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

QUANTIFICATION ET MORPHOLOGIE DE PHASES DE CLINKER PAR ANALYSE D'IMAGE.
Figure 43 shows an example of a pore filled with the epoxy resin and also a not saturated
pore. The detection limits are drawn with a black colour.
Figure 43. - Segmentation of the pores within detected limits.
Differentiation of alite and belite
As explained in the introduction, colour and texture must be included as parameters of
state for the segmentation of alite and belite. An exact description of the surface is thus required
to enable an accurate distinction between the two crystals. Two methods were examined for these
investigations:
• Local statistic texture analysis and classification.
• Local colour analysis and non-linear classification.
In the end, the fusion of the two classifications gives the final decision.
Local analysis
A grid of about 400 regularly spaced points is superposed on the image in order to
simulate the model of the classic point counting. The points belonging to regions already
classified are separated. For the others in alite and belite, the algorithm chooses a neighbourhood
for the local characterisation. A local window is searched that is completely included in a crystal.
The window size is limited to 32*32 pixels (~5*5µm).
Texture analysis [Anwander et al., 1997]
The belite differs from the alite by its very textured surface. Texture describes some local
order repeated over a region or the analysing window. Based on the idea of statistic texture
analysis of Haralick [Haralick, 1979], our method extracts features to characterise the local
texture. These features hold the most important information about the texture and are used for
the classification. The local characterisation of the texture gives measurements about the
irregularity, coarseness (related to the spatial repetition period of the local structure: when this
period increases, the texture varies from fine to coarse) or 'busyness' (great variability of grey
WORLD CEMENT RESEARCH AND DEVELOPMENT 1998 101