6.2节pixel format with necessary capabilities not found

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本文介绍如何使用OpenGL进行颜色映射初始化，并通过旋转角度绘制两条对角线，形成一个X形图案。

#include <GL/glut.h>
#include<gl/gl.h>
#include <stdlib.h>
#include<iostream>
#include <windows.h>

#define RAMPSIZE 16
#define RAMP1START 32
#define RAMP2START 48

static float rotAngle = 0.;

/*  Initialize antialiasing for color-index mode,
 *  including loading a green color ramp starting
 *  at RAMP1START, and a blue color ramp starting
 *  at RAMP2START. The ramps must be a multiple of 16.
 */
void init(void)
{
   int i;
   for (i = 0; i < RAMPSIZE; i++) {
      GLfloat shade;
      shade = (GLfloat) i/(GLfloat) RAMPSIZE;
      glutSetColor(RAMP1START+(GLint)i, 0., shade, 0.);
      glutSetColor(RAMP2START+(GLint)i, 0., 0., shade);
   }
   glEnable (GL_LINE_SMOOTH);
   glHint (GL_LINE_SMOOTH_HINT, GL_DONT_CARE);
   glLineWidth (1.5);

   glClearIndex ((GLfloat) RAMP1START);
}
/*  Draw 2 diagonal lines to form an X */
void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT);

   glIndexi(RAMP1START);
   glPushMatrix();
   glRotatef(-rotAngle, 0.0, 0.0, 0.1);
   glBegin (GL_LINES);
      glVertex2f (-0.5, 0.5);
      glVertex2f (0.5, -0.5);
   glEnd ();
   glPopMatrix();

   glIndexi(RAMP2START);
   glPushMatrix();
   glRotatef(rotAngle, 0.0, 0.0, 0.1);
   glBegin (GL_LINES);
      glVertex2f (0.5, 0.5);
      glVertex2f (-0.5, -0.5);
   glEnd ();
   glPopMatrix();

   glFlush();
}


void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   if (w <= h) 
      gluOrtho2D (-1.0, 1.0, 
         -1.0*(GLfloat)h/(GLfloat)w, 1.0*(GLfloat)h/(GLfloat)w);
   else 
      gluOrtho2D (-1.0*(GLfloat)w/(GLfloat)h, 
         1.0*(GLfloat)w/(GLfloat)h, -1.0, 1.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}
void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 'r':
      case 'R':
         rotAngle += 20.;
         if (rotAngle >= 360.) rotAngle = 0.;
         glutPostRedisplay();   
         break;
      case 27:  /*  Escape Key */
         exit(0);
         break;
      default:
         break;
    }
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_INDEX);
   glutInitWindowPosition(200,200);
   glutInitWindowSize (200, 200);
   glutCreateWindow (argv[0]);
   init();
   glutReshapeFunc (reshape);
   glutKeyboardFunc (keyboard);
   glutDisplayFunc (display);
   glutMainLoop();
   return 0;
}

解释说明：就是计算机不支持index mode，而且没有办法解决。

详细的内容可以参考：http://www.macusenet.com/archive/index-t-21056.html

In article <425c127d_1[at]news3.es.net>,
Andy Nelson <andy[at]thermo.lanl.gov> wrote:

> 1) The above experiment appears to imply that
> the library or hardware does not support color index
> mode in opengl/glut for some reason. Is this correct?

color index mode is not supported.

> 2) Does anyone have any suggestions about whether I'm
> simply doing something wrong (and how to fix it), or
> what what options I have at this point?
>
> Converting the code to RGB mode rather than color
> index mode, would seem to be one option (already somewhere
> in the back of my mind for some years) but will be
> a very major undertaking. Short of that I'm looking
> for some other options.

Why would it be hard? Just do a search and replace to change all calls
that take a color table index to your own code. In your code, use the
index into an array of r,g,b,a quads that you pass to OpenGL.

> 3) Does anyone know the universe in which the word
> `support' means what it did to Chris, my ever so helpful
> support call staffer, this morning? I would like
> to send him a pointer about how to get back there. :/

The library is there. It works. Apple won't help you with it for free.

--
David Phillip Oster