我的环境是cocos2dx 2.x的版本
【CCRenderTexture】
CCRenderTexture这个动态纹理类，顾名思义就是可以动态创建纹理图片。
屏幕截图主要步骤：
> 开始截图：render->begin();
> 遍历场景：scene->visit();
> 结束截图：render->end();
> 保存截图：render->saveToFile(string& filename, Image::Format format);
其中Image::Format为图片格式，可以保存为PNG、或JPG两种格式。
即：Image::Format::PNG、Image::Format::JPG。
首先是截整个屏幕（CCDirector.cpp中）：
saveToDCIM函数，找个目录，然后找到一个没用过的名字开始saveScreenShot
1 void CCDirector::saveToDCIM()
2 {
3 char bufferName[256];
4
5 for (int i = 0;i<999999;i++)
6 {
7 std:string filedir = "";
8 #if CC_TARGET_PLATFORM == CC_PLATFORM_ANDROID
9 filedir = std::string(SDKInterface::getExternalStoragePath()) +"/Screenshots";
10 #else
11 filedir = CCFileUtils::sharedFileUtils()->getWritablePath() +"/Screenshots";
12 #endif
13 memset(bufferName,0,sizeof(bufferName));
14 sprintf(bufferName,"/SCREENSHOT_%d.png",i);
15 std::string filename = filedir + std::string(bufferName);
16 if(!CCFileUtils::sharedFileUtils()->isFileExist(filename))
17 {
18 CCLog("ScreenShoot");
19 createDirectory(filedir.c_str());
20 saveScreenshot(filename);
21 return;
22 }
23 }
24 }
这是实际干活的函数：
1 void CCDirector::saveScreenshot( const std::string& fileName)
2 {
3 CCScene* temp = CCDirector::sharedDirector()->getRunningScene();
4 if (temp)
5 {
6 CCSize winSize = CCDirector::sharedDirector()->getWinSize();
7 CCRenderTexture* rt = CCRenderTexture::create(winSize.width, winSize.height);
8 rt->begin();
9 temp->visit();
10 rt->end();
11 rt->saveToFile(fileName.c_str());
12 CCLog(fileName.c_str());
13 }
14 }
然后是截取屏幕的某一个部分，cocos2dx 3.x的版本里可以直接用这个函数：
2.x版本的怎么办呢？用得到的全屏截图rt的一部分RECT创建Sprite，然后在visit该Sprite，获得第二张截图rt2（比较懒，肯定不是最好的方法，欢迎指点）：
1 void CCDirector::renderTexturePartImpl(int x, int y, int width, int height, const std::string& fileName)
2 {
3 CCScene* temp = CCDirector::sharedDirector()->getRunningScene();
4 if (temp)
5 {
6 CCSize winSize = CCDirector::sharedDirector()->getWinSize();
7 CCRenderTexture* rt = CCRenderTexture::create(winSize.width, winSize.height);
8 rt->beginWithClear(0,0,0,0,0);
9 temp->visit();
10 rt->endToLua();
11
12 CCRenderTexture* rt2 = CCRenderTexture::create(width, height);
13 CCSprite* spr = CCSprite::createWithTexture(rt->getSprite()->getTexture(), CCRect(x, y, width, height));
14 spr->setAnchorPoint(CCPoint(0,0));
15 spr->setPosition(CCPoint(0,0));
16 spr->setFlipY(true);
17 rt2->beginWithClear(0,0,0,0,0);
18 spr->visit();
19 rt2->endToLua();
20 rt2->saveToFile(fileName.c_str());
21 CCLog(fileName.c_str());
22 }
23 }