodeSpace(pTouch);

       unsigned int x = nodePos.x;

       unsigned int y = this->_spr->getContentSize().height - nodePos.y;

       Point point = this->_spr->getPosition();

       //开始准备绘制 

       this->_renderTexture->begin();

       //绘制使用的临时精灵，与原图是同一图片 

       Sprite* pTempSpr = Sprite::createWithSpriteFrame(this->_spr->displayFrame());

       pTempSpr->setPosition(Vec2(pTempSpr->getContentSize().width / 2, pTempSpr->getContentSize().height / 2));

       //绘制 

       pTempSpr->visit();

       //结束绘制 

       this->_renderTexture->end();

       //通过画布拿到这张画布上每个像素点的信息，封装到Image中 

       Image* pImage = this->_renderTexture->newImage();

       //获取像素数据 

       unsigned char* data_ = pImage->getData();

       unsigned int *pixel = (unsigned int *)data_;

       pixel = pixel + (y * (int)pTempSpr->getContentSize().width) * 1 + x * 1;

       //R通道 

       color4B.r = *pixel & 0xff;

       //G通道 

       color4B.g = (*pixel >> 8) & 0xff;

       //B通过 

       color4B.b = (*pixel >> 16) & 0xff;

       //Alpha通道，输出查看alpha值

       color4B.a = (*pixel >> 24) & 0xff;

       log("alpha = %d", color4B.a);

       if (color4B.a > 50) {

            isTouched = true;

       }

       else {

            isTouched = false;

       }

}

return isTouched;

}

当点击中间和周围没有像素的位置时，打印出的log显示

当点击有像素的位置时，打印出的log显示

点击空白区域时透明通道是0，点击有像素的位置时会显示大于1-255；

春秋工作室  供稿