cocos2dx实现自定义图形橡皮擦功能 不是利用ClippingNode

好了这里我先上代码

首先定义这个函数

void HelloWorld::changeDatas(Image *image,Image * image1,Point point)
{
	auto data = image->getData();//橡皮擦数据头指针
	auto data1 = image1->getData();//被擦除数据头指针
	auto size = Director::getInstance()->getVisibleSize();
	int pha = 3;
	if (image->hasAlpha())//判断是否有Alpha通道
	{
		pha = 4;
	}

	for (int x = 0; x < image->getWidth(); ++x)
	{
		for (int y = 0; y < image->getHeight(); ++y)
		{
			/*下面是获取rgb颜色值 这里说明一下   
		    data是指向数据的头指;指针指向数据的排列方式是 data 0~3 rgba data 4~7 rgba
			所以没有Alpha通道 的排列方式是  data 0~2  rgb  data 3~5  rgb
			*/
			unsigned char *pixel = data + (x + y * image->getWidth()) * pha;//遍历每个像素点的rgb
			unsigned int r = (unsigned int)*pixel;
			unsigned int g = (unsigned int)*(pixel + 1);
			unsigned int b = (unsigned int)*(pixel + 2);
			unsigned int a = (unsigned int)*(pixel + 3);

			if (r != 0 || g != 0 || b != 0 || a != 0)//如果该点有颜色就将被剪裁区域的颜色替换成无色
			{
				Point changep = Point(size.width/2,size.height-size.height/2);//因为Opengl的坐标在左上角所以做坐标转换;这里应该把被剪裁区域的图坐标转换成OPENGL
				Point changep1 = Point(changep.x - image1->getWidth() / 2,changep.y - image1->getHeight() / 2);

				int c = x + point.x - changep1.x - image->getWidth() / 2;
				int d = y + point.y - changep1.y - image->getHeight() / 2;

				if (c>0&&d>0&&c < image1->getWidth() && d <image1->getHeight())
				{
					int pha1 = 3;
					if (image1->hasAlpha())
					{
						pha1 = 4;
					}
					unsigned char *pixel1 = data1 + (c + d * image1->getWidth()) * pha1;
					*pixel1 = 0;//数据修改
					*(pixel1 + 1) = 0;
					*(pixel1 + 2) = 0;
		
				}
			}

		}
	}


}

然后在初始化方法里

auto CliperImage = new Image();//创建一个需要剪裁的Image

	CliperImage->initWithImageFile("HelloWorld.png");
	auto image = new Image();//创建一个橡皮擦Image

	image->initWithImageFile("123.png");
	auto text = new Texture2D();
	text->initWithImage(CliperImage);
	auto sp = Sprite::createWithTexture(text);
	sp->setPosition(visibleSize.width/2,visibleSize.height/2);
	this->addChild(sp,33);//通过不停的更新这个SP来实现涂擦效果 也可以认为更新了CliperImage的DATA来实现

	/*创建监听事件*/
	auto linstener = EventListenerTouchOneByOne::create();

	linstener->onTouchBegan = [this](Touch *touch,Event *event)
	{
			return true;
	
	
	};
	linstener->onTouchMoved = [this,CliperImage,image](Touch *touch,Event *event)
	{
		auto size = Director::getInstance()->getVisibleSize();
		this->removeChildByTag(33);
		changeDatas(image,Point(touch->getLocation().x,size.height - touch->getLocation().y));
		auto text1 = new Texture2D();
		text1->initWithImage(CliperImage);
		auto sp = Sprite::createWithTexture(text1);
		sp->setPosition(size.width / 2,size.height / 2);
		addChild(sp,33);
		
	};

	linstener->onTouchEnded = [this,Event *event)
	{  
		auto size = Director::getInstance()->getVisibleSize();
		this->removeChildByTag(33);
		changeDatas(image,size.height - touch->getLocation().y));
	    auto text1 = new Texture2D();
		text1->initWithImage(CliperImage);
		auto sp = Sprite::createWithTexture(text1);
		sp->setPosition(size.width/2,size.height/2);
		addChild(sp,33);
	};

	_eventdispatcher->addEventListenerWithSceneGraPHPriority(linstener,this);

好了我们来看下效果同样的123.png是这个

效果图

其实原理就是通过修改这张图的二进制文件数据来实现擦涂效果；

不像我上一篇介绍的ClippingNode一样可以添加很多精灵进行裁剪；