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pixbuf.c - new library functions

The Gtk way of drawing to pixbufs and drawable objects is through the use of Cairo. This is fine if you're working with screen objects or, you want nicely draw vector objects to build UI components. The use of the GdkPixbuf provides a convenient platform for a number of image manipulation operations. There are already some experimental filters in the gnocl core and today I added some extra functionality line and circle drawing plus flood fill. These are all pixel based and not anti-aliased but are lightning fast.

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