Graphics-and-Multimedia/bresenhamsample.cpp at main · imsreyas7/Graphics-and-Multimedia · GitHub

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// Q: To plot points that make up the line with endpoints (x0,y0) and (xn,yn) using Bresenham's line drawing algorithm.

    // Case 1: +ve slope Left to Right line
    // Case 2: +ve slope Right to Left line
    // Case 3: -ve slope Left to Right line
    // Case 4: -ve slope Right to Left line

    // Each case has two subdivisions
    //     (i) |m|<= 1
    //     (ii) |m|>1
    // Note that all four cases of line drawing must be given as test cases.

#include<bits/stdc++.h>
#include<GL/glut.h>

using namespace std;
using ld = long double;

const int WINDOW_WIDTH = 850;
const int WINDOW_HEIGHT = 700;

void myInit();
void myDisplay();

void printLines();
void printBresenhamLine(ld x1, ld y1, ld x2, ld y2);

const ld PADDING = 250;
const ld STEP = 1;
const ld SCALE = 5;

int main(int argc,char* argv[]) {
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
    glutInitWindowSize(WINDOW_WIDTH,WINDOW_HEIGHT);
    glutCreateWindow("Breseham's Line Drawing Algorithm");
    glutDisplayFunc(myDisplay);
    myInit();
    glutMainLoop();
    return 1;
}

void myInit() {
    glClearColor(1.0,1.0,1.0,0.0);
    glColor3f(0.0f,0.0f,0.0f);
    glPointSize(2.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0,640.0,0.0,480.0);
}

void myDisplay() {
    glClear(GL_COLOR_BUFFER_BIT);

    printLines();

    glFlush();
}


void printLines() {
    glBegin(GL_POINTS);

    // Case 1: +ve slope Left to Right line
    glColor3f(1.0f,0.0f,0.0f);
    // | m | > 1
    printBresenhamLine((ld)3,(ld)2, (ld)15,(ld)10);
    // | m | < 1
    printBresenhamLine((ld)2,(ld)3, (ld)10,(ld)15);

    // Case 2: +ve slope Right to Left line
    glColor3f(0.5f,0.5f,0.0f);
    // | m | > 1
    printBresenhamLine((ld)-3,(ld)-2, (ld)-15,(ld)-10);
    // | m | < 1
    printBresenhamLine((ld)-2,(ld)-3, (ld)-10,(ld)-15);

    //Case 3: -ve slope Left to Right line
    glColor3f(0.0f,1.0f,0.0f);
    // | m | > 1
    printBresenhamLine((ld)3,(ld)-2, (ld)15,(ld)-10);
    // | m | < 1
    printBresenhamLine((ld)2,(ld)-3, (ld)10,(ld)-15);

    //Case 4: -ve slope Right to Left line
    glColor3f(0.0f,0.5f,0.5f);
    // | m | > 1
    printBresenhamLine((ld)-3,(ld)2, (ld)-15,(ld)10);
    // | m | < 1
    printBresenhamLine((ld)-2,(ld)3, (ld)-10,(ld)15);

    glEnd();
}

void printBresenhamLine(ld x1, ld y1, ld x2, ld y2) {
    // m : slope;
    ld pad = PADDING, scale = SCALE;

    x1 = x1*scale + pad;
    x2 = x2*scale + pad;
    y1 = y1*scale + pad;
    y2 = y2*scale + pad;

    ld dx, dy;
    ld x, y, xEnd, p, mirrorLine;
    bool printMirror = false;

    dx = abs(x2-x1);
    dy = abs(y2-y1);

    p = 2*dy - dx;

    if(x1 > x2) swap(x1,x2), swap(y1, y2);

    x = x1;
    y = y1;
    xEnd = x2;

    glVertex2d(x,y);

    if(y1 > y2) {
        mirrorLine = y;
        printMirror = true;
        y2 = y1 + (y1 - y2);
    }

    while(x < xEnd) {
        x ++;

        if(p < 0) {
            p += 2*dy;
        } else {
            y ++;
            p = 2*(dy-dx);
        }

        if(printMirror) glVertex2d(x,mirrorLine - (y-mirrorLine));
        else            glVertex2d(x,y);

    }
}