NAME

       PDL::ImageRGB -- some utility functions for RGB image data handling

DESCRIPTION

       Collection of a few commonly used routines involved in handling of RGB, palette and grayscale images. Not
       much more than a start. Should be a good place to exercise some of the thread/map/clump PP stuff.

       Other stuff that should/could go here:

       •  color space conversion

       •  common image filters

       •  image rebinning

SYNOPSIS

        use PDL::ImageRGB;

FUNCTIONS

   cquant
       quantize and reduce colours in 8-bit images

           ($out, $lut) = cquant($image [,$ncols]);

       This  function  does color reduction for <=8bit displays and accepts 8bit RGB and 8bit palette images. It
       does this through an interface to the ppm_quant routine from the  pbmplus  package  that  implements  the
       median  cut  routine  which  intellegently selects the 'best' colors to represent your image on a <= 8bit
       display (based on the median cut algorithm). Optional args: $ncols sets the maximum  nunmber  of  colours
       used  for  the output image (defaults to 256).  There are images where a different color reduction scheme
       gives better results (it seems this is true for images containing large areas with very smoothly changing
       colours).

       Returns a list containing the new palette image (type PDL_Byte) and the RGB colormap.

   interlrgb
       Make an RGB image from a palette image and its lookup table.

           $rgb = $palette_im->interlrgb($lut)

       Input should be of an integer type and the lookup table  (3,x,...).  Will  perform  the  lookup  for  any
       N-dimensional  input pdl (i.e. 0D, 1D, 2D, ...). Uses the index command but will not dataflow by default.
       If you want it to dataflow the dataflow_forward flag must be set in the $lut piddle (you can do  that  by
       saying $lut->set_dataflow_f(1)).

   rgbtogr
       Converts an RGB image to a grey scale using standard transform

          $gr = $rgb->rgbtogr

       Performs  a  conversion  of  an  RGB input image (3,x,....) to a greyscale image (x,.....) using standard
       formula:

          Grey = 0.301 R + 0.586 G + 0.113 B

   bytescl
       Scales a pdl into a specified data range (default 0-255)

               $scale = $im->bytescl([$top])

       By default $top=255, otherwise you have to give the desired  top  value  as  an  argument  to  "bytescl".
       Normally  "bytescl"  doesn't  rescale data that fits already in the bounds 0..$top (it only does the type
       conversion if required).  If you want to force it to rescale so that the max of the output is at $top and
       the min at 0 you give a negative $top value to indicate this.

BUGS

       This package doesn't yet contain enough useful functions!

AUTHOR

       Copyright 1997 Christian Soeller <c.soeller@auckland.ac.nz> All rights reserved. There  is  no  warranty.
       You  are allowed to redistribute this software / documentation under certain conditions. For details, see
       the file COPYING in the PDL distribution. If this file  is  separated  from  the  PDL  distribution,  the
       copyright notice should be included in the file.

perl v5.26.0                                       2017-08-06                                      ImageRGB(3pm)