//---------------------------------------------------------------------------
//Algorytm Cohena-Sutherlanda
//(c) 2009 by Tomasz Lubinski
//www.algorytm.org

#include <vcl.h>
#pragma hdrstop

#include "Cohen_Sutherland.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Label6Click(TObject *Sender)
{
 ShellExecute(Application->Handle,
             "open",
             "http://www.algorytm.org",
             NULL,
             NULL,
             SW_NORMAL);
}

#define LEFT 80
#define RIGHT 420
#define TOP 80
#define BOTTOM 320

unsigned char calcRegCode(int x, int y)
{
   unsigned char result = 0;
   if (x < LEFT)   result |= 0x1;
   if (x > RIGHT)  result |= 0x2;
   if (y > BOTTOM) result |= 0x4;
   if (y < TOP)    result |= 0x8;

   return result;
}

//---------------------------------------------------------------------------
void __fastcall TForm1::Cohen_Sutherland(int x1, int y1, int x2, int y2)
{
   unsigned char rcode1, rcode2, rcode;
   int x, y;

   /* Algorytm Cohena-Sutherlanda */
   /* 1. Zakoduj końce odcinka zgodnie z kodami obszarów */
   rcode1 = calcRegCode(x1, y1);
   rcode2 = calcRegCode(x2, y2);
   /* 2. Jeżeli iloczyn logiczny (AND) tych kodów <>0,
      to odcinek może być pominięty (w całości poza
      oknem) - zaznacz go na czerwono */
   if (rcode1 & rcode2)
   {
      Image1->Canvas->Pen->Color = clRed;
      Image1->Canvas->MoveTo(x1, y1);
      Image1->Canvas->LineTo(x2, y2);
   }
      /* 3. Jeżeli suma logiczna (OR)tych kodów = 0,
         to odcinek w całości mieści się w okienku
         - zaznacz go na zielono */
   else if ((rcode1 | rcode2) == 0)
   {
      Image1->Canvas->Pen->Color = clGreen;
      Image1->Canvas->MoveTo(x1, y1);
      Image1->Canvas->LineTo(x2, y2);
   }
   else
   {
      /* pozostale przypadki - przeciecie z krawedzia okna */
      do
      {
         if (rcode1 != 0)
         {
            rcode = rcode1;
         }
         else
         {
            rcode = rcode2;
         }

         /* pozostale przypadki - przeciecie z krawedzia okna */
         if (rcode & 0x1)
         {
            y = y1+(y2-y1)*(LEFT-x1)/(x2-x1);
            x = LEFT;
         }
         else if (rcode & 0x2)
         {
            y = y1+(y2-y1)*(RIGHT-x1)/(x2-x1);
            x = RIGHT;
         }
         else if (rcode & 0x4)
         {
            x = x1+(x2-x1)*(BOTTOM-y1)/(y2-y1);
            y = BOTTOM;
         }
         else if (rcode & 0x8)
         {
            x = x1+(x2-x1)*(TOP-y1)/(y2-y1);
            y = TOP;
         }

         if (rcode == rcode1)
         {
            Image1->Canvas->Pen->Color = clYellow;
            Image1->Canvas->MoveTo(x1, y1);
            Image1->Canvas->LineTo(x, y);
            x1 = x;
            y1 = y;
            rcode1 = calcRegCode(x1, y1);
         }
         else
         {
            Image1->Canvas->Pen->Color = clYellow;
            Image1->Canvas->MoveTo(x2, y2);
            Image1->Canvas->LineTo(x, y);
            x2 = x;
            y2 = y;
            rcode2 = calcRegCode(x2, y2);
         }
      } while ((rcode1 & rcode2) == 0 && (rcode1 | rcode2) != 0);

      if ((rcode1 | rcode2) == 0)
      {
         Image1->Canvas->Pen->Color = clBlue;
         Image1->Canvas->MoveTo(x1, y1);
         Image1->Canvas->LineTo(x2, y2);
      }
      else
      {
         Image1->Canvas->Pen->Color = clYellow;
         Image1->Canvas->MoveTo(x1, y1);
         Image1->Canvas->LineTo(x2, y2);
      }
   }
}


void __fastcall TForm1::Button1Click(TObject *Sender)
{
int i, x1, y1, x2, y2;

/* wyczysc wszystko */
Image1->Canvas->Pen->Color = clBlack;
Image1->Canvas->Pen->Width = 2;
Image1->Canvas->Brush->Color = clWhite;
Image1->Canvas->Rectangle(0, 0, Image1->Width, Image1->Height);

/* narysuj okno */
Image1->Canvas->Brush->Color = clLtGray;
Image1->Canvas->Rectangle(LEFT, TOP, RIGHT, BOTTOM);

/* losuj odciniki */
randomize();
for (i=0; i<20; i++)
{
   x1 = random(Image1->Width);
   y1 = random(Image1->Height);
   x2 = x1 + random(200) - 100;
   y2 = y1 + random(200) - 100;

   Cohen_Sutherland(x1, y1, x2, y2);
}
}
//---------------------------------------------------------------------------