draw rectangle on LCD

hello,

this is modified part of camtest.cpp
this is for drawing rectangle on picture fetched from cmos sensor.
but only its horizontal lines, has plotted truly; vertical algorithm leads
to plotting slope line!!!
where is the problem?


//LineLen = 640 (pixels) x 2 (bytes)
//Height = 512 (pixels)
//count=Size=LineLen x Height (bytes)
bool FetchPicture() const {
  int count = ::read(fd, Addr, Size);
  if (count not_eq Size) {
     throw TError("error in fetching picture from video");
   }
   //new added code: draw rectangular
   int i=0;
   for(int c=0;c<count;c+=2){
      //horizontal lines : "truly draws horizontal line"
      if((c>=LineLen*Height/4+LineLen/3)&&
         (c<=LineLen*Height/4+LineLen*2/3)) 
              {*(Addr+c)=255;*(Addr+c+1)=255;} else
      if((c>=LineLen*Height*3/4+LineLen/3)&&
         (c<=LineLen*Height*3/4+LineLen*2/3)) 
              {*(Addr+c)=255;*(Addr+c+1)=255;}
      //vertical lines : "but only draws slope line !!!!!!!!!!!!!!"
      i+=2; if(i>LineLen){i=0;}
      if((i==LineLen*2/4)){*(Addr+c)=255;*(Addr+c+1)=255;}
    }
    return true;
 }

Hi
 Try bellow logic.....

static void Glib_FilledRectangle(int x1,int y1,int x2,int y2,int color)
{
    int i;

    for(i=y1;i<=y2;i++)
  Glib_Line(x1,i,x2,i,color);
}
static void Glib_Line(int x1,int y1,int x2,int y2,int color)
{
  int dx,dy,e;
  dx=x2-x1; 
  dy=y2-y1;
    
  if(dx>=0)
  {
    if(dy >= 0) // dy>=0
    {
      if(dx>=dy) // 1/8 octant
      {
        e=dy-dx/2;
        while(x1<=x2)
        {
          PutPixel(x1,y1,color);
          if(e>0){y1+=1;e-=dx;}  
          x1+=1;
          e+=dy;
        }
      }
      else    // 2/8 octant
      {
        e=dx-dy/2;
        while(y1<=y2)
        {
          PutPixel(x1,y1,color);
          if(e>0){x1+=1;e-=dy;}  
          y1+=1;
          e+=dx;
        }
      }
    }
    else       // dy<0
    {
      dy=-dy;   // dy=abs(dy)

      if(dx>=dy) // 8/8 octant
      {
        e=dy-dx/2;
        while(x1<=x2)
        {
          PutPixel(x1,y1,color);
          if(e>0){y1-=1;e-=dx;}  
          x1+=1;
          e+=dy;
        }
      }
      else    // 7/8 octant
      {
        e=dx-dy/2;
        while(y1>=y2)
        {
          PutPixel(x1,y1,color);
          if(e>0){x1+=1;e-=dy;}  
          y1-=1;
          e+=dx;
        }
      }
    }  
  }
  else //dx<0
  {
    dx=-dx;    //dx=abs(dx)
    if(dy >= 0) // dy>=0
    {
      if(dx>=dy) // 4/8 octant
      {
        e=dy-dx/2;
        while(x1>=x2)
        {
          PutPixel(x1,y1,color);
          if(e>0){y1+=1;e-=dx;}  
          x1-=1;
          e+=dy;
        }
      }
      else    // 3/8 octant
      {
        e=dx-dy/2;
        while(y1<=y2)
        {
          PutPixel(x1,y1,color);
          if(e>0){x1-=1;e-=dy;}  
          y1+=1;
          e+=dx;
        }
      }
    }
    else       // dy<0
    {
      dy=-dy;   // dy=abs(dy)

      if(dx>=dy) // 5/8 octant
      {
        e=dy-dx/2;
        while(x1>=x2)
        {
          PutPixel(x1,y1,color);
          if(e>0){y1-=1;e-=dx;}  
          x1-=1;
          e+=dy;
        }
      }
      else    // 6/8 octant
      {
        e=dx-dy/2;
        while(y1>=y2)
        {
          PutPixel(x1,y1,color);
          if(e>0){x1-=1;e-=dy;}  
          y1-=1;
          e+=dx;
        }
      }
    }  
  }
}
static void PutPixel(U32 x,U32 y,U32 c)
{
  if ( (x < SCR_XSIZE_TFT_320240) && (y < SCR_YSIZE_TFT_320240) )
  LCD_BUFER[(y)][(x)] = c;
}