ImageRGB(B)    User Contributed Perl Documentation    ImageRGB(B)



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:

       o color space conversion
       o common image filters
       o 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(f)).

       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@auck-
       land.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 COPY-
       ING in the PDL distribution. If this file is separated
       from the PDL distribution, the copyright notice should be
       included in the file.



perl v5.6.1                 2002-04-08                ImageRGB(B)