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Texture measures computation using PDL

by lin0 (Curate)
on Jul 12, 2007 at 14:19 UTC ( #626241=perlmeditation: print w/ replies, xml ) Need Help??

Greetings Fellow Monks,

For an image analysis application I am writing using the PDL, I needed to compute some texture measures. After some research, I decided to go with the measures proposed by Rober Haralick based on the Gray Level Co-occurrence Matrix (GLCM). To make a long story short, I found a nice tutorial on the GLCM and started implementing the code for computing the GLCM and the texture measures following the equations presented in the tutorial. This has shown me that I don't know PDL nearly as well as I would like. However, here is my first take to computing the GLCM and some of the texture measures:

#!/usr/bin/perl use warnings; use strict; use PDL; use PDL::NiceSlice; # ================================ # cooccurrence: # # $glcm = cooccurrence( $pdl, $dir, $dist, $symmetric ) # # computes the grey level coocurrence coocurrence # matrix of piddle $pdl for a given direction and # distance # # Inputs: # $pdl # $dir: direction of evaluation # $dir angle # 0 +90 # 1 +45 # 2 0 # 3 -45 # 4 -90 # $dist: distance between pixels # $symmetric: 0 => non-symmetric $glcm # # ================================ sub cooccurrence { my ( $pdl, $dir, $dist, $symmetric ) = @_; my $min_quantization_level = int( min( $pdl ) ); my $max_quantization_level = int( max( $pdl ) ); my $glcm = zeroes( $max_quantization_level - $min_quantization_level + 1 , $max_quantization_level - $min_quantization_level + 1 ); my ($dir_x, $dir_y); if ( $dir == 0 ){ $dir_x = 0; $dir_y = 1; } elsif ( $dir == 1 ){ $dir_x = 1; $dir_y = 1; } elsif ( $dir == 2 ){ $dir_x = 1; $dir_y = 0; } elsif ( $dir == 3 ){ $dir_x = 1; $dir_y = -1; } elsif ( $dir == 4 ){ $dir_x = 0; $dir_y = -1; } else { $dir_x = 0; $dir_y = 0; } $dir_x *= $dist; $dir_y *= $dist; my $glcm_ind_x = 0; my $glcm_ind_y = 0; foreach my $grey_level_1 ( $min_quantization_level .. $max_quantiz +ation_level ){ my ( $ind_x_1, $ind_y_1 ) = whichND( $pdl == $grey_level_1 ); $ind_x_1 += $dir_x; $ind_y_1 += $dir_y; foreach my $grey_level_2 ( $min_quantization_level .. $max_qua +ntization_level ){ my ( $ind_x_2, $ind_y_2 ) = whichND( $pdl == $grey_level_2 ); my $count = 0; foreach my $i (0..$ind_x_1->getdim(0) - 1) { foreach my $j (0..$ind_x_2->getdim(0) - 1) { if ( ($ind_x_1($i) == $ind_x_2($j)) and ($ind_y_1($i) == $ind_y_2($j)) ) { $count++; } } } $glcm( $glcm_ind_x, $glcm_ind_y ) .= $count; $glcm_ind_y++; } $glcm_ind_y = 0; $glcm_ind_x++; } if ( $symmetric ) { $glcm += transpose( $glcm ); } $glcm /= sum( $glcm ); return $glcm; } # ================================ # texture_descriptors: # # ( $contrast, $dissimilarity, $homogeneity # , $inverse_difference, $asm, $energy ) # = texture_descriptors( $glcm ); # # computes a set of texture descriptors # associated with the GLCM $glcm # # $contrast: # Range = [0 .. ($glcm->getdim(0)-1)^2] # $contrast = 0 for a constant image. # $homogeneity: # Measures the closeness of the distribution # of elements in the GLCM to the GLCM diagonal. # Range = [0 1] # $homogeneity is 1 for a diagonal GLCM. # ================================ sub texture_descriptors{ my $glcm = pdl( @_ ); my $n = $glcm->getdim(0); my $i = sequence( $n ); my $j = sequence( $n ); my $diff = $i->dummy(0, $n) - $j->dummy(1, $n); my $contrast = sum( $glcm * ($diff ** 2) ); my $dissimilarity = sum( $glcm * abs( $diff ) ); my $homogeneity = sum( $glcm / ( 1 + $diff ** 2) ); my $inverse_difference = sum( $glcm / ( 1 + abs( $diff ) ) ); my $asm = sum( $glcm ** 2 ); my $energy = sqrt( $asm ); return ( $contrast, $dissimilarity, $homogeneity , $inverse_difference, $asm, $energy ); } my $pdl = pdl([0,0,1,1],[0,0,1,1],[0,2,2,2],[2,2,3,3]); my $glcm = cooccurrence( $pdl, 2, 1, 1 ); print "glcm: $glcm\n"; my ( $contrast, $dissimilarity, $homogeneity , $inverse_difference, $asm, $energy ) = texture_descriptors( $glcm ); print "contrast: $contrast\tdissimilarity: $dissimilarity\n"; print "homogeneity: $homogeneity\t"; print "inverse difference: $inverse_difference\n"; print "ASM: $asm\tenergy: $energy\n";

I still have a lot more work to do, but feel free to go ahead and share with us your approach for finding these or the remaining texture measures.

Cheers,

lin0

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