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

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QUANTIFICATION ET MORPHOLOGIE DE PHASES DE CLINKER PAR ANALYSE D'IMAGE. (a) (b) (c) Figure 42. - Segmentation of the matrix: (a) sample image, (b) binary image, (c) matrix segmentation Segmentation of the pores The polished clinker shows two types of pores: • Pores that are completely filled with the epoxy resin during the clinker preparation. • Pores that are filled with the polishing product that reflect the light very much. Two segmentation algorithms for these two types of pores were developed. • Pores filled with the epoxy resin: the filled pores present a homogeneous and unstructured surface because the resin is not crystalline. It is uncoloured and forms a grey area with a middle brightness. The homogeneity can be described by using the gradient of the image. A homogeneous image has a constant gradient of zero. By extracting the homogeneous regions in the image which have a minimum size and which are uncoloured, the epoxy resin can be separated from the crystals. • Not saturated pores: the agent used to polish the sample fills up the not saturated pores. This causes a very bright area, which is getting continuously darker to the borders of the pore. The algorithm takes advantage of these properties and looks for the central zone, which is bright and homogeneous. Once detected, the area is expanded by adding the border-points until the relatively dark limits of the crystals are reached. WORLD CEMENT RESEARCH AND DEVELOPMENT 1998 100
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
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N° d’ordre 2001ISAL0062 Année 2
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TABLE DES MATIERES. 3. Gradient cou
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TABLE DES MATIERES. La cuisson et l
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INTRODUCTION GENERALE. Le Clinker e
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Chapitre 2 INTRODUCTION AU TRAITEME
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INTRODUCTION AU TRAITEMENT D'IMAGES
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Chapitre 3 GRADIENT COULEUR MULITEC
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GRADIENT COULEUR MULITECHELLE (GCM)
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Page 49 and 50: GRADIENT COULEUR MULITECHELLE (GCM)
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Segmentation d'images couleur par un opérateur gradient vectoriel ...

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