[babl/wip/pippin/inverted-cmyk: 6/11] docs: update with information about CMYK

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 5d68fe24fc4087145b328b13bd19e9f5b50256cc
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Nov 12 23:36:51 2018 +0100

    docs: update with information about CMYK

 docs/index-static.html.in | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
---
diff --git a/docs/index-static.html.in b/docs/index-static.html.in
index 16ca612..033b9f6 100644
--- a/docs/index-static.html.in
+++ b/docs/index-static.html.in
@@ -355,6 +355,22 @@ lab_buffer  = malloc (pixel_count * 3 * sizeof (float));
     </div>
         -->
 
+  <a name='cmyk'></a>
+  <h2>CMYK</h2>
+
+  <p>CMYK handling is done using babl-spaces created with ICC profiles containing CMYK profiles</p>
+  <p>CMYK in babl has only two component encodings, the components as described
+in ICC and the corresponding premultiplied alpha version of them. cmykA and
+camayakaA are the core encodings used, with u8 u16 half or float. The encoded
+in pixel data is inverted to make the components usable with additive math in
+GEGL.</p>
+<p>lower case is used since it then uniquely distinguishes y from the already
+existing componeny Y</p>.
+  <p>If compiled without lcms2, babl will still deal with CMYK formats but will fall back to an internal 
sRGB related conversion.</p>
+<p>RGB encodings can also be created from the CMYK space, the RGB encodings behaves as sRGB</p>
+<p>When converting between CMYK spaces currently nothing is done, better than
+all wrong, lcms2 can do K preserving conversions which should be used - but additional memory management of 
on-demand created and cached conversions will be needed.</p>
+
   <a name='premultiplied-alpha'></a>
   <h2>Pre-multiplied alpha</h2>