line.c

#include <windows.h>
#include <math.h>
#include <GL/glut.h>

#define WIDTH 400
#define HEIGHT 300
#define STEP 13

int buff[WIDTH][HEIGHT];

typedef struct color{
    float r,g,b;
}Color3f;

typedef struct line{
    int x1,y1,x2,y2;
}Line;

int X=0,Y=0, DX=0, DY=0;
int banderaP = 0, leftPressed = 0;

void mouse(int btn, int state, int x, int y){
    if(state == GLUT_DOWN && btn == GLUT_LEFT_BUTTON){
        leftPressed=1;
        banderaP=1;
        X=x;
        Y=HEIGHT-y;
        DX=X;
        DY=Y;
    }else if(state == GLUT_UP && btn == GLUT_LEFT_BUTTON){
        banderaP=0;
        DX=x;
        DY=HEIGHT-y;
        glutPostRedisplay();
    }else{
        leftPressed=0;
    }
}
void mouseMotion(int x, int y){
    DX=x;
    DY=HEIGHT-y;
    glutPostRedisplay();
}

void init(void)
{
   glClearColor(1.0, 1.0, 1.0, 0.0); // color de la ventana, blanco
   glMatrixMode(GL_PROJECTION);      //  proyección de la imagen en la ventana de visualización
   gluOrtho2D(0.0, (double)WIDTH, 0.0, (double)HEIGHT); //  proyección en 2D
   glClear(GL_COLOR_BUFFER_BIT);
   glReadPixels(0,0,WIDTH,HEIGHT,GL_RGB,GL_UNSIGNED_BYTE,buff);
}

void linea(int x1, int y1, int x2, int y2, Color3f color, int modo){
    glColor3f(color.r, color.g, color.b);

    int step;
    if(modo==1){
        step = STEP;
    }else if(modo==0){
        step = 1;
    }

    int i, j, xaux, yaux, dx, dy, p, incX, incY;
    dx = abs(x2-x1);
    dy = abs(y2-y1);

    if(dx>dy){
        if(x1>x2){
            xaux=x1;
            yaux=y1;
            x1=x2;
            y1=y2;
            x2=xaux;
            y2=yaux;
        }
        xaux=x1;
        yaux=y1;

        glBegin(GL_POINTS);
            glVertex2i(xaux, yaux);
        glEnd();

        p = 2.0*dy-dx;

        incY=y2>y1?1:-1;
        i=x1;
        while(i<x2){
            for(j=0;j<step;j++){
                xaux++;
                i++;
                if(p<0){
                    p=p+2*dy;
                }else{
                    yaux+=incY;
                    p = p+2*(dy-dx);
                }
                if(i<x2){
                    glBegin(GL_POINTS);
                        glVertex2i(xaux, yaux);
                    glEnd();
                }
            }
            for(j=0;j<step;j++){
                xaux++;
                i++;
                if(p<0){
                    p=p+2*dy;
                }else{
                    yaux+=incY;
                    p = p+2*(dy-dx);
                }
                if(modo==0&&i<x2){
                    glBegin(GL_POINTS);
                        glVertex2i(xaux, yaux);
                    glEnd();
                }
            }
        }
    }else{
        if(y1>y2){
            xaux=x1;
            yaux=y1;
            x1=x2;
            y1=y2;
            x2=xaux;
            y2=yaux;
        }
        xaux=x1;
        yaux=y1;
        glBegin(GL_POINTS);
            glVertex2i(xaux, yaux);
        glEnd();
        p = 2.0*dx-dy;
        incX=x2>x1?1:-1;
        i=y1;
        while(i<y2){
            for(j=0;j<step;j++){
                yaux++;
                i++;
                if(p<0){
                    p=p+2*dx;
                }else{
                    xaux+=incX;
                    p = p+2*(dx-dy);
                }
                if(i<y2){
                    glBegin(GL_POINTS);
                        glVertex2i(xaux, yaux);
                    glEnd();
                }
            }
            for(j=0;j<step;j++){
                yaux++;
                i++;
                if(p<0){
                    p=p+2*dx;
                }else{
                    xaux+=incX;
                    p = p+2*(dx-dy);
                }
                if(modo==0&&i<y2){
                    glBegin(GL_POINTS);
                        glVertex2i(xaux, yaux);
                    glEnd();
                }
            }
        }
    }
}

void dibujaLinea(void){
    glClear(GL_COLOR_BUFFER_BIT);
    Color3f c;
    c.r=0.0;
    c.g=0.0;
    c.b=1.0;
    glDrawPixels(WIDTH,HEIGHT,GL_RGB,GL_UNSIGNED_BYTE,buff);
    if(leftPressed==1 && (X!=DX || Y!=DY)){
        if(banderaP==1){
            glDrawPixels(WIDTH,HEIGHT,GL_RGB,GL_UNSIGNED_BYTE,buff);
            linea(X,Y,DX,DY,c,1);
        }else{
            glDrawPixels(WIDTH,HEIGHT,GL_RGB,GL_UNSIGNED_BYTE,buff);
            linea(X,Y,DX,DY,c,0);
            glReadPixels(0,0,WIDTH,HEIGHT,GL_RGB,GL_UNSIGNED_BYTE,buff);
            leftPressed=0;
        }
    }
    glFlush();
}
int main(int argc, char** argv)
{
     glutInit(&argc, argv);  //inicialización de GLUT
     glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);  //único búfer de refresco en la ventana de visualización y el modo de color RGB
     glutInitWindowPosition(50, 100); // posición inicial, esq sup izq
     glutInitWindowSize(WIDTH, HEIGHT); // alto y ancho de la ventana en pixeles
     glutCreateWindow("Interactive Bresenham");      // creación de ventana de visualización y título de la misma
     init();
     glutDisplayFunc(dibujaLinea);
     glutMouseFunc(mouse);
     glutMotionFunc(mouseMotion);
     glutMainLoop(); // bucle infinito que comprueba entrada de disp
     return EXIT_SUCCESS;
}