Tool to find images named prefix_NN_postfix.png and convert them to APNGs

animate_pngs.py

import os, re, glob
import numpy as np
from PIL import Image, ImageChops
from collections import defaultdict

# Finds sequences of images with common name part+_<frame#>_etc.png 
# and merges them into a single animated PNG.

INITIAL_SPEED = 20
TYPE2 = True
IMAGE_FOLDER = '.'

def calculate_difference2(frame1, frame2):
    """Calculate the visual difference between two images.  """
    diff = ImageChops.difference(frame1.convert('L'), frame2.convert('L'))
    total_difference = np.sum(np.array(diff))
    return total_difference / (frame1.size[0] * frame1.size[1] * 255)

def calculate_difference1(frame1, frame2):
    """Calculate the visual difference between two images.  """
    mse = np.mean((np.array(frame1.convert('L')) - np.array(frame2.convert('L'))) ** 2)
    return int(100 / (1 + mse))
  
calculate_difference = calculate_difference2 if TYPE2 else calculate_difference1

def create_animation(images, output_filename, speed=100, use_difference=False):
    """Create a APNG from a list of PIL Image objects. """
    if use_difference and len(images) > 1:
        frame_delays = [calculate_difference(images[i], images[i+1]) for i in range(len(images)-1)]
        max_diff = max(frame_delays, default=1)
        frame_delays = [(1 - (diff / max_diff)) * speed for diff in frame_delays]
        frame_delays.append(frame_delays[-1])
    else:
        frame_delays = [speed] * len(images)

    frame_delays = [int(delay) for delay in frame_delays]
    images[0].save(output_filename, save_all=True, append_images=images[1:], duration=frame_delays, loop=0)

def detect_and_process_sequences(image_folder, speed=100, use_difference=False):
    """Detect common prefixes in filenames, indicating sequences, and animate each sequence."""
    files = glob.glob(f'{image_folder}\\**\\*.png', recursive=True)
    prefix_pattern = re.compile(r'^(.+)_\d+.*?\.png$')
    sequences = defaultdict(list)

    for file in files:
        match = prefix_pattern.match(file)
        if match:
            prefix = match.group(1)
            sequences[prefix].append(file)

    for prefix, files in sequences.items():
        # Sort files by frame number
        files.sort(key=lambda x: int(re.search(r'.+_(\d+).*?\.png$', x).group(1)))
        images = [Image.open(os.path.join(image_folder, f)) for f in files]
        output_filename = f"{prefix}.apng"
        print(f"Creating {output_filename}... ", end='')
        create_animation(images, output_filename, speed=speed, use_difference=use_difference)
        print(f"OK")
        out_name_new = output_filename.replace('.apng', '.png')
        i = 1
        while os.path.isfile(out_name_new):
            out_name_new = re.sub(r' _\(\d+\)\.png', '.png', out_name_new)
            out_name_new = out_name_new.replace('.png', f'_({i}).png')
            i+=1
        os.rename(output_filename,  out_name_new)

detect_and_process_sequences(IMAGE_FOLDER, speed=INITIAL_SPEED, use_difference=False)