# vim: set et sw=4 sts=4 fileencoding=utf-8:
#
# Alternative API for the Sense HAT
# Copyright (c) 2016-2018 Dave Jones <dave@waveform.org.uk>
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# * Neither the name of the copyright holder nor the
# names of its contributors may be used to endorse or promote products
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#
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"""
Defines various easing functions for the screen animation methods.
"""
from __future__ import (
unicode_literals,
absolute_import,
print_function,
division,
)
[docs]def linear(steps):
"""
Linear easing function; yields *steps* values between 0.0 and 1.0.
.. image:: images/linear.*
:align: center
This is the default easing function which simply progresses the animation
at a constant rate from start to finish.
"""
if steps <= 0:
raise ValueError('steps must be a positive integer >0')
elif steps == 1:
yield 1.0
else:
for t in range(steps):
yield t / (steps - 1)
[docs]def ease_in(steps):
"""
Quadratic ease-in function; yields *steps* values between 0.0 and 1.0.
.. image:: images/ease_in.*
:align: center
This function starts the animation off slowly, and builds speed as it
progresses, finishing abruptly.
"""
for t in linear(steps):
yield t ** 2
[docs]def ease_out(steps):
"""
Quadratic ease-out function; yields *steps* values between 0.0 and 1.0.
.. image:: images/ease_out.*
:align: center
This function starts the animation suddenly and then eases it gradually
to a halt.
"""
for t in linear(steps):
yield t * (2 - t)
[docs]def ease_in_out(steps):
"""
Quadratic ease-in-out function; yields *steps* values between 0.0 and 1.0.
.. image:: images/ease_in_out.*
:align: center
This function starts the animation gradually, progresses rapidly at the
mid-point, and eases gently to a halt.
"""
for t in linear(steps):
yield 2 * t ** 2 if t < 0.5 else (4 - 2 * t) * t - 1