[maemo-developers] What is the difference between GtkImage, GdkImage, GdkPixmap and GdkBitmap?

[From: Marius Gedminas]

On Fri, Jan 25, 2008 at 05:36:43PM +0800, LIU Chun Hung wrote:
> I don't know the difference between these types(GtkImage, GdkImage,
> GdkPixmap and GdkBitmap) although I have read the GTK and GDK API
> Reference Manual.

Disclaimer: IANAEGD (I Am Not An Experienced Gtk+ Developer).

GtkImage is a widget that you can stick into a window to display image
data (stored in a GdkImage).

GtkPixmap is a widget that you can stick into a window to display image
data (stored in a GdkPixmap).

The difference between an image and a pixmap is that the image is stored
on the client and transfers pixel data to the X server on every redraw
request, while a pixmap is stored on the X server.  Usually this is more
efficient, but if you plan to modify the image, you cannot use pixmaps.

A GdkBitmap is a *bit* map: it's a 1-bit per pixel image, usually used
for things like transparency maps.

> Suppose I want to create a new RGB bitmap with 3 x 3 in size and I want to
> set all pixel values to be 0. After clicking a button, all pixel values
> will change to 255. Which one of the above types should I use? Should
> GdkImage be used as I can see there are functions to change the pixel
> values (gdk_image_put_pixel) in this type, but not in other types.

You would use a GdkImage to manipulate the pixels, and a GtkImage to
display it.

Marius Gedminas
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