A comment on this script was made to me thru email, and so I'll post it here in case in may help someone looking at this snippet.

edada wrote:

Hi, I had some problems changing brightness with Imager using your code : 

my @redmap = map {  int( $r * $_)  } 0..255;
my @greenmap = map {  int( $g * $_)  } 0..255;
my @bluemap = map {  int( $b * $_)  } 0..255;
[..]
 $newimg->map( red=>\@redmap, green=>\@greenmap, blue=>\@bluemap );

 $newimg->filter(type=>'contrast', intensity=> $c);

[download]
In Imager::Filters doc I can read that the contrast filter "scales each channel by intensity. Values of intensity < 1 will reduce the contrast". Your map do the same if $r => $b => $g ! It's supposed to change brightness and not contrast. I simply recommand you writing it with a : 
my @redmap = map {  int( $r + $_)  } 0..255;

[download]
and using null value as default value.
I'm not really a human, but I play one on earth. flash japh

In reply to Re: batch rgb brightness and contrast adjustment by zentara
in thread batch rgb brightness and contrast adjustment by zentara

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