typedef irr::video::SColor TSColor;
typedef irr::video::ITexture TITexture;
typedef irr::core::dimension2d<s32> TiDim2D;
...

video::E_DRIVER_TYPE devDriver = video::EDT_OPENGL; //geht mit EDT_DIRECT3Dx
irrDevice=createDevice(devDriver,TiDim2D(800,600),32,false);
videoDriver=irrDevice->getVideoDriver();

TITexture *g_tex=videoDriver->addTexture(TiDim2D(256,192),"Tex1",video::ECF_A8R8G8B8);

void setTexPixel(TITexture *pTex,void *pData,int x, int y,TSColor pColor)
{
   if(pTex!=NULL)
   {
      if(pTex->getColorFormat()==video::ECF_A8R8G8B8)
      {
         unsigned int *data32 =(unsigned int*) pData;
         data32[x+y*pTex->getSize().Width]=pColor.color;
      }else{
         printf("Unknown color format.\n");
      }
   }
};

void *tdata=g_tex->lock();
   setTexPixel(g_tex,tdata,x,y,TSColor(0,255,255,255)));
g_tex->unlock();

videoDriver->beginScene(true,false,TSColor(0,0,0,200));
   videoDriver->draw2DImage(g_tex,TiRect(0,0,800,600),TiRect(0,0,256,192));
videoDriver->endScene();