2.1.3 Drawing in memory

The last way of MathGL using is the drawing in memory. Class mglGraphZB allows one to create a bitmap picture in memory. Further this picture can be displayed in window by some window libraries (like wxWidgets, FLTK, Windows GDI and so on). For example, the code for drawing in wxWidget library looks like:

    void MyForm::OnPaint(wxPaintEvent& event)
    {
        int w,h,x,y;
        GetClientSize(&w,&h);   // size of the picture
        mglGraphZB gr(w,h);

        gr.Alpha(true);         // draws something using MathGL
        gr.Light(true);         gr.Light(0,mglPoint(1,0,-1));
        sample(&gr,NULL);

        wxImage img(w,h,gr.GetBits(),true);
        ToolBar->GetSize(&x,&y);    // gets a height of the toolbar if any
        wxPaintDC dc(this);         // and draws it
        dc.DrawBitmap(wxBitmap(img),0,y);
    }

The drawing in other libraries is most the same.

For example, FLTK code will look like

    void Fl_MyWidget::draw()
    {
        mglGraphZB gr(w(),h());
        gr.Alpha(true);         // draws something using MathGL
        gr.Light(true);         gr.Light(0,mglPoint(1,0,-1));
        sample(&gr,NULL);
        fl_draw_image(gr.GetBits(), x(), y(), gr.GetWidth(), gr.GetHeight(), 3);
    }

Qt code will look like

    void MyWidget::paintEvent(QPaintEvent *)
    {
        mglGraphZB gr(w(),h());
        gr.Alpha(true);         // draws something using MathGL
        gr.Light(true);         gr.Light(0,mglPoint(1,0,-1));
        sample(&gr,NULL);

        // Qt don't support RGB format as is. So, let convert it to BGRN.
        const uchar *bb = gr.GetBits();
        register long i, w=gr.GetWidth(), h=gr.GetHeight();
        *buf = new uchar[4*w*h];
        for(i=0;i<w*h;i++)
        {
            (*buf)[4*i]   = bb[3*i+2];
            (*buf)[4*i+1] = bb[3*i+1];
            (*buf)[4*i+2] = bb[3*i];
            (*buf)[4*i+3] = 255;
        }
        QPixmap pic = QPixmap::fromImage(QImage(*buf, w, h, QImage::Format_RGB32));

        QPainter paint;
        paint.begin(this);  paint.drawPixmap(0,0,pic);  paint.end();
        delete []buf;
    }