Using QImage with OpenGL

Question

I\'ve very recently picked up Qt and am using it with OpenGL The thing though is that when moving my SDL code to Qt and changing the texture code to use QImage it stops work

Answer 1

I have similar code that works but uses glTexSubImage2D :

void Widget::paintGL() 
{
    glClear (GL_COLOR_BUFFER_BIT);       
    glDisable(GL_DEPTH_TEST);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();        
    gluOrtho2D(0,win.width(),0,win.height());
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();        
    glEnable(GL_TEXTURE_2D);

    glBindTexture(GL_TEXTURE_2D,texture); 
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0,0 , image.width(), image.height(),  glFormat, glType, image.bits() );       
    glBegin(GL_QUADS);   // in theory triangles are better
    glTexCoord2i(0,0); glVertex2i(0,win.height());
    glTexCoord2i(0,1); glVertex2i(0,0);
    glTexCoord2i(1,1); glVertex2i(win.width(),0);
    glTexCoord2i(1,0); glVertex2i(win.width(),win.height());
    glEnd();             

    glFlush();
}


void Widget::initializeGL() 
{
    glClearColor (0.0,0.0,0.0,1.0);
    glDisable(GL_DEPTH_TEST);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();        
    gluOrtho2D(0,win.width(),0,win.height());
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();        

    glEnable(GL_TEXTURE_2D);
    glGenTextures(3,&texture);
    glBindTexture(GL_TEXTURE_2D,texture);       
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);          
    glBindTexture(GL_TEXTURE_2D,texture);               
    glTexImage2D(GL_TEXTURE_2D, 0, glFormat, image.width(), image.height(), 0, glFormat, glType, NULL );    

    glDisable(GL_TEXTURE_2D);
}

And a few perfomance tweaks in the ctor

void Widget::setDisplayOptions()
{
    glFormat = GL_RGB;  //  QImage RGBA is BGRA
    glType = GL_UNSIGNED_BYTE;

    QGL::setPreferredPaintEngine(QPaintEngine::OpenGL2);

    QGLFormat glFmt;
    glFmt.setSwapInterval(1); // 1= vsync on 
    glFmt.setAlpha(GL_RGBA==glFormat);
    glFmt.setRgba(GL_RGBA==glFormat); 
    glFmt.setDoubleBuffer(true); // default
    glFmt.setOverlay(false);
    glFmt.setSampleBuffers(false);
    QGLFormat::setDefaultFormat(glFmt);

    setAttribute(Qt::WA_OpaquePaintEvent,true);
    setAttribute(Qt::WA_PaintOnScreen,true);        
}