# $Id: Morphology.pm,v 1.7 2007/08/21 12:56:55 dk Exp $ package IPA::Morphology; use strict; require Exporter; use vars qw( $VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS $AUTOLOAD %transform_luts ); @ISA = qw(Exporter); $VERSION = '0.02'; @EXPORT = qw(); @EXPORT_OK = qw(BWTransform dilate erode opening closing algebraic_difference gradient reconstruct watershed thinning); %EXPORT_TAGS = (binary => [qw(BWTransform)]); sub opening { my $in = shift; my $out = erode($in,@_); $out = dilate($out,@_); $out-> name( "IPA::Morphology::opening"); return $out; } sub closing { my $in = shift; my $out = dilate($in,@_); $out = erode($out,@_); $out-> name( "IPA::Morphology::closing"); return $out; } sub gradient { my $img = shift; my $out = dilate($img,@_); my $erode = erode($img,@_); return algebraic_difference($out,$erode,inPlace=>'Yes'); } sub AUTOLOAD { my ($subname)=$AUTOLOAD; $subname=~s/^IPA::Morphology:://; if ($subname=~/^bw_/) { my ($bwmethodname)=($subname); $bwmethodname=~s/^bw_//; if (ref($transform_luts{$bwmethodname}) eq 'CODE') { my ($lut)=$transform_luts{$bwmethodname}->(); eval("sub $subname { return BWTransform(\$_\[0\],lookup=>\'$lut\'); }"); croak("IPA::Morphology::AUTOLOAD: $@") if $@; goto &$subname; } else { croak("IPA::Morphology: internal error - not a code reference in hash for $bwmethodname"); } } else { croak("IPA::Morphology: unknown method $AUTOLOAD called"); } } sub X0 { return ($_[0] & 0x001 ? 255 : 0); }; sub X1 { return ($_[0] & 0x002 ? 255 : 0); }; sub X2 { return ($_[0] & 0x004 ? 255 : 0); }; sub X3 { return ($_[0] & 0x008 ? 255 : 0); }; sub X4 { return ($_[0] & 0x010 ? 255 : 0); }; sub X5 { return ($_[0] & 0x020 ? 255 : 0); }; sub X6 { return ($_[0] & 0x040 ? 255 : 0); }; sub X7 { return ($_[0] & 0x080 ? 255 : 0); }; sub X8 { return ($_[0] & 0x100 ? 255 : 0); }; %transform_luts=( dilate => sub { my ($rstr)=""; my ($i); for ($i=0; $i<512; $i++) { $rstr.=chr(X0($i) | X1($i) | X2($i) | X3($i) | X4($i) | X5($i) | X6($i) | X7($i) | X8($i)); } return $rstr; }, erode => sub { my ($rstr)=""; my ($i); for ($i=0; $i<512; $i++) { $rstr.=chr(X0($i) & X1($i) & X2($i) & X3($i) & X4($i) & X5($i) & X6($i) & X7($i) & X8($i)); } return $rstr; }, isolatedremove => sub { my ($rstr)=""; my ($i); for ($i=0; $i<512; $i++) { $rstr.=chr(X0($i) & (X1($i) | X2($i) | X3($i) | X4($i) | X5($i) | X6($i) | X7($i) | X8($i))); } return $rstr; }, togray => sub { my ($rstr)=""; my ($i); for ($i=0; $i<512; $i++) { $rstr.=chr((X0($i)+X1($i)+X2($i)+X3($i)+X4($i)+X5($i)+X6($i)+X7($i)+X8($i))/9); } return $rstr; }, invert => sub { my ($rstr)=""; my ($i); for ($i=0; $i<512; $i++) { $rstr.=chr(255-X0($i)); } return $rstr; }, prune => sub { my @ret = ((0, 255) x 256); # ident $ret[$_] = 0 for map { my $x = 1; $x |= 1 << $_ for split ''; $x; } # 0-connected (isolated) 0, # 1-connected 1,2,3,4,5,6,7,8, # 2-joint-connected 12,23,34,45,56,67,78, # 3-joint connected 234,456,678,812 ; return join '', map { chr } @ret; }, break_node => sub { my @ret = ((0, 255) x 256); # ident my @nodes = map { my $x = 1; $x |= 1 << $_ for split ''; $x; } # 3-connected 135, 246, 357, 468, 571, 682, 713, 824, 146, 257, 368, 471, 582, 613, 724, 835, # 4-connected 1357, 2468 ; for ( 0..511) { my $ix = $_; for ( @nodes) { next unless ($_ & $ix) == $_; $ret[$ix] = 0; last; } } return join '', map { chr } @ret; }, ); 1; __DATA__ =pod =head1 NAME IPA::Morphology - morphological operators =head1 DESCRIPTION Quote from L: Morphological operators often take a binary image and a structuring element as input and combine them using a set operator (intersection, union, inclusion, complement). They process objects in the input image based on characteristics of its shape, which are encoded in the structuring element. Usually, the structuring element is sized 3x3 and has its origin at the center pixel. It is shifted over the image and at each pixel of the image its elements are compared with the set of the underlying pixels. If the two sets of elements match the condition defined by the set operator (e.g. if the set of pixels in the structuring element is a subset of the underlying image pixels), the pixel underneath the origin of the structuring element is set to a pre-defined value (0 or 1 for binary images). A morphological operator is therefore defined by its structuring element and the applied set operator. Morphological operators can also be applied to gray-level images, e.g. to reduce noise or to brighten the image. =over =item BWTransform IMAGE [ lookup ] Applies 512-byte C LUT string ( look-up table ) to image and returns the convolution result ( hit-and-miss transform). Each byte of C is a set of bits, each corresponding to the 3x3 kernel index: |4 3 2| |5 0 1| |6 7 8| Thus, for example, the X-shape would be represented by offset 2**0 + 2**2 + 2**4 + 2**6 + 2**8 = 341 . The byte value, corresponding to the offset in C string is stored in the output image. C defines several basic LUT transforms, which can be invoked by the following code: IPA::Morphological::bw_METHOD( $image); or its alternative IPA::Morphology::BWTransform( $image, lookup => $IPA::Morphology::transform_luts{METHOD}->()); Where METHOD is one of the following string constants: =over =item dilate Morphological dilation =item erode Morphological erosion =item isolatedremove Remove isolated pixels =item togray Convert binary image to grayscale by applying the mean filter =item invert Inversion operator =item prune Removes 1-connected end points =item break_node Removes node points that connect 3 or more lines =back Supported types: Byte =item dilate IMAGE [ neighborhood = 8 ] Performs morphological dilation operation on IMAGE and returns the result. C determines whether the algorithm assumes 4- or 8- pixel connectivity. Supported types: Byte, Short, Long, Float, Double =item erode IMAGE [ neighborhood = 8 ] Performs morphological erosion operation on IMAGE and returns the result. C determines whether the algorithm assumes 4- or 8- pixel connectivity. Supported types: Byte, Short, Long, Float, Double =item opening IMAGE [ neighborhood = 8 ] Performs morphological opening operation on IMAGE and returns the result. C determines whether the algorithm assumes 4- or 8- pixel connectivity. Supported types: Byte, Short, Long, Float, Double =item closing IMAGE [ neighborhood = 8 ] Performs morphological closing operation on IMAGE and returns the result. C determines whether the algorithm assumes 4- or 8- pixel connectivity. Supported types: Byte, Short, Long, Float, Double =item gradient IMAGE [ neighborhood = 8 ] Returns the result or the morphological gradient operator on IMAGE. C determines whether the algorithm assumes 4- or 8- pixel connectivity. Supported types: Byte, Short, Long, Float, Double =item algebraic_difference IMAGE1, IMAGE2 [ inPlace = 0 ] Performs the algebraic difference between IMAGE1 and IMAGE2. Although this is not a morphological operator, it is often used is conjunction with ones. If the boolean flag C is set, IMAGE1 contains the result. Supported types: Byte, Short, Long, Float, Double =item watershed IMAGE [ neighborhood = 4 ] Applies the watershed segmentation to IMAGE with given C. Supported types: Byte =item reconstruct IMAGE1, IMAGE2 [ neighborhood = 8, inPlace = 0 ] Performs morphological reconstruction of IMAGE1 under the mask IMAGE2. Images can be two intensity images or two binary images with the same size. The returned image, is an intensity or binary image, respectively. If boolean C flag is set, IMAGE2 contains the result. C determines whether the algorithm assumes 4- or 8- pixel connectivity. Supported types: Byte, Short, Long, Float, Double =item thinning IMAGE Applies the skeletonization algorithm, returning image with binary object maximal euclidian distance points set. Supported types: Byte =back =cut