Hi I have the same problem. In my case, I am drawing the result on a bitmap using PFD_DRAW_TO_BITMAP. The drawing works fine but I cannot do blending because wglGetProcAddress returns always NULL. The error message says it cannot find the procedure but it works if I draw the result in a window. What is the problem? Why it works in a code but not does not in another code?
// DrawOnBitmap.cpp : Defines the entry point for the application.
//
#include <windows.h> // Header File For Windows
#include <gl\gl.h> // Header File For The OpenGL32 Library
#include <gl\glu.h> // Header File For The GLu32 Library
#include <gl\glaux.h> // Header File For The Glaux Library
#include “MIPLib.h”
HDC hDC=NULL; // Private GDI Device Context
HGLRC hRC=NULL; // Permanent Rendering Context
HINSTANCE hInstance; // Holds The Instance Of The Application
bool keys[256]; // Array Used For The Keyboard Routine
bool active=TRUE; // Window Active Flag Set To TRUE By Default
bool fullscreen=TRUE; // Fullscreen Flag Set To Fullscreen Mode By Default
int WINAPI WinMain( HINSTANCE hInstance, // Instance
HINSTANCE hPrevInstance, // Previous Instance
LPSTR lpCmdLine, // Command Line Parameters
int nCmdShow) // Window Show State
{
CreateAWindow();
int width=512;
int height=512;
int bits=24;
BITMAPINFO g_BitmapInfo;
HDC hDc = GetDC( NULL );
memset( &g_BitmapInfo, 0, sizeof(BITMAPINFO) );
g_BitmapInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
g_BitmapInfo.bmiHeader.biWidth = width;
g_BitmapInfo.bmiHeader.biHeight = height;
g_BitmapInfo.bmiHeader.biPlanes = 1;
g_BitmapInfo.bmiHeader.biBitCount = 24;
g_BitmapInfo.bmiHeader.biCompression = BI_RGB;
BYTE **g_pBitmapBits;
HBITMAP g_hBitmapImage = CreateDIBSection( hDc, &g_BitmapInfo, DIB_RGB_COLORS,
(void **)(&g_pBitmapBits), NULL, 0 );
ReleaseDC( NULL, hDc );
PIXELFORMATDESCRIPTOR pfd ;
memset(&pfd,0,sizeof(PIXELFORMATDESCRIPTOR)) ;
pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR) ;
pfd.nVersion = 1 ;
pfd.dwFlags = PFD_DRAW_TO_BITMAP | // replaces PFD_DRAW_TO_WINDOW
PFD_SUPPORT_OPENGL |
PFD_SUPPORT_GDI|PFD_STEREO_DONTCARE ;
pfd.iPixelType = PFD_TYPE_RGBA ;
pfd.cColorBits = 24 ;
pfd.cAlphaBits = 0;
pfd.cDepthBits = 8;
pfd.iLayerType = PFD_MAIN_PLANE ;
// create memory dc
HDC dcMem=CreateCompatibleDC(NULL);
if(dcMem==NULL)
{
MessageBox(NULL,"Fail to create memory DC!","ERROR",MB_OK|MB_ICONEXCLAMATION);
return -1;; // return -1;
}
// select bitmap to the memory dc
SelectObject(dcMem,g_hBitmapImage);
GLuint pxFormat; // Holds The Results After Searching For A Match
if (!(pxFormat=ChoosePixelFormat(dcMem,&pfd))) // Did Windows Find A Matching Pixel Format?
{
MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
DeleteDC(dcMem);
DeleteObject(g_hBitmapImage);
return -1;; // return -1;
}
if(!SetPixelFormat(dcMem,pxFormat,&pfd)) // Are We Able To Set The Pixel Format?
{
MessageBox(NULL,"Can't set the given PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
DeleteDC(dcMem);
DeleteObject(g_hBitmapImage);
return -1;; // return -1;
}
if (!(hRC=wglCreateContext(dcMem))) // Are We Able To Get A Rendering Context?
{
MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
DeleteDC(dcMem);
DeleteObject(g_hBitmapImage);
return -1;; // return -1;
}
if(!wglMakeCurrent(dcMem,hRC)) // Try To Activate The Rendering Context
{
DeleteDC(dcMem);
DeleteObject(g_hBitmapImage);
wglDeleteContext(hRC);
MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return -1;; // return -1;
}
// set view port
glViewport(0,0,width,height); // Reset The Current Viewport
// set the view port
glMatrixMode(GL_PROJECTION); // Select The Projection Matrix
glLoadIdentity(); // Reset The Projection Matrix
glFrustum(-1.0,1.0,-1.0,1.0,1.0,5.0);
glMatrixMode(GL_MODELVIEW); // Select The Modelview Matrix
glLoadIdentity();
////////////
// init gl
glShadeModel(GL_SMOOTH); // Enable Smooth Shading
glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black Background
glClearDepth(1.0f); // Depth Buffer Setup
glEnable(GL_DEPTH_TEST); // Enables Depth Testing
glDepthFunc(GL_LEQUAL); // The Type Of Depth Testing To Do
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really Nice Perspective Calculations
////////////////////
// draw a triangle
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer
glLoadIdentity(); // Reset The Current Modelview Matrix
glTranslatef(0.0f,0.0f,-2.0f); // Move Left 1.5 Units And Into The Screen 6.0
glBegin(GL_TRIANGLES); // Drawing Using Triangles
glVertex3f( 0.0f, 1.0f, 0.0f); // Top
glVertex3f(-1.0f,-1.0f, 0.0f); // Bottom Left
glVertex3f( 1.0f,-1.0f, 0.0f); // Bottom Right
glEnd();
///////////////////////////
// save the result to a file
CRGBByteImage img(width,height);
glReadPixels(0,0,width,height,GL_RGB,GL_UNSIGNED_BYTE,img.GetPtrOfData());
img.FlipV();
img.SaveAsBmp("screen.bmp");
/////////// this line always returns NULL !!! Why????
PFNGLBLENDCOLORPROC glBlendColor=(PFNGLBLENDCOLORPROC)wglGetProcAddress("glBlendColor");
///////////////////////////
// close
MessageBox(NULL,"Done!","OK",MB_OK);
DeleteDC(dcMem);
DeleteObject(g_hBitmapImage);
if (hRC) // Do We Have A Rendering Context?
{
if (!wglMakeCurrent(NULL,NULL)) // Are We Able To Release The DC And RC Contexts?
{
MessageBox(NULL,"Release Of DC And RC Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}
if (!wglDeleteContext(hRC)) // Are We Able To Delete The RC?
{
MessageBox(NULL,"Release Rendering Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}
hRC=NULL; // Set RC To NULL
}
return 1;
}