给出一个OpenGL扩展应用的实例

// opngl_kuozhan.cpp : Defines the entry point for the console application.
//其中，画红线的部分是要注意的。

#include "stdafx.h"
#include <iostream>

#include <windows.h>

#include <GL/glew.h>//顺序要正确。

#include <GL/glut.h>

using namespace std ;

void init(void)

{

         glClearColor(1.0, 1.0, 0.0, 0.0) ;

         glBlendFunc(GL_ONE, GL_ONE) ;

         glEnable(GL_BLEND) ;

}

void display(void)

{

         glClear(GL_COLOR_BUFFER_BIT) ;

         glColor3f(0.0, 0.0, 1.0) ;

         glRectf(-0.5, -0.5, 0.5, 0.5) ;

         glFlush() ;

}

void reshape(int w, int h)

{

         glViewport(0, 0, (GLsizei)w, (GLsizei)h) ;

         glMatrixMode(GL_PROJECTION) ;

         glLoadIdentity() ;

         if(w<=h)

                   glOrtho(-1.5, 1.5, -1.5*(GLfloat)h/(GLfloat)w,

                   1.5*(GLfloat)h/(GLfloat)w, -10.0, 10.0) ;

         else

                   glOrtho(-1.5*(GLfloat)w/(GLfloat)h,

                   1.5*(GLfloat)w/(GLfloat)h, -1.5, 1.5, -10.0, 10.0) ;

         glMatrixMode(GL_MODELVIEW) ;

         glLoadIdentity() ;

}

void keyboard(unsigned char key, int x, int y)

{

         switch(key)

         {

         case 'a':

         case 'A':

                   //Note: glBlendEquation is a subset of GL_ARB_imaging, please call glGetString

                   //first to confirm whether your video card support this extension.

                   glBlendEquation(GL_FUNC_ADD) ;

                   break ;

         case 's':

         case 'S':

                   glBlendEquation(GL_FUNC_SUBTRACT) ;

                   break ;

         case 'r':

         case 'R':

                   glBlendEquation(GL_FUNC_REVERSE_SUBTRACT) ;

         case 'm':

         case 'M':

                   glBlendEquation(GL_MIN) ;

                   break ;

         case 'x':

         case 'X':

                   glBlendEquation(GL_MAX) ;

                   break ;

         case 27:

                   exit(0) ;

                   break ;

         }

         glutPostRedisplay() ;

}

int main(int argc, char* argv[])
{
 glutInit(&argc, argv) ;
 
 glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB) ;
 
 glutInitWindowSize(200, 200) ;
 
 glutCreateWindow("Blend") ;
 
 
 
 GLenum err = glewInit();//初始化glew库
 
 if (GLEW_OK != err)
  
 {
  
  MessageBoxA(NULL, "error", "My Window", 1) ;
  
 }
 
 //if the return value contains "GL_ARB_imaging " then you can use glBlendEquation
 
 const GLubyte *str = glGetString(GL_EXTENSIONS) ;
 
 cout << str << endl ;//输出硬件所支持的所有扩展本例中主要是"GL_ARB_imaging "
 
 init() ;
 
 glutReshapeFunc(reshape) ;
 
 glutKeyboardFunc(keyboard) ;
 
 glutDisplayFunc(display) ;
 
 glutMainLoop() ;
 
 return 0 ;
 

}
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