diff -r da0024f4f068 -r 2e3bc2435d68 measurement.rst
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/measurement.rst	Sat Feb 20 23:13:00 2016 +0200
@@ -0,0 +1,52 @@
+.. -*- coding: utf-8; -*-
+.. include:: HEADER.rst
+
+=============
+ Measurement
+=============
+.. contents::
+
+dpi
+===
+
+Dots per inch.
+
+  http://en.wikipedia.org/wiki/Dots_per_inch
+
+ppi
+===
+
+pixels per inch, pixel density.
+
+====== =========== ===
+ Inch  Resolution  ppi
+====== =========== ===
+  17"   1280x1024   96
+  19"   1280x1024   86
+  19"   1600x1200  105
+  21"   1600x1200   95
+   2"    240x320   196
+====== =========== ===
+
+  http://en.wikipedia.org/wiki/Pixels_per_inch
+
+lpi
+===
+
+lines per inch.
+
+  http://en.wikipedia.org/wiki/Lines_per_inch
+
+bpp
+===
+
+bits per pixel, color depth.
+
+ * 1 bpp, 2 colors (monochrome)
+ * 2 bpp, 4 colors
+ * 3 bpp, 8 colors
+ * 8 bpp, 256 colors
+ * 16 bpp, 65,536 colors ("Highcolor" )
+ * 24 bpp, 16.8 million colors ("Truecolor")
+
+  http://en.wikipedia.org/wiki/Color_depth