Downloads :
polydisperse.jpg
centers_list.m
vertex_edges_cells.m
From images to centers of bubbles
The programs in this section extract the cellular structure of a foam in terms of the bubble centers, walls, and vertices. A sample image
(polydisperse.jpg:download) is used to illustrate the working of
the first module of the code. In this module (centers_list.m:download), the raw image is cropped, filtered and the center positions of the bubbles
are extracted. All subsequent modules do not require the initial image.
The above two images are displayed by the commmand :
> P=centers_list;
'P' is a (number of cells)x4 matrix.
Column 1 : Integer label for individual cells in image.
Column 2 : X component of center of corresponding cell.
Column 3 : Y component of center of corresponding cell.
Column 4 : Area corresponding to a cell in the binary image extracted from raw image.
Edges and Vertices of cells
The cell center positions are used to construct a Voronoi diagram (vertex_edges_cells.m:download)that captures the position of the cell walls with reasonable accuracy.
The boundary cells are not well represented in this setup, and neither are structures that are not completely space filling. The following
commands brings up the next image :
> center_positions=P(:,[2 3]);
> [V,E,C,bdry_cells]=vertex_edges_cells(center_positions);
'V' is a two-column matrix with the x-y positions of the vertices.
'E' is a two-column matrix comprising the list of vertices forming edges in the interior of the cellular network.
'C' is a cell-array listing n-vertices forming a cell. The sequence in the array is the same as Column 1 of 'P' above.
'bdry_cells' is a vector of integers corresponding to labels of cells whose vertices lie at the boundary in the Voronoi construction.
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