Math::Gradient - Perl extension for calculating gradients for
colour transitions, etc.
use Math::Gradient qw(multi_gradient);
# make a 100-point colour palette to smothly transition between 6
RGB values
my(@hot_spots) = ([ 0, 255, 0 ], [ 255, 255, 0 ], [ 127, 127, 127
], [ 0, 0, 255 ], [ 127, 0, 0 ], [ 255, 255, 255 ]);
my(@gradient) = multi_array_gradient(100,
@hot_spots);
Math::Gradient is used to calculate smooth transitions between
numerical values (also known as a "Gradient"). 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.
- gradient($start_value,
$end_value, $steps)
- This function will return an array of evenly distributed values between
$start_value and
$end_value. All three values supplied should be
numeric. $steps should be the number of steps that
should occur between the two points; for instance, gradient(0, 10, 4)
would return the array (2, 4, 6, 8); the 4 evenly-distributed steps
necessary to get from 0 to 10, whereas gradient(0, 1, 3) would return
(0.25, 0.5, 0.75). This is the basest function in the Math::Gradient
module and isn't very exciting, but all of the other functions below
derive their work from it.
- array_gradient($start_value,
$end_value, $steps)
- While gradient() takes numeric values for
$start_value and
$end_value, array_gradient() 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. array_gradient() will return a list of arrayrefs
signifying the gradient of all values on the lists
$start_value and
$end_value.
For example, calling array_gradient([ 0, 100, 2 ], [ 100, 50,
70], 3) would return: ([ 25, 87.5, 19 ], [ 50, 75, 36 ], [ 75, 62.5, 53
]).
- multi_gradient($steps,
@values)
- multi_gradient() 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
$steps is less than the number of entries in the
list @values, items are deleted from
@values instead.
For example, calling multi_gradient(10, 0, 100, 50) would
return: (0, 25, 50, 75, 100, 90, 80, 70, 60, 50)
- multi_array_gradient($steps,
@values)
- multi_array_gradient() is the same as multi_gradient, except that
it works on arrayrefs instead of scalars (like array_gradient() is
to gradient()).
Tyler MacDonald, <japh@crackerjack.net>
Copyright 2003 by Tyler MacDonald
This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.