How to use Python to convert between MP4 and GIF formats

The principle of converting mp4 to gif is actually very simple, that is, reading the frames of the mp4 file and then merging them into a gif. It can be easily done using the two libraries cv2 and PIL.

import glob

import cv2
from PIL import Image


def convert_mp4_to_jpgs(input_file):
# 先将mp4文件的所有帧读取出保存为图片
video_capture = cv2.VideoCapture(input_file)
still_reading, image = video_capture.read()
frame_count = 0
while still_reading:
cv2.imwrite(f"output/frame_{frame_count:03d}.jpg", image)
# read next image
still_reading, image = video_capture.read()
frame_count += 1


def convert_images_to_gif(output_file):
# 读取目录下图片，用Pillow模块的Image和所有图片合并
# 成一张gif
images = glob.glob(f"output/*.jpg")
images.sort()
frames = [Image.open(image) for image in images]
frame_one = frames[0]
frame_one.save(output_file, format="GIF", append_images=frames[1:],
 save_all=True, duration=40, loop=0)


def convert_mp4_to_gif(input_file, output_file):
convert_mp4_to_jpgs(input_file)
convert_images_to_gif(output_file)


if __name__ == "__main__":
convert_mp4_to_gif("demo.mp4", "output.gif")

After the execution is completed, it is found that the size of the gif file has increased sharply:

You can try to optimize the size of the gif by reducing the number of frames. For example, this video has a total There are 60 frames. If we only take 30 frames, the size will be halved;

frame_one.save(output_file, format="GIF", append_images=[f for i, f in enumerate(frames[1:]) if i % 2 == 0],
 save_all=True, duration=40, loop=0)

The implementation logic is to use the enumerate function to filter even-numbered pictures for synthesis, and the minimum size is compressed from 3.9M to 2M.

After writing this code, I found that there is another awesome library, moviepy, which can be done with just 2 lines of code;

def mp4_to_gif2():
clip = VideoFileClip("demo.mp4")
clip.write_gif("output2.gif")

moviepy has encapsulated the implementation details very simply, and then provided A large number of parameters can be configured by developers themselves. But the file converted using moviepy is 9M. I believe that parameters can be used to optimize and adjust it.

You have to admit that the Python ecosystem is full of libraries. There are all kinds of wheels. There is nothing you can’t do, only things you can’t find.

Of course, you can also convert gifs back to MP4 format. For example, if you see some funny gifs, convert them to mp4 and put them on the short video platform. They might become popular.

def convert_gif_to_mp4():
import moviepy.editor as mp
clip = mp.VideoFileClip("demo.gif")
clip.write_videofile("output.mp4")

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