Question

我使用QUAD_STRIP显示不同颜色的方块和鼠标功能来捕捉颜色。捕获的颜色应设置为spehre。我可以读取颜色值，但我无法将读取颜色值设置为球体。在鼠标功能中给出时不显示球体。但是在display（）函数中给出时会显示出来。

        #include <stdlib.h>
    #include <GL/gl.h>
    #include <GL/glu.h>
    #include <GL/glut.h>
    #include<windows.h>    
    float height=480,width=500;        
    GLUquadricObj *sphere = NULL;
    GLubyte *img;
    static void Init() {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
        glShadeModel(GL_FLAT);
                    sphere = gluNewQuadric();
        gluQuadricDrawStyle(sphere, GLU_FILL);
        gluQuadricTexture(sphere, GL_TRUE);
        gluQuadricNormals(sphere, GLU_SMOOTH);

        glClearColor(1,1,1,0);

    }

    static void display() {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   //glColor3f(0.0f, 0.0f, 0.0f); // sets color to black.
          glBegin(GL_QUAD_STRIP);
    //1 q
            glColor3f(.5,0.5,1);
            glVertex2f(-1, 0.5 );
            glVertex2f(-1, 0.75 );
            glVertex2f(-0.75, 0.5 );
            glVertex2f(-0.75, 0.75 );
            // 2q
            glColor3f(.25,.5,0);

            glVertex2f(-0.5, 0.5 );
            glVertex2f(-0.5, 0.75 );

            //3q
            glColor3f(0.8,0.8,0.4);

            glVertex2f(-0.25, 0.5 );
            glVertex2f(-0.25, 0.75 );
            // 4th QUAD
            glColor3f(0.7,0.3,0.6);
            glVertex2f(0, 0.5);
            glVertex2f(0, 0.75 );

            // 5th QUAD
            glColor3f(0, 0.7,0.3);

            glVertex2f( 0.25, 0.5);
            glVertex2f(0.25,  0.75 );

    glEnd();

   glBegin(GL_QUAD_STRIP);
    //1 q
            glColor3f(.5,0.5,.5);
            glVertex2f(-1, 0.25 );
            glVertex2f(-1, 0.5 );
            glVertex2f(-0.75, 0.25 );
            glVertex2f(-0.75, 0.5 );
            // 2q
            glColor3f(.5,0.1,0.1);

            glVertex2f(-0.5, 0.25 );
            glVertex2f(-0.5, 0.5 );

            //3q
            glColor3f(0.1,0.1,0.4);

            glVertex2f(-0.25, 0.25 );
            glVertex2f(-0.25, 0.5 );
            // 4th QUAD
            glColor3f(1,1,0.5);
            glVertex2f(0, 0.25);
            glVertex2f(0, 0.5 );

            // 5th QUAD
            glColor3f(0.76, 0.3,0);

            glVertex2f( 0.25, 0.25);
            glVertex2f(0.25,  0.5 );

    glEnd();

    glBegin(GL_QUAD_STRIP);
    //1 q
            glColor3f(.5,0,.5);
            glVertex2f(-1, 0 );
            glVertex2f(-1, 0.25 );
            glVertex2f(-0.75, 0 );
            glVertex2f(-0.75, 0.25 );
            // 2q
            glColor3f(.5,.3,0.3);

            glVertex2f(-0.5, 0 );
            glVertex2f(-0.5, 0.25 );

            //3q
            glColor3f(0.2,0.3,0);

            glVertex2f(-0.25, 0 );
            glVertex2f(-0.25, 0.25 );
            // 4th QUAD
            glColor3f(0,0,0);
            glVertex2f(0, 0);
            glVertex2f(0, 0.25 );

            // 5th QUAD
            glColor3f(1.0, 0,.5);

            glVertex2f( 0.25, 0);
            glVertex2f(0.25,  0.25 );

    glEnd();

    glBegin(GL_QUAD_STRIP);
            glColor3f(1,0.5,0);
            glVertex2f(-1, -0.25 );
            glVertex2f(-1, 0.0 );
            glVertex2f(-0.75, -0.25 );
            glVertex2f(-0.75, 0.0 );

            glColor3f(1.0,1.0,0.0);

            glVertex2f(-0.5, -0.25 );
            glVertex2f(-0.5, 0.0 );


            glColor3f(0.0,0.0,1.0);

            glVertex2f(-0.25, -0.25 );
            glVertex2f(-0.25, 0.0 );
            // 2nd QUAD
            glColor3f(1.0, 0.0, 0.0);
            glVertex2f(-0.25, -0.25 );
            glVertex2f(-0.25, 0.0 );

            glVertex2f( 0, -0.25 );
            glVertex2f(0,  0.0 );

            // 3rd QUAD
            glColor3f(0.0, 1.0, 0.0);

            glVertex2f( 0.25, -0.25 );
            glVertex2f(0.25,  0.0 );

    glEnd();
glutSwapBuffers();

    }
    void moveBall(int key, int x, int y) {
    }
        void mouseMove(int x,int y) {
            y = glutGet( GLUT_WINDOW_HEIGHT ) - y;
            GLubyte pixel[3];
            float r,g,b;
            glReadPixels(x, y, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, pixel);
            r = pixel[0]/255.0;
            g = pixel[1]/255.0;
            b = pixel[2]/255.0;
            printf("red %f",r);
            printf("green %f",g);
            printf("blue %f",b);
            glColor3f(r,g,b);
            glTranslatef(0.75,0.25,0);
            gluSphere(sphere,0.1,20,20);
        }
    int main(int argc, char** argv) {

        glutInit(&argc,argv);
        glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
        glutInitWindowPosition( 10, 10);
        glutInitWindowSize(height,width);
        glutCreateWindow( "ColorBlocks");
        Init();
        glutDisplayFunc(display);
        glutSpecialFunc(moveBall);
        glutMotionFunc(mouseMove);
        glutMainLoop();

    }

Answer 1

你应该做的是将球体的绘图放在显示器中，并使用你在mouseMove中获得的变量来定位它并设置为全局：

float sphereR,sphereG,sphereB;
void display(){
    //everything before the glutSwapBuffers(); call...

    glPushMatrix()
        glColor3f(r,g,b);
        glTranslatef(0.75,0.25,0);
        gluSphere(sphere,0.1,20,20);
    glPopMatrix()
    glutSwapBuffers();
}

void mouseMove(int x,int y) {
    y = glutGet( GLUT_WINDOW_HEIGHT ) - y;
    GLubyte pixel[3];

    glReadPixels(x, y, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, pixel);
    sphereR = pixel[0]/255.0;
    sphereG = pixel[1]/255.0;
    sphereB = pixel[2]/255.0;
    printf("red %f",r);
    printf("green %f",g);
    printf("blue %f",b);

}

在OpenGL中将像素颜色设置为球体

1 个答案: