From c96df630460e84dcc89a069b76287b28b243c2a3 Mon Sep 17 00:00:00 2001
From: tastytea <tastytea@tastytea.de>
Date: Wed, 26 Dec 2018 23:51:32 +0100
Subject: [PATCH] Explained algorithms

---
 README.md           | 49 +++++++++++++++++++++++++++++++++++++++++++++
 src/identiconpp.hpp |  4 ++--
 2 files changed, 51 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index fb9d433..4155dec 100644
--- a/README.md
+++ b/README.md
@@ -105,3 +105,52 @@ License GPLv3: GNU GPL version 3 <https://www.gnu.org/licenses/gpl-3.0.html>.
 This program comes with ABSOLUTELY NO WARRANTY. This is free software,
 and you are welcome to redistribute it under certain conditions.
 ```
+
+## Algorithms
+
+### ltr_symmetric
+
+* Create image with width=columns, height=rows.
+* Set background color.
+* Select half of the columns, or half of the columns + 1 if uneven.
+  * `columns / 2 + columns % 2`
+* Pixels are drawn from left to right, top to bottom.
+* Use bits from digest to determine if a pixel is painted(1) or not(0).
+* Mirror the pixels vertically.
+* Use the following bits to pick the foreground color.
+* Scale image proportionally to requested width.
+
+```PLAIN
+ 0111 0011 1101 1100 […] 1111 0111 0101 0111
+^                            ^
++----------------------------+-------------->
+             |                      |
+        pixel matrix        foreground color
+```
+
+Implemented in [ltr_symmetric.cpp]
+(https://schlomp.space/tastytea/identiconpp/src/branch/master/src/ltr_symmetric.cpp)
+
+### sigil
+
+* Create image with width=columns, height=rows.
+* Set background color.
+* Select half of the columns, or half of the columns + 1 if uneven.
+  * `columns / 2 + columns % 2`
+* Pixels are drawn from top to bottom, left to right.
+* Use the first 8 bits to pick the foreground color.
+* Use the following bits to determine if a pixel is painted(1) or not(0).
+* Mirror the pixels vertically.
+* Scale image proportionally to requested width.
+
+```PLAIN
+ 0111 0011 1101 1100
+^         ^
++---------+--------->
+     |            |
+foreground color  |
+             pixel matrix
+```
+
+Implemented in [sigil.cpp]
+(https://schlomp.space/tastytea/identiconpp/src/branch/master/src/sigil.cpp)
diff --git a/src/identiconpp.hpp b/src/identiconpp.hpp
index 3b55958..5b32967 100644
--- a/src/identiconpp.hpp
+++ b/src/identiconpp.hpp
@@ -80,7 +80,7 @@ private:
     /*!
      *  @brief  Generate simple identicon.
      *
-     *          Use bits 0 to (columns / 2 + columns % 2) * _rows, use the
+     *          Use bits 0 to (_columns / 2 + _columns % 2) * _rows, use the
      *          following bits to determine foreground color. Squares are drawn
      *          from left to right, top to bottom.
      *
@@ -97,7 +97,7 @@ private:
     /*!
      *  @brief  Generate sigil identicon.
      *
-     *          Use bits 9 to (columns / 2 + columns % 2) * _rows, use the first
+     *          Use bits 9 to (_columns / 2 + _columns % 2) * _rows, use the first
      *          8 bits to determine foreground color. Squares are drawn from top
      *          to bottom, left to right.
      *