The image files in this folder are in "Silicon Graphics RGB"
format.  They were originally downloaded in other formats
and were converted to .rgb files using the Gimp image
manipulation program.

.rgb is a simple file format.  The images can be loaded
into GL_RGBA format textures using the readrgb.c file
that can be found in this folder.  It was downloaded 
from http://paulbourke.net/dataformats/sgirgb/ 
in June 2021.

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Earth-1024x512.jpg is a resized image from
http://maps.jpl.nasa.gov/ (courtesy NASA/JPL-Caltech)
Image can be freely distributed but should credit
the NASA/JPL-Caltec.

Earth-512x256.jpg is also a Nasa image but was obtained
from Astronomy Picture of the Day,
http://apod.nasa.gov/apod/ap081005.html

brick001.jpg and metal003.gif are from
http://www.grsites.com/archive/textures/
a collection of free background images.

mandelbrot.png is original by David Eck and is 
released by him into the public domain.

I'm not sure where I got marble.jpg, but it was
made available as redistributable.