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

It looks like your problem is not here, as I have no problem with the following code. You should check your GL init and display setup.

Have you a glEnable(GL_TEXTURE_2D) somewhere ?

Also note glTexCoord2f must be before glVertex2f.

#include 
#include 
#include 

GLuint texture[1] ;

void LoadGLTextures( const char * name )
{
    QImage img;
    if( ! img.load( name ) )
    {
        std::cerr << "error loading " << name << std::endl ;
        exit( 1 );
    }

    QImage GL_formatted_image;
    GL_formatted_image = QGLWidget::convertToGLFormat(img);
    if( GL_formatted_image.isNull() )
    {
        std::cerr << "error GL_formatted_image" << std::endl ;
        exit( 1 );
    }

    glGenTextures(1, texture);
    glBindTexture(GL_TEXTURE_2D, texture[0]);
    glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA,
            GL_formatted_image.width(), GL_formatted_image.height(),
            0, GL_RGBA, GL_UNSIGNED_BYTE, GL_formatted_image.bits() );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); 
}

void resize(int Width, int Height)
{
    glViewport( 0 , 0 , Width , Height );
}

void draw()
{
    glClearColor( 0.0f, 0.0f, 0.0f, 0.0f);
    glClear( GL_COLOR_BUFFER_BIT );

    gluOrtho2D( -1 , 1 , -1 , 1 );

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

    glShadeModel( GL_FLAT );

    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, texture[0]);

    glBegin(GL_TRIANGLES);
    glTexCoord2f( 1.0f, 0.0f);
    glVertex2f( 1.0f, 0.0f);
    glTexCoord2f( 0.0f, 1.0f);
    glVertex2f( 0.0f, 1.0f);
    glTexCoord2f( 0.0f, 0.0f);
    glVertex2f( 0.0f, 0.0f);
    glEnd();

    glutSwapBuffers();
}

int main(int argc, char **argv) 
{  
    glutInit(&argc, argv);  
    glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA );  
    glutInitWindowSize(640, 480);

    glutCreateWindow("Texture"); 

    LoadGLTextures( "star.png" );

    glutDisplayFunc( & draw );  
    glutReshapeFunc( & resize );
    glutMainLoop();  

    return 1;
}