Added an initial version of a texton module that represents the appea… (

#1692)

* Added an initial version of a texton module that represents the appearance of an image with a texton distribution

In past work, we have used texton distributions for instance for obstacle detection. If the entropy of the texton distribution becomes low, this is typically an indication of a close obstacle. This "appearance variation cue" can be a good complement to using optical flow measurements for obstacle avoidance. There are may other uses for texton distributions though, while they are computationally quite cheap.
* Fixed code style, and added nicer settings and documentation in xml

conf/modules/cv_textons.xml

@@ -0,0 +1,49 @@
+<!DOCTYPE module SYSTEM "module.dtd">
+
+<module name="cv_textons" dir="computer_vision">
+  <doc>
+    <description>Represent the appearance (texture, color) of an image by means of a texton histogram.</description>
+
+    <section name="TEXTONS" prefix="TEXTONS_">
+      <define name="LOAD_DICTIONARY" value="YES" description="Whether a dictionary is loaded (YES) or learned (NO)."/>
+      <define name="N_TEXTONS" value="20" description="The number of textons (words) in the dictionary."/>
+      <define name="PATCH_SIZE" value="6" description="Size of the image patches extracted from the image - even numbers."/>
+      <define name="FULL_SAMPLING" value="NO" description="If YES, the entire image is covered with samples, if NO sub-sampling is used (faster)."/>
+      <define name="DICTIONARY_NUMBER" value="0" description="Number of the dictionary (so that different environments can each have their specific dictionary)."/>
+      <define name="ALPHA" value="10" description="Learning rate when creating the dictionary: 0 = no learning, 255 = the texton becomes equal to the new patch."/>
+      <define name="N_SAMPLES_IMAGE" value="50" description="Number of samples extracted form the image when not doing full sampling."/>
+      <define name="N_LEARNING_SAMPLES" value="10000" description="Number of samples used for learning the dictionary."/>
+      <define name="BORDER_WIDTH" value="0" description="Width of the image border from which no samples are taken."/>
+      <define name="BORDER_HEIGHT" value="0" description="Height of the border from which no samples are taken."/>
+    </section>
+
+  </doc>
+
+  <settings>
+    <dl_settings>
+      <dl_settings NAME="Textons">
+        <dl_setting var="load_dictionary" min="0" step="1" max="1" module="computer_vision/textons" shortname="load dict." values="NO|YES" param="TEXTONS_LOAD_DICTIONARY"/>
+        <dl_setting var="n_textons" min="1" step="1" max="255" shortname="n_textons" param="TEXTONS_N_TEXTONS"/>
+        <dl_setting var="patch_size" min="2" step="2" max="40" shortname="p_size" param="TEXTONS_PATCH_SIZE" />
+        <dl_setting var="FULL_SAMPLING"  min="0" step="1" max="1" shortname="full_sam" values="NO|YES" param="TEXTONS_FULL_SAMPLING" />
+        <dl_setting var="dictionary_number"  min="0" step="1" max="20" shortname="dict_num" param="TEXTONS_DICTIONARY_NUMBER" />
+        <dl_setting var="n_samples_image"  min="0" step="10" max="1000" shortname="n_samples" param="TEXTONS_ALPHA" />
+        <dl_setting var="n_learning_samples"  min="1" step="100" max="250000" shortname="n_l_samples" param="TEXTONS_N_LEARNING_SAMPLES" />
+        <dl_setting var="alpha" min="0" step="1" max="255" shortname="alpha" param="TEXTONS_ALPHA"/>
+        <dl_setting var="border_width"  min="0" step="1" max="200" shortname="b_w" param="TEXTONS_BORDER_WIDTH"/>
+        <dl_setting var="border_height"  min="0" step="1" max="200" shortname="b_h" param="TEXTONS_BORDER_HEIGHT"/>
+      </dl_settings>
+    </dl_settings>
+  </settings>
+
+  <header>
+    <file name="textons.h"/>
+  </header>
+  <init fun="textons_init()"/>
+
+  <makefile>
+    <file name="textons.c"/>
+    <file name="image.c" dir="modules/computer_vision/lib/vision"/>
+  </makefile>
+</module>
+