说明
ErasableLayer是一个可擦除的Layer，可实现类似橡皮擦、刮奖等效果。原理是通过颜色混合实现的。关于颜色混合可查看这篇文章（点击查看）。
测试环境：Cocos2d-x v3.3、Cocos2d-x v3.5
源码下载：ErasableLayer.zip
源码
ErasableLayer.cpp
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#include "ErasableLayer.h"ErasableLayer::ErasableLayer() :isErasable_(true){}ErasableLayer::~ErasableLayer(){ CC_SAFE_RELEASE(layer_); CC_SAFE_RELEASE(erasa_);} ErasableLayer* ErasableLayer::create(const char* layerPath, const char* erasaPath){ CCSprite* layer = CCSprite::create(layerPath); CCSprite* erasa = CCSprite::create(erasaPath); ErasableLayer* ret = new ErasableLayer; if (ret->init(layer, erasa)) { ret->autorelease(); return ret; } delete ret; return nullptr;}ErasableLayer* ErasableLayer::create(Node* layer, Sprite* erasa){ ErasableLayer* ret = new ErasableLayer; if (ret->init(layer, erasa)) { ret->autorelease(); return ret; } delete ret; return nullptr;}ErasableLayer* ErasableLayer::create(Node* layer, const char* erasaPath){ CCSprite* erasa = CCSprite::create(erasaPath); ErasableLayer* ret = new ErasableLayer; if (ret->init(layer, erasa)) { ret->autorelease(); return ret; } delete ret; return nullptr;}ErasableLayer* ErasableLayer::create(const char* layerPath, Sprite* erasa){ CCSprite* layer = CCSprite::create(layerPath); ErasableLayer* ret = new ErasableLayer; if (ret->init(layer, erasa)) { ret->autorelease(); return ret; } delete ret; return nullptr;}bool ErasableLayer::init(Node *layer, Sprite* erasa){ if (!Layer::init()) { return false; } layer_ = layer; erasa_ = erasa; layer_->retain(); erasa_->retain(); this->setContentSize(layer_->getContentSize()); // 设置颜色混合模式 BlendFunc erasaBf = { GL_ZERO, GL_ONE_MINUS_SRC_ALPHA }; //源因子：值为0，橡皮擦颜色为透明；目标因子：目标颜色透明度减去源颜色的透明度 erasa_->setBlendFunc(erasaBf); auto size = layer_->getContentSize(); rt_ = RenderTexture::create(size.width, size.height); rt_->setAnchorPoint(Vec2(0, 0)); rt_->setPosition(Vec2(size.width/2, size.height/2)); this->addChild(rt_); clear(); schedule(CC_SCHEDULE_SELECTOR(ErasableLayer::tick)); // 触摸事件 auto listener = EventListenerTouchOneByOne::create(); listener->onTouchBegan = CC_CALLBACK_2(ErasableLayer::onTouchBegan, this); listener->onTouchMoved = CC_CALLBACK_2(ErasableLayer::onTouchesMoved, this); listener->onTouchEnded = CC_CALLBACK_2(ErasableLayer::onTouchEnded, this); _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this); listener->setSwallowTouches(false); return true;}void ErasableLayer::tick(float){ if (!isErasable_) { return; } // 设置源颜色alpha值为最大值，目标颜色alpha值减去源颜色alpha值后就为0了，混合出来的效果就变透明了，这样就实现了橡皮擦效果了。 erasa_->setOpacity(255); // 更新RenderTexture rt_->begin(); // 绘制 erasa_->visit(); rt_->end();}void ErasableLayer::clear(){ layer_->setAnchorPoint(Vec2(0, 0)); layer_->setPosition(Vec2(0, 0)); rt_->begin(); layer_->visit(); rt_->end();}void ErasableLayer::setErasable(bool flag){ isErasable_ = flag;}bool ErasableLayer::onTouchBegan(Touch* touch, Event *event){ erasa_->setPosition(this->convertToNodeSpace(touch->getLocation())); return true;}void ErasableLayer::onTouchesMoved(Touch* touch, Event *event){ erasa_->setPosition(this->convertToNodeSpace(touch->getLocation()));}void ErasableLayer::onTouchEnded(Touch* touch, Event *event){ erasa_->setPosition(this->convertToNodeSpace(touch->getLocation()));} |
ErasableLayer.h
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#ifndef __ERASABLELAYER_H__#define __ERASABLELAYER_H__#include "cocos2d.h"USING_NS_CC;// 可擦除的Layerclass ErasableLayer :public Layer{ public: // 创建ErasableLayer //1.遮罩层 //2.橡皮擦（可以是Sprite或者纹理的路径） static ErasableLayer* create(const char* layerPath, const char* erasaPath); static ErasableLayer* create(Node *layer, Sprite* erasa); static ErasableLayer* create(Node *layer, const char* erasaPath); static ErasableLayer* create(const char* layerPath, Sprite* erasa); // 还原 void clear(); // 是否可擦除 void setErasable(bool); bool onTouchBegan(Touch* touch, Event *event); void onTouchesMoved(Touch* touch, Event *event); void onTouchEnded(Touch* touch, Event *event); protected: ErasableLayer(); ~ErasableLayer(); bool init(Node *layer, Sprite* erasa); void tick(float); private: Node* layer_; Sprite* erasa_; bool isErasable_; RenderTexture* rt_;};#endif |
调用示例代码.cpp
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// 调用示例// 遮罩层auto maskLayer = LayerColor::create(Color4B(0,0,255,200));maskLayer->setContentSize(sprite->getContentSize());// 创建可擦除的Layerauto layer = ErasableLayer::create(maskLayer, "eraser.png");layer->setPosition(Vec2(visibleSize.width / 4, visibleSize.height / 4));this->addChild(layer); |
这里创建了一个蓝色的LayerColor，并擦除该Layer。
http://cn.cocos2d-x.org/tutorial/show?id=2790