Lab Exercise: Installation of Software and Data
===============================================

OpenCV
------

Installing OpenCV is not trivial. You can download binary
distributions and install them but it is not always clear that all we
need is packaged. For the course we need the module containing the
non-free SIFT software.

I am using the anaconda Python distribution. I didn't install the
standard OpenCV but i got a version from binstar::

   conda install -c https://conda.binstar.org/menpo opencv3

If all went well you must be able to run the following code:

.. ipython:: python

   import cv2

   x = np.arange(128)-64
   X, Y = np.meshgrid(x,x)
   f = (100*(np.hypot(X,Y)<32)).astype(np.uint8)
   
   plt.clf()
   plt.imshow(f);
   plt.gray()

   sift = cv2.xfeatures2d.SIFT_create()
   kps, dscs = sift.detectAndCompute(f, mask=None)
   
   ax = plt.gca()
   for kp in kps:
       ax.add_artist( plt.Circle((kp.pt), kp.size/2, color='green', fill=False))
   
   @savefig siftdetect.png width=10cm
   plt.show()

No worries (yet) in case you have a hard time understanding what is
done in this code fragment. If you get an image that looks like the
one above you have correctly installed OpenCV.


Standard Images and Data Sets
-----------------------------

In the lab exercises you will need some standard data files. All these
files are collected in one directory on the web.

Skin Color Data Set
...................

- :download:`SkinColor.zip</resources/SkinColor.zip>`

Standard Images
...............

Below are some standard images used a lot in image processing
research. The images shown here a small images ($256\times256$) which
is an advantage when experimenting with code in development.

You can download these images by clicking right on an image.

----

.. figure:: /images/trui.png
   :align: center

   The girl from an advertisement. This image is used a lot
   by researchers (originally) from Delft University. It is a nice
   image to use because it contains a lot of details. 

----

.. figure:: /images/colortrui.png
   :align: center
   :width: 256px

   The same girl from the advertisement, this time in color. Note that
   this is NOT the color version of the same image as shown in
   gray. Also note that this is scanned copy of a printed image. If
   you look up close you can see the primary color dots.

----

.. figure:: /images/cameraman.png
   :align: center

   The camera man image. Originally used by researchers in the field
   of image and video compression.

----

.. figure:: /images/schema.jpg
   :align: center

   A hand drawn scheme of an electrical circuit. Nowadays most of the
   technical line drawings are made with computers. In the past most
   of these drawings were made by hand. Considerable effort has been
   made to automatically digitize these line drawings into vector
   graphics formats (i.e. not a simple sampled version of the scanned
   drawing but a version were lines are recognized and stored as
   lines).

----

.. figure:: /images/nachtwacht1.jpg
   :align: center

   A picture of a small part of the famous 'Nachtwacht' painting by
   Rembrandt van Rijn. Together with the nachtwacht2.jpg image this
   image is used as an example for building image mosaics.

.. figure:: /images/nachtwacht2.jpg
   :align: center


----

.. figure:: /images/calibrationpoints.jpg
   :align: center
   :width: 400px

   A 2D projection of a 3D object. The checkerboards provide the data
   to calibrate the camera.


.. figure:: /images/view1.jpg
   :align: center
   :width: 400px

   A view of the same calibration object and a cudly animal next to
   it. There are several views on this scene available:
   :download:`/images/view1.jpg`, :download:`/images/view2.jpg`,
   :download:`/images/view3.jpg`, :download:`/images/view4.jpg`.


----

.. figure:: /images/peppers.png
   :align: center
   :width: 400px

   peppers.png. Nice bright colors...


-----

.. figure:: /images/lena.jpg
   :align: center
   :width: 10px

   Lena. I am aware of the controversy produced by the use of this
   image in image processing papers (see `Wikipedia
   <https://en.wikipedia.org/wiki/Lenna>`_). This image is refered to
   here because of its historic relevance.

-----

.. figure:: /images/flyeronground.png
   :align: center
   :width: 400px

   A flyer of size A4 lying on the ground and photographed at an angle
   from above. The flyer is perspectivily distorted.


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