generated from thinkode/modelRepository
84 lines
2.3 KiB
Python
84 lines
2.3 KiB
Python
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from dataclasses import dataclass
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from moviepy.Effect import Effect
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@dataclass
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class AccelDecel(Effect):
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"""Accelerates and decelerates a clip, useful for GIF making.
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Parameters
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----------
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new_duration : float
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Duration for the new transformed clip. If None, will be that of the
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current clip.
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abruptness : float
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Slope shape in the acceleration-deceleration function. It will depend
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on the value of the parameter:
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* ``-1 < abruptness < 0``: speed up, down, up.
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* ``abruptness == 0``: no effect.
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* ``abruptness > 0``: speed down, up, down.
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soonness : float
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For positive abruptness, determines how soon the transformation occurs.
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Should be a positive number.
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Raises
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------
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ValueError
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When ``sooness`` argument is lower than 0.
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Examples
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--------
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The following graphs show functions generated by different combinations
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of arguments, where the value of the slopes represents the speed of the
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videos generated, being the linear function (in red) a combination that
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does not produce any transformation.
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.. image:: /_static/medias/accel_decel-fx-params.png
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:alt: acced_decel FX parameters combinations
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"""
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new_duration: float = None
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abruptness: float = 1.0
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soonness: float = 1.0
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def _f_accel_decel(
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self, t, old_duration, new_duration, abruptness=1.0, soonness=1.0
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):
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a = 1.0 + abruptness
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def _f(t):
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def f1(t):
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return (0.5) ** (1 - a) * (t**a)
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def f2(t):
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return 1 - f1(1 - t)
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return (t < 0.5) * f1(t) + (t >= 0.5) * f2(t)
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return old_duration * _f((t / new_duration) ** soonness)
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def apply(self, clip):
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"""Apply the effect to the clip."""
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if self.new_duration is None:
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self.new_duration = clip.duration
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if self.soonness < 0:
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raise ValueError("'sooness' should be a positive number")
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return clip.time_transform(
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lambda t: self._f_accel_decel(
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t=t,
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old_duration=clip.duration,
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new_duration=self.new_duration,
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abruptness=self.abruptness,
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soonness=self.soonness,
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)
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).with_duration(self.new_duration)
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