图片mask混合

Texture2D* openImage(const char* jpgFile,const char* maskFile)
{
    std::string name = jpgFile;
    name.erase(name.length()-4,4);
    std::string outname = name + ".png";

    auto ret = Director::getInstance()->getTextureCache()->getTextureForKey(name);
    if(ret)
        return ret;
    auto _img = new Image();
    auto _jpg = new Image();
    auto _mask = new Image();
    do
    {
        if(!_jpg->initWithImageFile(jpgFile))
            break;
        if(!_mask->initWithImageFile(maskFile))
            break;
        auto _color = _jpg->getData();
        auto _alpha = _mask->getData();
        auto _w = _jpg->getWidth();
        auto _h = _jpg->getHeight();
        auto _l = _jpg->getDataLen();
        auto _out = new unsigned char[_l*4];
        for(int idx = 0; idx < _l ; idx++)
        {
            _out[idx*4]      = _color[idx*3];
            _out[idx*4+1] = _color[idx*3+1];
            _out[idx*4+2] = _color[idx*3+2];
            _out[idx*4+3] = _alpha[idx];
        }
        _img->initWithRawData(_out,_l*4,_w,_h,4);
        ret = Director::getInstance()->getTextureCache()->addImage(_img,name);
        _img->saveToFile(outname, false);

        CC_SAFE_DELETE(_out);
        break;
    } while (1);

    CC_SAFE_DELETE(_img);
    CC_SAFE_DELETE(_jpg);
    CC_SAFE_DELETE(_mask);
    return ret;
} 

http://malideveloper.arm.com/cn/develop-for-mali/sample-code/etcv1-texture-compression-and-alpha-channels/