Segmentation d'images couleur par un opérateur gradient vectoriel ...

QUANTIFICATION ET MORPHOLOGIE DE PHASES DE CLINKER PAR ANALYSE D'IMAGE.
The colour of the crystals can be separated with the presented separation line (Figure 45).
The colour of alite and belite cannot be distinguished with fixed detection limits on the hue and
the saturation because of the high variance in the colour. They can not be separated automatically
with the MDFA classifier presently used because the two colour classes are not sufficiently
distant and do not verify the statistical properties needed for the MDFA. For these reasons, a
classification based on a neural network was selected. For the learning phase of the neural
network, the same database was employed as used for the texture classification. For each testwindow,
a representative colour was determined and used by the classifier. After the learning
phase, the neural network is used to class the crystal colour in the classes alite and belite.
Fusion of the classifiers
The classification of the colour and texture characteristics was made separately. The
fusion of the two complementary classifications was made by comparing of the results. If the two
classifications give the same result for a sample, the decision is accepted as final result. In the case
of a difference, using the neighbourhood grid-points makes the final decision. If a point has most
of its neighbours in a certain class, it is grouped in the same way. The neighbourhood is used in
the same way if one classifier gives no result (e.g. non-characteristic texture). The use of
associated grid points is based on the fact that each crystal includes several sample points (Figure
46). For a single point in the grid, a decision may not be possible, but it can be made including a
bigger zone. This method makes it possible to detect the major clinker phases even if there are
big variances in the colour. The compete computation time for each image is about one minute.
This is not critical because the system analyses all the images of the clinker without any operator
interaction.
User interface
The clinker analysing software includes a user interface (Figure 46) which is developed for
the Windows NT (Microsoft) environment. This interface makes it possible to easily call the
different functions such as image acquisition, crystal measurement and phase distribution
analysis. The sample image in Figure 46 is superposed with a grid of points, which were classified
in different crystal groups. The software is designed in an open way and an interactive correction
of wrong classed points is possible. It gives the free choice to the operator to accept the
classification or to modify some points.
This interface can also be used for the measurement of the crystal sizes (Figure 47). A
large number of alite and belite crystals can be measured in the different images by a simple
mouse click on the screen. For the alite crystals, it is possible to measure the length and the width
to get information about size and form of the crystals. The statistic analysis of the dimensions is
made by software and automatically printed in a standardised graphical form, which helps to
reduce the time needed for routine documentation of the results.
WORLD CEMENT RESEARCH AND DEVELOPMENT 1998 104