Clipping.cpp

#include <bits/stdc++.h>
#include <graphics.h>
#include <gtk/gtk.h>
#include "clipping.h"
using namespace std;

// Global Variables
int xmin, xmax, ymin, ymax;



// This will return the sign required.
int sign(int x)
{
    if (x > 0)
        return 1;
    else
        return 0;
}

// CohenSutherLand LineClipping Algorith As Described in theory.
// This will clip the lines as per window boundries.
void clip(struct lines mylines)
{
    // arrays will store bits
    // Here bits impiles initial Point whereas bite implies end points
    int bits[4], bite[4], i, var;
    // setting color of graphics to be RED
    setcolor(RED);

    // Finding Bits
    bits[0] = sign(xmin - mylines.x1);
    bite[0] = sign(xmin - mylines.x2);
    bits[1] = sign(mylines.x1 - xmax);
    bite[1] = sign(mylines.x2 - xmax);
    bits[2] = sign(ymin - mylines.y1);
    bite[2] = sign(ymin - mylines.y2);
    bits[3] = sign(mylines.y1 - ymax);
    bite[3] = sign(mylines.y2 - ymax);

    // initial will used for initial coordinates and end for final
    string initial = "", end = "", temp = "";

    // convert bits to string
    for (i = 0; i < 4; i++) {
        if (bits[i] == 0)
            initial += '0';
        else
            initial += '1';
    }
    for (i = 0; i < 4; i++) {
        if (bite[i] == 0)
            end += '0';
        else
            end += '1';
    }

    // finding slope of line y=mx+c as (y-y1)=m(x-x1)+c
    // where m is slope m=dy/dx;

    float m = (mylines.y2 - mylines.y1) / (float)(mylines.x2 - mylines.x1);
    float c = mylines.y1 - m * mylines.x1;

    // if both points are inside the Accept the line and draw
    if (initial == end && end == "0000") {
        // inbuild function to draw the line from(x1, y1) to (x2, y2)
        line(mylines.x1, mylines.y1, mylines.x2, mylines.y2);
        return;
    }

    // this will contain cases where line maybe totally outside for partially inside
    else {
        // taking bitwise end of every value
        for (i = 0; i < 4; i++) {

            int val = (bits[i] & bite[i]);
            if (val == 0)
                temp += '0';
            else
                temp += '1';
        }
        // as per algo if AND is not 0000 means line is completely outside hene draw nothing and retrurn
        if (temp != "0000")
            return;

        // Here contain cases of partial inside or outside
        // So check for every boundary one by one
        for (i = 0; i < 4; i++) {
            // if boths bit are same hence we cannot find any intersection with boundary so continue
            if (bits[i] == bite[i])
                continue;
            // Otherwise there exist a intersection

            // Case when initial point is in left xmin
            if (i == 0 && bits[i] == 1) {
                var = round(m * xmin + c);
                mylines.y1 = var;
                mylines.x1 = xmin;
            }
            // Case when final point is in left xmin
            if (i == 0 && bite[i] == 1) {
                var = round(m * xmin + c);
                mylines.y2 = var;
                mylines.x2 = xmin;
            }
            // Case when initial point is in right of xmax
            if (i == 1 && bits[i] == 1) {
                var = round(m * xmax + c);
                mylines.y1 = var;
                mylines.x1 = xmax;
            }
            // Case when final point is in right of xmax
            if (i == 1 && bite[i] == 1) {
                var = round(m * xmax + c);
                mylines.y2 = var;
                mylines.x2 = xmax;
            }
            // Case when initial point is in top of ymin
            if (i == 2 && bits[i] == 1) {
                var = round((float)(ymin - c) / m);
                mylines.y1 = ymin;
                mylines.x1 = var;
            }
            // Case when final point is in top of ymin
            if (i == 2 && bite[i] == 1) {
                var = round((float)(ymin - c) / m);
                mylines.y2 = ymin;
                mylines.x2 = var;
            }
            // Case when initial point is in bottom of ymax
            if (i == 3 && bits[i] == 1) {
                var = round((float)(ymax - c) / m);
                mylines.y1 = ymax;
                mylines.x1 = var;
            }
            // Case when final point is in bottom of ymax
            if (i == 3 && bite[i] == 1) {
                var = round((float)(ymax - c) / m);
                mylines.y2 = ymax;
                mylines.x2 = var;
            }
            // Updating Bits at every point
            bits[0] = sign(xmin - mylines.x1);
            bite[0] = sign(xmin - mylines.x2);
            bits[1] = sign(mylines.x1 - xmax);
            bite[1] = sign(mylines.x2 - xmax);
            bits[2] = sign(ymin - mylines.y1);
            bite[2] = sign(ymin - mylines.y2);
            bits[3] = sign(mylines.y1 - ymax);
            bite[3] = sign(mylines.y2 - ymax);
        } // end of for loop
        // Inialize initial and end to NULL
        initial = "", end = "";
        // Updating strings again by bit
        for (i = 0; i < 4; i++) {
            if (bits[i] == 0)
                initial += '0';
            else
                initial += '1';
        }
        for (i = 0; i < 4; i++) {
            if (bite[i] == 0)
                end += '0';
            else
                end += '1';
        }
        // If now both points lie inside or on boundary then simply draw the updated line
        if (initial == end && end == "0000") {
            line(mylines.x1, mylines.y1, mylines.x2, mylines.y2);
            return;
        }
        // else line was completely outside hence rejected
        else
            return;
    }
}

// Driver Function
void clipping(GtkButton* btn, GtkWidget* win_menu)
{
    /// hide the menu window
    gtk_widget_hide(win_menu);

    int gd = DETECT, gm;

    // Setting values of Clipping window
    printf("Donner les dimensions de la fenetre: \n");
    printf("xmin : ");
    scanf("%d",&xmin);
    ymin = xmin;
    printf("xmax : ");
    scanf("%d",&xmax);
    ymax = xmax;

    // intialize the graph
    initgraph(&gd, &gm, NULL);

    // Drawing Window using Lines
    line(xmin, ymin, xmax, ymin);
    line(xmax, ymin, xmax, ymax);
    line(xmax, ymax, xmin, ymax);
    line(xmin, ymax, xmin, ymin);

    // Assume 4 lines to be clipped
    int n;
    printf("Donner le nombre des lignes a tracer: ");
    scanf("%d",&n);
    struct lines mylines[n];

    // Setting the coordinated of  4 lines
    for (int i = 0; i < n; i++) {
			printf("Ligne %d\n", i);
       printf("Point 1 :\n");
       printf("x y :");
       scanf("%d %d", &mylines[i].x1,&mylines[i].y1 );
        printf("\nPoint 2 : \n");
       printf("x y :");
       scanf("%d %d", &mylines[i].x2,&mylines[i].y2 );
       printf("\n");
    }


    // Drwaing Initial Lines without clipping
    for (int i = 0; i < n; i++) {
        line(mylines[i].x1, mylines[i].y1,
             mylines[i].x2, mylines[i].y2);
        delay(1000);
    }

    // Drwaing clipped Line
    for (int i = 0; i < n; i++) {
        // Calling clip() which in term clip the line as per window and draw it
        clip(mylines[i]);
        delay(1000);
    }
    delay(4000);
    getch();
    // For Closing the graph.
    closegraph();

}