How to save OpenGL images to the BMP file?

I wrote the following code a couple of years ago, having learned and forgotten plenty since then. :embarrassed:

I used it to create bitmaps of spheres with different material properties, which would then be inserted into a listView - it was a materials editor.

HBITMAP makeBmp(material_t materialToUse)
{
    HDC memDC, screenDC;
    HBITMAP result, oldBmp;
    BITMAPINFO bitmapInfo;
    char *bitmapBits;
    RECT myRect;
    HBRUSH myBrush;

    bitmapInfo.bmiHeader.biBitCount = 24;
    bitmapInfo.bmiHeader.biWidth = tileSize;
    bitmapInfo.bmiHeader.biHeight = tileSize;
    bitmapInfo.bmiHeader.biCompression = BI_RGB;
    bitmapInfo.bmiHeader.biPlanes = 1;
    bitmapInfo.bmiHeader.biSize = sizeof(bitmapInfo.bmiHeader);
    bitmapInfo.bmiHeader.biClrImportant = 0;
    bitmapInfo.bmiHeader.biClrUsed = 0;

    screenDC = GetDC(NULL);
    memDC = CreateCompatibleDC(screenDC);

    result = CreateDIBSection(memDC, &bitmapInfo, DIB_RGB_COLORS, (void**)&bitmapBits, 0, 0);

    oldBmp = (HBITMAP)SelectObject(memDC, result);
    myRect.left=0;
    myRect.top=0;
    myRect.right=bitmapInfo.bmiHeader.biWidth;
    myRect.bottom=bitmapInfo.bmiHeader.biHeight;
    //myBrush = CreateSolidBrush(RGB(r,g,b));
    //FillRect(memDC, &myRect, myBrush);
    //DeleteObject(myBrush);

    HGLRC tmpRC;
    tmpRC = EnableOpenGL(memDC);
        glViewport(0, 0, bitmapInfo.bmiHeader.biWidth, bitmapInfo.bmiHeader.biHeight);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        float aspectRatio = (float)bitmapInfo.bmiHeader.biWidth / bitmapInfo.bmiHeader.biHeight;
//        glFrustum(-aspectRatio, -aspectRatio, -1.0, 1.0, 2.0,100.0);
        gldPerspective (40, -aspectRatio, 1, 10.0);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glEnable(GL_LIGHT0);
        glEnable(GL_NORMALIZE);

        glEnable(GL_LIGHTING);

        const GLfloat light_ambient[]  = { 0.3f, 0.3f, 0.3f, 1.0f };
        const GLfloat light_diffuse[]  = { 0.5f, 0.5f, 0.5f, 1.0f };
        const GLfloat light_specular[] = { 0.8f, 0.8f, 0.8f, 1.0f };
        const GLfloat light_position[] = { -3.0f, -4.0f, 5.0f, 0.0f };
        glLightfv(GL_LIGHT0, GL_AMBIENT,  light_ambient);
        glLightfv(GL_LIGHT0, GL_DIFFUSE,  light_diffuse);
        glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
        glLightfv(GL_LIGHT0, GL_POSITION, light_position);

        const GLfloat mat_ambient[]    = { 0.5f, 0.5f, 0.5f, 1.0f };
        const GLfloat mat_diffuse[]    = { 0.8f, 0.8f, 0.8f, 1.0f };
        const GLfloat mat_specular[]   = { 0.9f, 0.9f, 0.9f, 1.0f };
        const GLfloat high_shininess[] = { materialToUse.shininess};
        glMaterialfv(GL_FRONT, GL_AMBIENT,   mat_ambient);
        glMaterialfv(GL_FRONT, GL_DIFFUSE,   mat_diffuse);
        glMaterialfv(GL_FRONT, GL_SPECULAR,  mat_specular);
        glMaterialfv(GL_FRONT, GL_SHININESS, high_shininess);

        glEnable(GL_COLOR_MATERIAL);
        glClearColor(1,1,1,1.0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        GLfloat rr,gg,bb;
        rr=(int)materialToUse.r/255.0;
        gg=(int)materialToUse.g/255.0;
        bb=(int)materialToUse.b/255.0;

        glTranslated(0,0,-3);
        glRotated(-90,1,0,0);

        glColor3d(rr,gg,bb);

        myGlutBall(1, 32,32);

        SwapBuffers(memDC);

    wglMakeCurrent( NULL, NULL );
    wglDeleteContext( tmpRC );

    SelectObject(memDC, oldBmp);
    DeleteDC(memDC);

    return result;
}

Basically, I think you can cull all code between EnableOpenGL and SwapBuffer, replacing it with the code you have. Note: that this code does not make use of anything other than 'raw' openGL - no use of glut or glaux or any other frameworks/libraries. I've no idea what you would need to modify/write to achieve the same with one.

If you combine this code with some that will write a HBITMAP to a .BMP file, you should have what you need.

You should also continue to improve and hone your problem-solving skills. Namely, break-down a problem into manageable components, before solving each of them - either by yourself with some help from google & forums, or by simply searching for code you can copy and paste. I would generally ignore a request similar to yours - however, I'm in a good mood, you asked if we could help (rather than telling us to help, as many do), also, you didn't say "it's urgent".

I debated whether or not to answer, lest it encourage others to ask questions without trying to solve the problem first. I figured, you'll hopefully read my advice regarding solving a problem on your own, as would they. Besides, generally speaking, someone that wants to learn should be rewarded, I think!