Re: Transparency

[Russell Shaw <rjshaw iprimus com au>]

Julio Pastrana wrote:
> Hello Russell here are some examples
> 
> http://mail.gnome.org/archives/gtk-app-devel-list/2003-October/msg00067.html
> 
> http://mail.gnome.org/archives/gtk-app-devel-list/2003-October/msg00369.html

Thanks. These examples make transparent as in "clear" masks. I want to draw
a rectangle that scales the RGB components of whatever is behind it.
I could then draw a rectangle on a white background that halves the
red and green components to give a light blue with the covered objects
still visible.

To use gdk_draw_rgb_image, how can i get the pixels from a GdkDrawable
into the rgb_buf array? :

void gdk_draw_rgb_image(GdkDrawable *drawable,
                         GdkGC *gc,
                         gint x,
                         gint y,
                         gint width,
                         gint height,
                         GdkRgbDither dith,
                         guchar *rgb_buf,
                         gint rowstride);