unit 286 Edge 
.386

assume ds:@code,cs:@code
NoJumps 

Extrn C2G:Byte, G2C:Byte, EdgeSqrt:Byte 

Procedure Far EdgeArea x, y, w, h, S, T
   imul di,y,320 
   add  di,x 
   mov  fs,S
   mov  es,T
   cld 

   $Do 
      mov  si,w
   
      Even       
      $Do 
         mov  bx,offset C2G 
         xor  ax,ax
      
         mov  al,fs:[di-320-1]
         xlat
         mov  dx,ax
         mov  cx,ax
         neg  cx 
      
         mov  al,fs:[di-320]
         xlat
         add  dx,ax
         add  dx,ax
      
         mov  al,fs:[di-320+1]
         xlat
         add  dx,ax
         add  cx,ax 
      
         mov  al,fs:[di-1]
         xlat
         sub  cx,ax 
         sub  cx,ax 
      
         mov  al,fs:[di+1]
         xlat
         add  cx,ax
         add  cx,ax
      
         mov  al,fs:[di+320-1]
         xlat
         sub  dx,ax
         sub  cx,ax 
      
         mov  al,fs:[di+320]
         xlat
         sub  dx,ax
         sub  dx,ax
      
         mov  al,fs:[di+320+1]
         xlat
         sub  dx,ax
         add  ax,cx 
      
         sar  ax,2 
         imul al
         sar  dx,2             
         imul dx,dx 
         add  ax,dx
         shr  ax,5

         mov  bx,offset EdgeSqrt
         xlat 
          
         stosb
      
         dec  si
      $EndDo =0
   
      sub  di,w
      add  di,320
   
      dec  h
   $EndDo =0 
EndProc