如何利用差分方法实现虚拟选择菜单

如何利用差分方法实现虚拟选择菜单

一些摄像头程序实现了用差分方法来选择菜单，就是你不断用运动的物体干扰监测目标，它会出现进度条，直到选中，例如camgoo,实际上它实现起来却非常的简单。不过它的作用却是很大。

下图绿色表示选择的进度，

第一步准备

//颜色转化
cvCvtColor( image, grey, CV_BGR2GRAY );    
//差分
cvAbsDiff( grey,prev_grey, abs_img );

//清理低的值，这样抗干扰强
cvThreshold( abs_img, abs_img, 30, 255, CV_THRESH_BINARY);

第二步：
//定义命中器的结构
typedef struct hit_chooser
{ 
    float Perc_x;
    float Perc_y;
    float Perc_width;
    float Perc_height;
    int hit_count;
    bool isUse;
} hit_chooser;

//初始化数据，定义一个监视区域
hit_chooser Hit_Objects[WW_MAX_HIT_COUNT];
Hit_Objects[0].isUse  =true;
Hit_Objects[0].Perc_x   = 0.7; 
Hit_Objects[0].Perc_y   = 0.6;
Hit_Objects[0].Perc_width = 0.1;
Hit_Objects[0].Perc_height = 0.1;
Hit_Objects[0].hit_count = 0;

第三步，在需要检测的地方加入 getHitCounts(Hit_Objects);

WW_RETURN HumanMotion::getHitCounts(hit_chooser *Hit_Objects)
/*************************************************
  Function:
  Description:  利用差分统计命中数目，返回该区域的命中次数     
  Date:   2006－7－24
  Author:  
  Input:                       
  Output:        
  Return:        
  Others:         
*************************************************/
{
 const int w = abs_img->width;
 const int h = abs_img->height;
 float counter = 0;

 for(int i=0;i<WW_MAX_HIT_COUNT;i++)
 {
  if(Hit_Objects[i].isUse)
  {
   if(Hit_Objects[i].hit_count<100)
   {
    int x = Hit_Objects[i].Perc_x * w;
    int y = Hit_Objects[i].Perc_y * h;
    int Perc_width = Hit_Objects[i].Perc_width * w;
    int Perc_height = Hit_Objects[i].Perc_height * h;
    cvSetImageROI( abs_img, cvRect( x, y,Perc_width,Perc_height));
    int num  = cvCountNonZero(abs_img);
    cvResetImageROI(abs_img);
    if(num > 10)
    {     
     Hit_Objects[i].hit_count+=2; //升值比降值快一倍
    }
    else
    {
     if(Hit_Objects[i].hit_count>0)
     {
      Hit_Objects[i].hit_count --;
     }
    }
   }
  }
 }
 return WW_OK;
}
 
第四步显示出来

void showHitObject(void)
{

  for(int i=0;i<WW_MAX_HIT_COUNT;i++)
  {
   if(Hit_Objects[i].isUse)
   {
    //draw a circle
    glPushMatrix();
    glTranslatef(Hit_Objects[i].Perc_x*room_size/3 , 0.0,Hit_Objects[i].Perc_y*room_size/2);
    glRotatef(90,1,0,0);
    glColor3f(1,1,1);
    dsDrawTours(0.2,0.3,45,45,false);   

    if(Hit_Objects[i].hit_count>0 && Hit_Objects[i].hit_count<100)
    {
     //show hit  
     int hit = (float)Hit_Objects[i].hit_count/100*45;    
     glTranslatef(0.0, 0.0,0.1);
     dsDrawTours(0.2,0.3,45,hit,true);
    }

    if(Hit_Objects[i].hit_count>=100)
    {
     //show full
     glColor3f(0,1,0);
     glTranslatef(0.0, 0.0,0.1);
     dsDrawTours(0.2,0.3,45,45,false);
    }
    glPopMatrix();
   }
  }

}

//显示圆环
void dsDrawTours(float inRadio,float ExRadio,int numc,int endnumc,bool needcolor)
{
   int i;
   double s, twopi,sinA,cosA,x,y;

   twopi = 2 * 3.14;
   for (i = 0; i <endnumc; i++)
   {  
      glBegin(GL_QUAD_STRIP);    
   {
       
   s = i;
   if(needcolor) glColor3f(0,s/numc/2+0.2,0);

   s= s/numc*twopi;
            sinA = sin(s);
            cosA = cos(s);
            x = inRadio * sinA;
            y = inRadio * cosA;
            glVertex2f(x, y);

            x = ExRadio * sinA;
            y = ExRadio * cosA;
            glVertex2f(x, y);

   s = i+1;
   s= s/numc*twopi;
            sinA = sin(s);
   cosA = cos(s);
            x = inRadio * sinA;
            y = inRadio * cosA;
            glVertex2f(x, y);

            x = ExRadio * sinA;
            y = ExRadio * cosA;
            glVertex2f(x, y);  

      }
      glEnd();
   }
}