MorphoGraphs and Imagery - Practical session 5

Goals

Knowing how to apply morphological operators by structuring elements and morphological connected operators to binary and grayscale images thanks to Pink library
Understanding the effect of basic morphological operators by structuring elements and of morphological connected operators on binary and grayscale images
Knowing how to compose morphological operators to solve some typical problems of binary and grayscale image processing

General Instructions

Solve each problem of the session step by step, following the provided guidelines. Note that there can be multiple solutions.
For each problem, use the operators (and the programs) given in the associated 'tools' section. These programs must be called from a Linux terminal under the environment settled for the course MorphoGraph and Imagery. Use the provided links to access documentation.
For each problem, save in a text file (a shell script) the series of commands that you use.
If you do not have time to answer all items during the session, remaining items must be solved as homework after the session. Note that you should send your solution to Problem 3 leading to bonus/malus on your final evaluation of the course.
Read the whole description of a problem before starting to look for a solution.

Bon Courage :)

Problem 1 (without a computer): connected filtering a synthetic image
Let F be the following image:

1A - Represent the k-section F_k of F with k=0,...,9
1B - Label the connected components of F (letters can be used as labels), assuming that the image is equipped with the 4-adjacency Γ₄
1C - Draw the component tree of F
1D - Simplify the image F by iteratively razing the maxima of minimal area, until the image contains a unique maxima
1E - Same as 1D, but according to depth
1F - Same as 1D, but according to volume
1G - Draw the unique maximum of the image obtained in 1F

Preliminary problem (using a computer)

Before going any further, download the file PS5-Images.tgz and uncompress it

tar -xvzf PS5-Images.tgz

This archive contains the images that will be used during the session.

Problem 2: extracting the lobes of cil.pgm

INPUT: cil.pgm	DESCRIPTION OF THE PROBLEM	EXPECTED RESULT (2B)
	The image cil.pgm represents a slice of a cell. In order to know whether this cell is sane or not, it is important to perform a geometrical analysis of the visible bright lobes. In order to perform such analysis, one usually starts by finding the spatial extension of these bright lobes. Problem 2 is about extracting (localizing) the bright lobes of image cil.pgm.

Guideline.

2A - Try to extract the "significant" blobs by thresholding (without using a morphological operator)
2B - Extract the "significant" blobs: produce an image like the one above on the right
2C - Same as 2B, but using the operators of the section 'Extra tools.' below

Tools.
You can use any tool presented for the previous problems (in this session and in the previous one). In addition, you can also use the following ones:

'seuil' (NB: seuil means threshold in French)
'seuil.tcl' (an interactive version of seuil)
'areaopening', 'areaclosing', 'areaopening.tcl', 'areaclosing.tcl'
'heightmaxima', 'heightminima'
'volmaxima'
'maxima', 'minima'

Extra tools. (for solving item 2C)

'heightselnb', 'heightselnb.tcl'
'areaselnb'
'volselnb'
'inverse'

Problem 3: cleaning image s.pgm

Important remark: Your have to send me your solution by e-mail before the next practical session. Your solution must be sent in the form of four scripts that solve items 3A, 3B, 3C, and 3D respectively. Depending of the quality of your solution, a bonus/malus that ranges from -2 to +2 points will be applied to your final grade of the course MorphoGraph and Imagery.

INPUT: s.pgm	DESCRIPTION OF THE SITUATION	EXPECTED RESULT (2D)
	You get the picture s.pgm that was taken with a digital camera. Before displaying the depicted building in a new website dedicated to New-York architecture, the picture must be processed. Indeed, for aesthetic reasons, salt and pepper noise must be removed, and for copyright reasons, the name of the company that owns the building must be hidden. Problem 3 is about cleaning image s.pgm.

Guideline.

3A - Remove salt and pepper noise (see the expected result for problem 6B of the previous session)
3B - Extract the writings from the image obtained after 3A
3C - Produce a patch (an image) such that the white pixels of the image obtained in 3B are replaced by gray pixels of intensity similar to the one of their "neighbors" that do not belong to the bright writings
3D - Combine the result of 2A, 2B, and 2C to obtain an image that looks like s.pgm but without salt and pepper noise and where the bright letters are no more visible: produce an image like the one above on the right

Tools.
You can use any tool presented for the previous problems (in this session and in the previous one). In addition, you can also use the following one:

'convexhull '

This practical session was prepared by Jean Cousty
Laboratoire d'Informatique Gaspard-Monge, Université Paris-Est - Département Informatique, ESIEE Paris