frame_align.py

import math
from decimal import Decimal


def FindOptimalRepetitions(gif1Duration, gif2Duration, maxStretch, maxRepetitions) -> dict:
    searchResults = []

    for i in range(maxRepetitions):
        gif1Repetitions = i + 1
        gif2Repetitions = round(gif1Duration * gif1Repetitions / gif2Duration)

        difference = float((Decimal(str(gif2Duration)) * Decimal(str(gif2Repetitions))) /
                           (Decimal(str(gif1Duration)) * Decimal(str(gif1Repetitions))))

        searchResults.append(
            {
                "gif1reps": gif1Repetitions,
                "gif2reps": gif2Repetitions,
                "difference": difference,
            }
        )

        if abs(difference - 1) < maxStretch:
            break

    sortedSearchResults = sorted(
        searchResults, key=lambda item: abs(item["difference"] - 1))

    return sortedSearchResults[0]


def FindOptimalAnimationSettings(animation1, animation2):
    return max(animation1.frames * animation1.repetitions, animation2.frames * animation2.repetitions), max(animation1.framerate, animation2.framerate)


class Animation:
    def __init__(self, frames, framerate, repetitions=0) -> None:
        self.frames = frames
        self.framerate = framerate
        self.repetitions = repetitions

    def Duration(self):
        return self.frames / self.framerate

    def RepetitionFrames(self):
        return self.frames * self.repetitions

    def SampleFrameAtTime(self, sampleTime):
        framerateAdjustedSampleTime = sampleTime * self.framerate

        sampledFrame = math.floor(
            framerateAdjustedSampleTime) % self.frames
        return sampledFrame


def AlignFrames(Animation1, Animation2, maxStretch, maxRepetitons) -> dict:

    optimalRepetitions = FindOptimalRepetitions(
        Animation1.Duration(), Animation2.Duration(), maxStretch, maxRepetitons)

    Animation1Loop = Animation(
        Animation1.frames,
        Animation1.framerate,
        repetitions=optimalRepetitions["gif1reps"])

    Animation2Loop = Animation(
        Animation2.frames,
        Animation2.framerate * optimalRepetitions["difference"],
        repetitions=optimalRepetitions["gif2reps"])

    optimalFrames, optimalSamplerate = FindOptimalAnimationSettings(
        Animation1Loop, Animation2Loop)

    frames = []

    for frame in range(optimalFrames):
        time = frame / optimalSamplerate

        frames.append((Animation1Loop.SampleFrameAtTime(time),
                       Animation2Loop.SampleFrameAtTime(time)))

    return {"frames": frames,
            "framerate": optimalSamplerate}