The lines:
// window_x_, window_y_ … size of (glut-created) window
GLubyte* img_buf = new GLubyte [3 * window_x_ * window_y_];
glReadPixels (0, 0, window_x_, window_y_, GL_RGB, GL_UNSIGNED_BYTE, (GLvoid*) img_buf);
I use Windows 98. Graphic-Card: ATI Rage Mobility. I link against Opengl32, glu32, glut32 - libraries (i think these are the one from SGI).
I had to turn “hardware accelerating” off because otherwise the os crashed periodly when i debugged my opengl-program.
The strang thing is that ‘glReadPixels’ already worked fine. Then i added some features to my program and now glReadPixels does nothing.
please call glGetString(GL_VENDOR), glGetString(GL_RENDERER) and glGetString(GL_VERSION) and post here the results. Because turning hardware acceleration to off may switch your engine to software rendering (and those calls will show that),
now that you added a few lines of code, do you call glPixelStore, glPixelTransfer or glPixelMap ?