Line Clipping Program Using C Programming

🎯 Introduction

Line clipping is an essential technique used in computer graphics to determine which portions of a line lie within a specified window or viewport. The Cohen-Sutherland algorithm is one of the most widely used line clipping algorithms. It efficiently identifies and discards the line segments outside the specified window, thus optimizing rendering and improving visual performance. In this blog post, we will update and explain a C program that implements the Cohen-Sutherland line clipping algorithm. We will provide a detailed explanation of the algorithm, its concept, and walk through the code to understand how it clips lines efficiently.

🎯 Concept: Cohen-Sutherland Line Clipping Algorithm

The Cohen-Sutherland line clipping algorithm is a simple and efficient technique to clip a line against a rectangular clipping window. It divides the 2D space into nine regions using four boundary lines: left, right, top, and bottom. These regions are determined by assigning codes to each point (endpoints of the line) based on their relative positions with respect to the clipping window.

The algorithm works as follows:

Assign a four-bit binary code to each endpoint of the line based on its position relative to the clipping window. The four bits represent the left, right, top, and bottom regions.

Check if both endpoints have a zero code (inside the window). If so, the line is completely inside the window, and no further processing is required.

If both endpoints have a non-zero code and share at least one common bit value (AND operation of the codes is not zero), the line is entirely outside the window, and it can be rejected.

If the above conditions are not met, perform the Cohen-Sutherland clipping algorithm to find the intersection points of the line with the window boundaries and update the line endpoints accordingly.

🎯 Line Clipping Program Program





#define Round(val)((int)(val+.5))

int maxx, maxy, miny, minx;

void main() {

   int gd = DETECT, gm;

   void clipping(int xa, int ya, int xb, int y);

   int xa, xb, ya, yb;

   printf("Enter the window coordination");

   scanf("%d%d%d%d", &minx, &maxy, &maxx, &miny);

   printf("Enter the two and points for the line");

   scanf("%d%d%d%d", &xa, &ya, &xb, &yb);

   initgraph(&gd, &gm, "");

   rectangle(minx, miny, maxx, maxy);

   line(xa, ya, xb, yb);




void clipping(int xa, int ya, int xb, int yb) {

   int Dx = xb - xa, Dy = yb - ya, steps, k;

   int visible1 = 0, visible2 = 0;

   float xin, yin, x = xa, y = ya;

   if (abs(Dx) > abs(Dy))

      steps = abs(Dx);


      steps = abs(Dy);

   xin = Dx / (float) steps;

   yin = Dy / (float) steps;

   putpixel(Round(x), Round(y), 2);

   for (k = 0; k < steps; k++) {

      x += xin;

      y += yin;

      if ((y > miny && y < maxx)) {

         visible1 = 1;

         putpixel(Round(x), Round(y), 2);

      } else

         visible2 = 1;


   if (visible1 == 0)

      outtextxy(20, 200, "complextely visible");

   if (visible1 == 1 && visible2 == 1)

      outtextxy(20, 20, "partialy visible");

   if (visible1 == 1 && visible2 == 0)

      outtextxy(20, 20, "completly visible");


🎯 Detailed Explanation

The program starts by defining the necessary header files (stdio.h, conio.h, graphics.h, and math.h) and a macro Round to round off floating-point numbers to the nearest integer.

🎯 Summary

In this blog post, we covered the Cohen-Sutherland line clipping algorithm, a fundamental technique in computer graphics for efficiently determining which portions of a line lie within a specified window. We updated and explained a C program that implements the algorithm. The code prompts the user to input the window coordinates and line endpoints, and it then uses graphics functions to draw the window and the original line. The clipping function efficiently clips the line and displays appropriate messages based on visibility. By understanding the Cohen-Sutherland algorithm, you now have a powerful tool to efficiently handle line clipping tasks in your own graphics projects.

🎯 Key Points