Adds OpenCV tips

opencv.md

@@ -0,0 +1,68 @@
+# OpenCV
+
+Memos and Tips about the OpenCV library.
+
+## In C/C++:
+
+### Placing a pointer to the beginning of pixel in an image:
+
+Can be used to naviguate through pixels easily (and more efficiently than some openCV functions).
+
+```C
+char *pImage = iplImage->ImageData
+```
+
+
+### Short review of the IplImage structure:
+
+What’s really needed to work with an Image
+```C
+* IplImage struct {
+    depth # Number of channels (gray level, color, . . .)
+    sizeX
+    sizeY
+    * ImageData } #Pixels of the image
+    ...}
+```
+
+
+### Simple tips for Image Processing optimization in C:
+
+An image is stored in a memory a a long line (n*m size)
+
+Always go __trough the buffer way__, and not the opposite!
+```C
+for (i in nb_lines):
+    for (j in nb_cols):
+        //do stuff
+    }
+}
+```
+
+and
+
+```C
+for (j in nb_cols):
+    for (i in nb_lines):
+        //do stuff
+    }
+}
+```
+
+are different ! **The second one is 10% faster than the other !**
+
+##In Python :
+
+Error on compiling OpenCV with Python bindings:
+
+If you get this error when trying to compile OpenCV in Linux
+```bash
+Could NOT find PythonLibs (missing: PYTHON_INCLUDE_DIRS) in cmake
+```
+
+Simply try installing python-dev packages.
+```bash
+$ sudo apt-get install python-dev
+```
+
+It should solve the problem.

subversion.md

@@ -12,6 +12,7 @@ $ svn cp trunk -> new_branch
 ```bash
 $ svn update
 ```
+
 __**NOTE:** The command is an update and not a commit, as this is the server who performed the operation!__
 
 You’re done!