# how to calculate the shape factor?

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mohd akmal masud le 29 Oct 2023
Dear All,
Anyone can help me how to calculate the shape factor for each blob on my image as attached.
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Image Analyst le 29 Oct 2023
What is your definition of shape factor?
mohd akmal masud le 30 Oct 2023
What I understand is, the shape factor is we want to know the shape of volume that have we segment.
this is descrition about the shape factor.
Shape factors are dimensionless quantities used in image analysis and microscopy that numerically describe the shape of a particle, independent of its size. Shape factors are calculated from measured dimensions, such as diameter, chord lengths, area, perimeter, centroid, moments, etc. The dimensions of the particles are usually measured from two-dimensional cross-sections or projections, as in a microscope field, but shape factors also apply to three-dimensional objects. The particles could be the grains in a metallurgical or ceramic microstructure, or the microorganisms in a culture, for example. The dimensionless quantities often represent the degree of deviation from an ideal shape, such as a circle, sphere or equilateral polyhedron.[1] Shape factors are often normalized, that is, the value ranges from zero to one. A shape factor equal to one usually represents an ideal case or maximum symmetry, such as a circle, sphere, square or cube.
the common formula is below

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### Réponses (1)

Sulaymon Eshkabilov le 30 Oct 2023
Is this what you are trying to calculate?
% Convert from RGB to gray scale
IMG_gray = rgb2gray(IMG);
% AREA
AREA = bwarea(IMG_gray)
AREA = 326.5000
% Display the minimum Feret properties of the object.
[OUT,LM] = bwferet(rgb2gray(IMG),'MinFeretProperties');
OUT.MinDiameter(1)
ans = 21.7030
OUT.MinAngle(1)
ans = 105.9454
OUT.MinCoordinates{1}
ans = 2×2
181.5000 156.5000 187.4623 135.6321
BW = imfill(rgb2gray(IMG),'holes');
CC = bwconncomp(BW);
[out,LM] = bwferet(CC,'MaxFeretProperties');
maxLabel = max(LM(:));
h = imshow(BW);
axis = h.Parent;
for labelvalues = 1:maxLabel
xmax = [out.MaxCoordinates{labelvalues}(1,1) out.MaxCoordinates{labelvalues}(2,1)];
ymax = [out.MaxCoordinates{labelvalues}(1,2) out.MaxCoordinates{labelvalues}(2,2)];
imdistline(axis,xmax,ymax);
end
title(axis,'Maximum Feret Diameter of Objects');
colorbar('Ticks',1:maxLabel)
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Sulaymon Eshkabilov le 30 Oct 2023
All details aer explained in this help documentation: https://www.mathworks.com/help/images/ref/bwferet.html#d126e43971
mohd akmal masud le 30 Oct 2023
I think this is not calculate the shape factor. it just calculate the diameter segmentation itself.

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