XML reader erbij

docs/verslag.tex

@@ -206,11 +206,38 @@ choices we made.
 In order to retrieve the license plate from the entire image, we need to
 perform a perspective transformation. However, to do this, we need to know the 
 coordinates of the four corners of the licenseplate. For our dataset, this is
-stored in XML files. So, the first step is to read these XML files.\\
-\\
-\paragraph*{XML reader}
+stored in XML files. So, the first step is to read these XML files.
 
+\paragraph*{XML reader}
 
+The XML reader will return a 'license plate' object when given an XML file. The
+licence plate holds a list of, up to six, NormalizedImage characters and from which country the
+plate is from. The reader is currently assuming the XML file and image name are corresponding. Since this was the case
+for the given dataset. This can easily be adjusted if required. 
+
+To parse the XML file, the minidom module is used. So the XML file can be
+treated as a tree, where one can search for certain nodes. In each XML
+file it is possible that multiple versions exist, so the first thing the reader will do is
+retrieve the current and most up-to-date version of the plate. The reader will only get results from this
+version.
+
+Now we are only interested in the individual characters so we can skip the location
+of the entire license plate. Each character has 
+a single character value, indicating what someone thought what the letter or digit was and four coordinates to create
+a bounding box. To make things not to complicated a 
+Character class and Point class are used. They
+act pretty much as associative lists, but it gives extra freedom on using the
+data. If less then four points have been set the character will not be saved.
+
+When four points have been gathered the data from the actual image is being requested. 
+For each corner a small margin is added (around 3 pixels) so that no features will be lost and minimum
+amounts of new features will be introduced by noise in the margin. 
+
+In the next section you can read more about the perspective transformation that is being done. After the transformation the
+character can be saved: Converted to grayscale, but nothing further. This was used
+to create a learning set. If it doesn't need to be saved as an actual image it will be converted
+to a NormalizedImage. When these actions have been completed for each character the license
+plate is usable in the rest of the code.
 
 \paragraph*{Perspective transformation}
 Once we retrieved the cornerpoints of the license plate, we feed those to a