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.IX Title "ImageRGB 3pm"
.TH ImageRGB 3pm "2023-06-17" "perl v5.36.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
PDL::ImageRGB \-\- some utility functions for RGB image data handling
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Collection of a few commonly used routines involved in handling of \s-1RGB,\s0 palette
and grayscale images. Not much more than a start. Should be a good place to
exercise some of the broadcast/map/clump \s-1PP\s0 stuff.
.PP
Other stuff that should/could go here:
.IP "\(bu" 3
color space conversion
.IP "\(bu" 3
common image filters
.IP "\(bu" 3
image rebinning
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& use PDL::ImageRGB;
.Ve
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.SS "cquant"
.IX Subsection "cquant"
quantize and reduce colours in 8\-bit images
.PP
.Vb 1
\&    ($out, $lut) = cquant($image [,$ncols]);
.Ve
.PP
This function does color reduction for <=8bit displays and accepts 8bit \s-1RGB\s0
and 8bit palette images. It does this through an interface to the ppm_quant
routine from the pbmplus package that implements the median cut routine which
intellegently selects the 'best' colors to represent your image on a <= 8bit
display (based on the median cut algorithm). Optional args: \f(CW$ncols\fR 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).
.PP
Returns a list containing the new palette image (type PDL_Byte) and the \s-1RGB\s0
colormap.
.SS "interlrgb"
.IX Subsection "interlrgb"
Make an \s-1RGB\s0 image from a palette image and its lookup table.
.PP
.Vb 1
\&    $rgb = $palette_im\->interlrgb($lut)
.Ve
.PP
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 \f(CW$lut\fR ndarray (you can do that by saying
\&\f(CW$lut\fR\->\fBset_dataflow_f\fR\|(1)).
.SS "rgbtogr"
.IX Subsection "rgbtogr"
Converts an \s-1RGB\s0 image to a grey scale using standard transform
.PP
.Vb 1
\&   $gr = $rgb\->rgbtogr
.Ve
.PP
Performs a conversion of an \s-1RGB\s0 input image (3,x,....) to a
greyscale image (x,.....) using standard formula:
.PP
.Vb 1
\&   Grey = 0.301 R + 0.586 G + 0.113 B
.Ve
.SS "bytescl"
.IX Subsection "bytescl"
Scales a pdl into a specified data range (default 0\-255)
.PP
.Vb 1
\&        $scale = $im\->bytescl([$top])
.Ve
.PP
By default \f(CW$top\fR=255, otherwise you have to give the desired top value as an
argument to \f(CW\*(C`bytescl\*(C'\fR. Normally \f(CW\*(C`bytescl\*(C'\fR doesn't rescale data that fits
already in the bounds 0..$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 \f(CW$top\fR and
the min at 0 you give a negative \f(CW$top\fR value to indicate this.
.SH "BUGS"
.IX Header "BUGS"
This package doesn't yet contain enough useful functions!
.SH "AUTHOR"
.IX Header "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 \s-1COPYING\s0 in the \s-1PDL\s0
distribution. If this file is separated from the \s-1PDL\s0 distribution,
the copyright notice should be included in the file.