add regionElementCounts.m

Author: dlegland

src/@Image/regionElementCounts.m

@@ -0,0 +1,39 @@
+function [counts, labels] = regionElementCounts(obj, varargin)
+% Count the number of pixels/voxels within each region of a label image.
+%
+%   output = regionElementCounts(input)
+%
+%   Example
+%   regionElementCounts
+%
+%   See also
+%
+ 
+% ------
+% Author: David Legland
+% e-mail: david.legland@inrae.fr
+% INRAE - BIA Research Unit - BIBS Platform (Nantes)
+% Created: 2020-12-02,    using Matlab 9.8.0.1323502 (R2020a)
+% Copyright 2020 INRAE.
+
+% check input type
+if ~isLabelImage(obj)
+    error('Requires a label image as input');
+end
+
+% determine labels
+if isempty(varargin)
+    labels = unique(obj.Data(:));
+    labels(labels==0) = [];
+else
+    labels = varargin{1};
+end
+
+% allocate memory
+nLabels = length(labels);
+counts = zeros(nLabels, 1);
+
+% iterate over labels and count elements
+for i = 1:nLabels
+    counts(i) = sum(obj.Data(:) == labels(i));
+end

tests/image/test_regionElementCounts.m

@@ -0,0 +1,54 @@
+function tests = test_regionElementCounts
+% Test suite for the file regionElementCounts.
+%
+%   Test suite for the file regionElementCounts
+%
+%   Example
+%   test_regionElementCounts
+%
+%   See also
+%     regionElementCounts
+
+% ------
+% Author: David Legland
+% e-mail: david.legland@inrae.fr
+% Created: 2020-12-02,    using Matlab 9.8.0.1323502 (R2020a)
+% Copyright 2020 INRAE - BIA-BIBS.
+
+tests = functiontests(localfunctions);
+
+function test_2d(testCase) %#ok<*DEFNU>
+% Count the elements in a label image with 4 regions.
+
+data = zeros(10, 10);
+data(2, 2) = 1;
+data(2, 4:8) = 3;
+data(4:8, 2) = 4;
+data(4:8, 4:8) = 9;
+img = Image('Data', data, 'Type', 'label');
+
+counts = regionElementCounts(img);
+
+assertEqual(testCase, length(counts), 4);
+assertEqual(testCase, counts, [1 5 5 25]');
+
+
+function test_3d(testCase) %#ok<*DEFNU>
+% Count the elements in a label image with 4 regions.
+
+data = zeros(10, 10, 10);
+data(2, 2, 2) = 1;
+data(4:8, 2, 2) = 3;
+data(2, 4:8, 2) = 4;
+data(2, 2, 4:8) = 5;
+data(4:8, 4:8, 2) = 10;
+data(4:8, 2, 4:8) = 12;
+data(2, 4:8, 4:8) = 15;
+data(4:8, 4:8, 4:8) = 19;
+img = Image('Data', data, 'Type', 'label');
+
+counts = regionElementCounts(img);
+
+assertEqual(testCase, length(counts), 8);
+assertEqual(testCase, counts, [1  5 5 5  25 25 25  125]');
+