[cairo] Saving Transparent Image

Niebruegge, William G william.g.niebruegge at boeing.com
Fri Aug 17 07:19:15 PDT 2007

I have a GTK window using Cairo to create a transparent window (mostly
borrowed code, thank you internet).  I would like to be able to save the
contents of this window into a png (or whatever format works).  I can't
get the image to save with the transparency effect however.  For
example, in this case, instead of getting a yellow tinted image with the
desktop in the background, I just get an opaque yellow image.  I've
tried using:
*	GdkPixbuf
	GdkScreen* screen = gtk_widget_get_screen(widget);
	GdkColormap* colormap = gdk_screen_get_rgba_colormap(screen);
	GdkPixbuf* pb = gdk_pixbuf_get_from_drawable(NULL,
widget->window, colormap, 0, 0, 0, 0, 200, 125);
	gdk_pixbuf_save(pb, "test.png", "png", NULL, NULL);

*	cairo_surface
	cairo_surface_t* cs =
cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 200, 125);
	cairo_set_source_surface(cr, cs, 0.0, 0.0);
	cairo_surface_t* cs2 = cairo_get_target(cr);
	cairo_surface_write_to_png(cs2, "cairo_test.png");

Any ideas on how I can do this?

 <<CairoWindow.cpp>>  <<snapshot3.png>> 


william.g.niebruegge at boeing.com

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