// before (in the class constructor)
	m_mask = new unsigned[(m_picture->w*m_picture->h)/32 + 2]; 
	for (int i = 0; i < (m_picture->w*m_picture->h)/32 + 2 ; i++)m_mask = 0;


void CPicture::CreateMask(){
	// creer le mask de bit.
	//attention, superbe arithmetique de pointeur.
	unsigned* p = m_mask;
	(*p) += 1;
	int h  = m_picture->h;
	int w  = m_picture->w;
	unsigned int colorkey = m_picture->format->colorkey;
	unsigned int Pixel;
	int cpt = 0;
	
	SDL_LockSurface(m_picture);
	for (int j = 0; j<h; j++){
		for (int i = 0; i<w; i++){
			Pixel = GetPixel(i,j);// recupere le pixel i,j
			switch (cpt){
				case 0 : if(Pixel != colorkey) (*p) |= 0x8; break;
				case 1 : if(Pixel != colorkey) (*p) |= 0x4; break;
				case 2 : if(Pixel != colorkey) (*p) |= 0x2; break;
				case 3 : if(Pixel != colorkey) (*p) |= 0x1; break;
			}
			cpt++;	
			if(cpt == 4){(*p)+=1; cpt = 0;}		
		}
	SDL_UnlockSurface(m_picture);
	}
}