altering transparency in a GtkImage

[Gravis <gtk-app-devel-list adaptivetime com>]

I thought my last email was a bit confusing so I've rewritten it to be
cleared.

I've been working with GtkImages with GdkPixmaps for a while and am
quite privy to their use and altering them.

The one thing I cant do is update the GdkBitmap transparency mask.
alterations before making the GtkImage work great but afterward, no part
of the mask can be altered. My failed attempt have been to alter the
unsigned gchar array that is used to create the mask but I've found that
ineffective... to the point where I free the memory for the array and it
makes no impact on the program.

here's my widget structure:

+window
|-+event
  |-+fixed
    |-GtkImage (no mask)
    |-GtkImage (has GdkBitmap mask) <-- cant update transparency mask


So... how do I alter the transparency mask in a GtkImage after it has 
been created? Does anyone have experience with this? Are there any
examples anywhere?
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In case you are wondering what I can and can't do (so you don't try
answering the wrong question) here you go:
      * I can specify which parts of the GtkImage are to be transparent
        and which to be opaque by using a GdkBitmap (it's created from a
        unsigned char array) before it is created
      * I can alter and update the pixmap for both GtkImages and they
        update on the screen
      * I can draw on the opaque part of the GtkImage on top of the
        other and it shows up fine
      * I can't change which parts of the GtkImage are to be transparent
        and which to be opaque after it is created
______________________________________________________________________

Thanks,
Gravis