computeBrightFraction

 compute brightness fraction for particle

  Syntax: brightFraction = computeBrightFraction(image, cartX, cartY)

 This function takes the original image together with a boundary curve
   structure (bnd) to do the following. First, extract the sub image of
   the particle. Secondly compute a circular filter that selects about 70%
   of the center area. Thirdly, apply a threshold to this part and
   calculate the fraction of bright pixels by total pixels of the cneter
   area.

 If required a modified image is returned in a second output argument.
   This image leaves the center area as it was provided and inverts the
   outer area.

 The brightnes fraction is used to identify bubbles. Therefore, the
   roundness value is also required.

 See also: obtainBnd

• obtainBnd create boundary data structure from raw data

0001 function [brightFraction particleImageOut] = ...
0002     computeBrightFraction(image, cartX, cartY, sizeFraction, threshold)
0003 % compute brightness fraction for particle
0004 %
0005 %  Syntax: brightFraction = computeBrightFraction(image, cartX, cartY)
0006 %
0007 % This function takes the original image together with a boundary curve
0008 %   structure (bnd) to do the following. First, extract the sub image of
0009 %   the particle. Secondly compute a circular filter that selects about 70%
0010 %   of the center area. Thirdly, apply a threshold to this part and
0011 %   calculate the fraction of bright pixels by total pixels of the cneter
0012 %   area.
0013 %
0014 % If required a modified image is returned in a second output argument.
0015 %   This image leaves the center area as it was provided and inverts the
0016 %   outer area.
0017 %
0018 % The brightnes fraction is used to identify bubbles. Therefore, the
0019 %   roundness value is also required.
0020 %
0021 % See also: obtainBnd
0022 
0023 % The elk-library: convex geometry applied to crystallization modeling.
0024 %   Copyright (C) 2012 Alexander Reinhold
0025 %
0026 % This program is free software: you can redistribute it and/or modify it
0027 %   under the terms of the GNU General Public License as published by the
0028 %   Free Software Foundation, either version 3 of the License, or (at your
0029 %   option) any later version.
0030 %
0031 % This program is distributed in the hope that it will be useful, but
0032 %   WITHOUT ANY WARRANTY; without even the implied warranty of
0033 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
0034 %   General Public License for more details.
0035 %
0036 % You should have received a copy of the GNU General Public License along
0037 %   with this program.  If not, see <http://www.gnu.org/licenses/>
0038 
0039 % get particle image
0040 particleImage = image(max(cartY):-1:min(cartY), ...
0041                       min(cartX):max(cartX));
0042 
0043 % size and coordinates
0044 xSize = size(particleImage, 1);
0045 ySize = size(particleImage, 2);
0046 xCenter = round(xSize/2);
0047 yCenter = round(ySize/2);
0048 
0049 % construct filter
0050 [Y X] = meshgrid(1:ySize, 1:xSize);
0051 filterImage = sqrt((X-xCenter).^2 + (Y-yCenter).^2) < ...
0052               0.5*sizeFraction*min([xSize ySize]);
0053 imageFiltered = (particleImage > threshold) & filterImage;
0054 
0055 % apply filter to brightness fraction
0056 brightFraction  = sum(imageFiltered(:)) / sum(filterImage(:));
0057 
0058 % return image if required
0059 if nargout == 2
0060     particleImageOut = ...
0061     uint8(particleImage) .* uint8(filterImage) + ...
0062     uint8(255 - particleImage) .* uint8(~filterImage);
0063 end
0064 
0065