Try setting the depth of the new image to 8 (it defaults to 16) 
$opimage->Set(magick=>'RGB', depth=>8);

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You can get the depth of the original image like this: 
my $depth = $ipimage->Get('depth');

[download]

In reply to Re: ImageMagick - why do these snippets act differently? by tangent
in thread ImageMagick - why do these snippets act differently? by pete_l

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