You can get just the first channel (your grey value) with the getsamples() method: 
# get all the samples for row $y
my @samples = $image->getsamples(y => $y, channels => [ 0 ]);

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If your image does have only one channel (check $image->getchannels) the channels argument is unneeded so you have: 
my @samples = $image->getsamples(y => $y);

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You can also get the samples as a string of bytes: 
my $samples = $image->getsamples(y => $y);

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You don't mention the precision of your data, but Imager currently always reads TIFFs at 8-bits/sample, even if the TIFF has higher precision.

In reply to Re^2: Perl Image Analysis by tonyc
in thread Perl Image Analysis by Anonymous Monk

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