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.\"
.IX Title "Gradient 3pm"
.TH Gradient 3pm "2010-03-12" "perl v5.10.1" "User Contributed Perl Documentation"
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.SH "NAME"
Math::Gradient \- Perl extension for calculating gradients for colour transitions, etc.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
use Math::Gradient qw(multi_gradient);
.PP
# make a 100\-point colour palette to smothly transition between 6 \s-1RGB\s0 values
.PP
my(@hot_spots) = ([ 0, 255, 0 ], [ 255, 255, 0 ], [ 127, 127, 127 ], [ 0, 0, 255 ], [ 127, 0, 0 ], [ 255, 255, 255 ]);
.PP
my(@gradient) = multi_array_gradient(100, \f(CW@hot_spots\fR);
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Math::Gradient is used to calculate smooth transitions between numerical values (also known as a \*(L"Gradient\*(R"). I wrote this module mainly to mix colours, but it probably has several other applications. Methods are supported to handle both basic and multiple-point gradients, both with scalars and arrays.
.SH "FUNCTIONS"
.IX Header "FUNCTIONS"
.ie n .IP "gradient($start_value, $end_value, $steps)" 4
.el .IP "gradient($start_value, \f(CW$end_value\fR, \f(CW$steps\fR)" 4
.IX Item "gradient($start_value, $end_value, $steps)"
This function will return an array of evenly distributed values between \f(CW$start_value\fR and \f(CW$end_value\fR. All three values supplied should be numeric. \f(CW$steps\fR should be the number of steps that should occur  between the two points; for instance, gradient(0, 10, 4) would return the array (2, 4, 6, 8); the 4 evenly-distributed steps necessary to get from 0 to 10, whereas gradient(0, 1, 3) would return (0.25, 0.5, 0.75). This is the basest function in the Math::Gradient module and isn't very exciting, but all of the other functions below derive their work from it.
.ie n .IP "array_gradient($start_value, $end_value, $steps)" 4
.el .IP "array_gradient($start_value, \f(CW$end_value\fR, \f(CW$steps\fR)" 4
.IX Item "array_gradient($start_value, $end_value, $steps)"
While \fIgradient()\fR takes numeric values for \f(CW$start_value\fR and \f(CW$end_value\fR, \fIarray_gradient()\fR takes arrayrefs instead. The arrays supplied are expected to be lists of numerical values, and all of the arrays should contain the same number of elements. \fIarray_gradient()\fR will return a list of arrayrefs signifying the gradient of all values on the lists \f(CW$start_value\fR and \f(CW$end_value\fR.
.Sp
For example, calling array_gradient([ 0, 100, 2 ], [ 100, 50, 70], 3) would return: ([ 25, 87.5, 19 ], [ 50, 75, 36 ], [ 75, 62.5, 53 ]).
.ie n .IP "multi_gradient($steps, @values)" 4
.el .IP "multi_gradient($steps, \f(CW@values\fR)" 4
.IX Item "multi_gradient($steps, @values)"
\&\fImulti_gradient()\fR calculates multiple gradients at once, returning one list that is an even transition between all points, with the values supplied interpolated evenly within the list. If \f(CW$steps\fR is less than the number of entries in the list \f(CW@values\fR, items are deleted from \f(CW@values\fR instead.
.Sp
For example, calling multi_gradient(10, 0, 100, 50) would return: (0, 25, 50, 75, 100, 90, 80, 70, 60, 50)
.ie n .IP "multi_array_gradient($steps, @values)" 4
.el .IP "multi_array_gradient($steps, \f(CW@values\fR)" 4
.IX Item "multi_array_gradient($steps, @values)"
\&\fImulti_array_gradient()\fR is the same as multi_gradient, except that it works on arrayrefs instead of scalars (like \fIarray_gradient()\fR is to \fIgradient()\fR).
.SH "AUTHOR"
.IX Header "AUTHOR"
Tyler MacDonald, <japh@crackerjack.net>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2003 by Tyler MacDonald
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.