Re: [gtkmm] Please help with displaying images

[Murray Cumming <murrayc usa net>]

You do know about Gtk::Image, right?

On Wed, 2003-07-02 at 20:02, Ben Stephens wrote:
> Hi,
>  
> I am having a lot of trouble trying to figure out quite how to create
> a widget for displaying an image. Basically I have got a character
> array, representing an 8 bit image and I want to draw it straight to
> the screen with minimal copying. I think I need to get a Drawable
> object for my widget, but I can't figure out how to do that, and so I
> get compiler errors. I would really appreciate it if someone could:
>  
> a: Tell me how to fix my code (I hope it's fairly self-explanatory
> where the error is, right at the bottom of the source file)
> b: Direct me to an example which specifically uses the draw_gray_image
> or draw_indexed_image functions to achieve the same effect.
>  
> Also, I discovered the pixmap class. Can I use that achieve the same
> effect using this class? (I want it to take the buffer as it's own,
> rather than make a copy, and I also want to draw on the image). I
> would still be curious to know how to fix the code though.
>  
> Thanks for any help.
>  
> Ben Stephens
>  
> -----------------------------------------------------------------------------------------------------------------
>  
> Header file:
>  
> class DisplayWidget : public Gtk::DrawingArea
> {
>  public:
>   SlamGUIDisplay();
>   ~SlamGUIDisplay();
>  
>  protected:
>   // The redraw event
>   virtual bool on_expose_event(GdkEventExpose *event);
>   
>   virtual void on_realize();
>   
>   // Area to store image data
>   char m_Image[500000];
>   
>   // Graphics context
>   Glib::RefPtr<Gdk::GC> gc;
> };
>  
> ------------------------------------------
> Source file:
>  
> #include "slamguidisplay.h"
>  
> SlamGUIDisplay::SlamGUIDisplay()
> {
>  int n;
>  
>  // Create an image (temporary code)
>  for (n = 0; n < 320 * 240; n++)
>   m_Image[n] = n % 320;
> }
>  
> SlamGUIDisplay::~SlamGUIDisplay()
> {
>  
> }
>  
> // Called when the window is created. Only now can you get a valid GC
> for the window
> // This is called only once on startup
> void SlamGUIDisplay::on_realize()
> {
>  // Must call base version
>  Gtk::DrawingArea::on_realize();
>  
>  // Get a GC (Graphics Context)
>  Glib::RefPtr<Gdk::Window> window = get_window();
>  gc = Gdk::GC::create(window);
> }
>  
> // Expose or paint event - called if part or all of the window needs
> updating
> bool SlamGUIDisplay::on_expose_event(GdkEventExpose *event)
> {
>  // ** THIS WILL CAUSE AN ERROR (obviously) BECAUSE I CAN'T GET A
> DRAWABLE OBJECT **
>  Gdk::Drawable::draw_gray_image(gc, 0, 0, 320, 240,
> GDK_RGB_DITHER_NORMAL, (guchar*)m_Image, 320);
> }
-- 
Murray Cumming
murray usa net
www.murrayc.com