The ImageTest GUI
-----------------

On the left-hand side of the window, you manipulate the models.
on the right-hand side of the window, you put the image that is to be matched
against the models.

Models/test images are 8-bit greyscale images with exactly one region in white
on a black background. Think of them as presegmented images.

Walk-through:

 1) Drag circle_big.png into the left ImageView. It will get the name "Model 1"
    and appear in the ImageView.

 2) Drag circle_medium.png into the right ImageView. It will be matched against
    all the models, and the best matching model will be displayed on the left
    side (in this case, the only one that's there).
    Under the model, you can see that it says "Diff: 0.004". This is the
    difference between the model and the test image.

 3) Now click on the "<" button under the test image. This adds the test image
    as a new model named "Model 2" and rematches the test image against all
    models.
    Of course, now it matches the model that is itself exactly. The difference
    you see is 0.
    (The ">" button is the reverse. It sets the test image to the currently
    displayed model.)

 4) When there is more than one model, only the best match will be displayed.
    You can, however, choose another model in the ComboBox above the model
    image. Choose "Model 1". Note the difference.

 5) Drag cross.png into the model window. The model display switches back to the
    best match, because every time you add or remove a model, the test image is
    rematched against all models.

 6) Now click around on the small arrows next to the difference display. This
    will scroll through the list of models ordered by their difference to the
    test image.

 7) You can name the models differently by simply entering the new name into the
    ComboBox and pressing <Return>. If it's a new name, the currently displayed
    model will be renamed to it, if not, you are taken to the model with this
    name.
    Rename the big circle to "Big circle", the smaller circle to "Medium circle"
    and the cross to "Cross".

 8) Clicking on the "Remove" button will---surprise, surprise---remove the
    currently displayed model. Remove the smaller circle. The test image is
    rematched. Rematching can also be done via the "Rematch" button, but since
    it is done every time you change something significant, the button is really
    superfluous.

 9) Now add rect_vert.png as model "Rect".

10) Match rect_horiz.png by dragging it onto the test image window. You'll see
    that it matches "Rect" best. Now take a look at the standard output.
    (This can be seen in a window of the Xcode IDE entitled
    "Run - ImageTest - ImageTest - ImageTest".) The relevant line reads

 Model 4 (Rect) matches with 0.146711, rel. orient: -1.5708, rel. size: 1.3138

    This tells us that the match is pretty good and that the test image is
    rotated about -pi/2 or 90 degrees in respect to the model.

11) The "Clear" button clears the test image. Hit it.

12) Now match cross_rotated.png by dragging it onto the test image window.
    It matches "Cross" best with an orientation of 1.10984, which is about
    64 degrees.

13) You may be wondering what this "#Points: 23" means. This is the number of
    equally spaced points around the region's circumference that are used in the
    profile. The significance of this number can be demonstrated as follows:
    You should have the models big_circle.png, cross.png, and rect_vert.png as
    "Big circle", "Cross", and "Rect", respectively, and cross_rotated.png as
    the test image. The number of points should be 23. If this isn't the case,
    make it so.
    Now, change the number of points to 5. The image will be rematched and we
    see: "Big circle" matches best!
    Change the number of points to 6. Now "Cross" matches best, as expected.
    Change the number of points to 7. Guess what? "Rect" matches best.
    What's going on? This exercise is left to the reader. ;-)