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Re: Recursive image processing (with ImageMagic)

by Kenosis (Priest)
on Nov 23, 2012 at 03:11 UTC ( #1005204=note: print w/replies, xml ) Need Help??

in reply to Recursive image processing (with ImageMagic)

I have a vested interest in your question as I have a B&W photography background, and frequently convert color images to grayscale (I'm not British... :). Given this, perhaps the following will assist you--at least to start:

use strict; use warnings; use File::Find::Rule; use File::Basename; use File::Path qw/mkpath/; use List::Util qw/sum/; use GD; my $sourceDir = 'A'; my $destinDir = 'B'; -d $sourceDir or die 'Error: Source directory does not exist.'; !-d $destinDir or die 'Error: Destination directory already exists.'; my @files = File::Find::Rule->file()->name(qr/\.png$/i)->in($sourceDir +) or die 'No png files found in source directory.'; print "\nNumber of png files to convert to grayscale: ", scalar @files +, "\n\n"; for my $pngFile (@files) { my $destinPath = $pngFile =~ s{^$sourceDir(?=/)}{$destinDir}r; my $dir = dirname($destinPath); if ( !-d $dir ) { mkpath( $dir, { error => \my $err } ); !@$err or die qq{Unable to create directory "$dir"}; } print "Processing: $pngFile"; my $image = GD::Image->new($pngFile); for my $i ( 0 .. $image->colorsTotal() - 1 ) { my @gray = ( ( sum $image->rgb($i) ) / 3 ) x 3; $image->colorDeallocate($i); $image->colorAllocate(@gray); } open my $fh, '>', $destinPath or die $!; binmode $fh; print $fh $image->png; close $fh; print " - Done!\n"; } print "\nJob completed.\n";

Sample output when running:

Number of png files to convert to grayscale: 6 Processing: A/adelaide-rosella.png - Done! Processing: A/frog.png - Done! Processing: A/C/chicken_profile.png - Done! Processing: A/C/tux.png - Done! Processing: A/C/D/crowned_crane.png - Done! Processing: A/C/D/cuckoo.png - Done! Job completed.

There's likely a more efficient way to do this, but it worked well in my tests--although I'm not processing millions of images. You'll notice that I used GD for the actual image processing. If you're keen on using ImageMagick, you could just modify this script for it.

It will preserve the structure of the source directory, mirroring it in the destination directory, and convert all found png files to grayscale, and then write them into their destination directory. There's an initial check for the destination directory already existing, since files might otherwise be overwritten.

Hope this helps!

Replies are listed 'Best First'.
Re^2: Recursive image processing (with ImageMagic)
by wvick (Novice) on Nov 23, 2012 at 17:37 UTC
    This looks almost like "job done"! Thank you very much, Kenosis!

      You're most welcome, wvick!

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[moritz]: seems there's a size limit for hostenum, and the error message just sucks
[vrk]: None, other than the location of the error: auto/NetAddr/IP/
[vrk]: Aha, there's a reference to "bug report 82719" in NetAddr/'s sub _splitref.
[moritz]: wow, that's their idea of an "improved error message"
[moritz]: how about "This network is too large to enumerate all host addresses." or so?
[vrk]: Well, there's a call to notcontiguous() before the error, whose description is "counts the bit positions remaining in the mask when the rightmost '0's are removed"
[vrk]: Clear as mud!

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