#!/usr/bin/perl -w

use Gimp;
use Gimp::Fu;
use PDL::LiteF;
use strict;
use warnings;
#BEGIN { $Gimp::verbose = 3; }

# convert to greyscale. could be improved, but should still be fast!
sub togrey {
   my $pdl = shift;
   $pdl->convert(ushort);
   $pdl=$pdl->inner(pdl[54,183,18])/256;
   $pdl->convert(byte);
   $pdl;
}

podregister {
   Gimp->progress_init ("Mapping to '$gradient'", -1);

   my $grad = pdl byte, map $_*255, Gimp->gradient_get_uniform_samples($gradient,256,0);
   $grad->reshape(4,256);

   my $alpha = $drawable->has_alpha;

   $grad = $grad->slice('0:-2') unless $alpha;
   $grad = togrey($grad)->dummy(0) unless $drawable->is_rgb;

   my $depth = ($grad->dims)[0]; # precalculate
   $grad = $grad->xchg(0,1); # this form is later needed in index, so do it now

   my @bounds = $drawable->bounds;
   {
      my $src = new Gimp::PixelRgn ($drawable,@bounds,0,0);
      my $dst = new Gimp::PixelRgn ($drawable,@bounds,1,1);

      my $iter = Gimp->pixel_rgns_register($src,$dst);
      my $area = $bounds[2]*$bounds[3];
      my $progress = 0;

      do {
         my $data = $src->data;
         $data = $data->slice("0:-2") if $alpha; # get rid of alpha
         $data = $src->bpp > 2 ? togrey($data) : $data->clump(2);

         # now map from grey values to gradient
         $dst->data( index($grad,$data->dummy(0,$depth)) );

         $progress += ($src->w*$src->h)/$area;
         Gimp->progress_update ($progress);
      } while (Gimp->pixel_rgns_process ($iter));
   }
   Gimp->progress_update (1);
   $drawable->merge_shadow (1);
   $drawable->update (@bounds);
   ();
};

exit main;
__END__

=head1 NAME

map_to_gradient - Map grayscale values to gradient

=head1 SYNOPSIS

<Image>/Filters/Colors/Map/Map To Gradient...

=head1 DESCRIPTION

Map all the pixels to the colours of a gradient according to their
greyscale value.

=head1 PARAMETERS

  [PF_GRADIENT, "gradient", "The gradient to map to", 'FG to BG (RGB)'],

=head1 IMAGE TYPES

RGB*, GRAY

=head1 AUTHOR

Marc Lehmann <pcg@goof.com>

=head1 DATE

19990802

=head1 LICENSE

Distributed under the same terms as Gimp-Perl.