Add overview docs

docs/source/index.rst

@@ -21,6 +21,7 @@ Table of Contents
 .. toctree ::
 
     installing
+    overview
     api
     contributing
     changelog

docs/source/overview.rst

@@ -0,0 +1,53 @@
+Overview
+--------
+
+imagipy is an image processing library. It currently has tools for dealing with
+colors.
+
+Colors
+~~~~~~
+
+Colors are created with the :py:class:`.Color` class:
+
+  >>> import imagipy
+  >>> purple = imagipy.Color(255, 0, 255)
+  >>> purple
+  <Color (255, 0, 255)>
+
+You can also create colors from hex strings:
+
+  >>> orange = imagipy.Color.from_hex("#E67E22")
+  >>> orange
+  <Color (230, 126, 34)>
+
+imagipy comes with some pre-set colors:
+
+  >>> imagipy.Color.YELLOW
+  <Color (241, 196, 15)>
+  >>> imagipy.Color.GRAY
+  <Color (204, 204, 204)>
+  >>> imagipy.Color.BROWN
+  <Color (124, 63, 0)>
+
+You can get a random color, or mutate an existing color to get a slight variant
+on it:
+
+  >>> imagipy.Color.random()
+  <Color (45, 217, 230)>
+  >>> imagipy.Color.random()
+  <Color (249, 244, 177)>
+  >>> imagipy.Color.random()
+  <Color (112, 178, 218)>
+  >>> orange.mutate()
+  <Color (229, 131, 43)>
+  >>> orange.mutate()
+  <Color (216, 127, 28)>
+  >>> orange.mutate()
+  <Color (235, 127, 29)>
+
+Colors can be converted to RGB or hex:
+
+  >>> orange.rgb()
+  (230, 126, 34)
+  >>> orange.hex()
+  '#E67E22'