animate

helper script to combine images together into an animation with ffmpeg

output.mp4

Install

You need a recent version of the rust compiler. Install instructions can be found here

cargo install --git https://github.com/fluid-Dynamics-Group/animate --force

You must also have ffmpeg in your $PATH. It can be installed on debian based systems with:

sudo apt install ffmpeg

Usage

Say you have a folder that contains a bunch of files that you want to animate together. They are distinguished by a zero-padded index of the file. animate is a handy cli tool to parse the correct input arguments to ffmpeg to animate the files together into a single output video:

static
├── plot_anim_00001.png
├── plot_anim_00002.png
├── plot_anim_00003.png
├── plot_anim_00004.png
├── plot_anim_00005.png
├── plot_anim_00006.png
├── plot_anim_00007.png
├── plot_anim_00008.png
├── plot_anim_00009.png
├── plot_anim_00010.png
├── plot_anim_00011.png
├── plot_anim_00012.png
...

Animate all the files in a folder together

in the above case, you could animate all the files in the child folder ./static at 30 fps into output.mp4 with this command:

animate 30 ./output.mp4 folder ./static

be caseful, though. This command expects that only files matching the general pattern will be present. If your folder contains

static
├── plot_anim_00001.png
├── plot_anim_00002.png
├── plot_anim_00003.png
├── plot_anim_00004.png
├── another_file.txt
├── plot_anim_00005.png
├── plot_anim_00006.png

this command will fail to run, since it cannot find a parsing method that works for all files.

Animate all files matching a pattern

to handle the presence of additional files in a directory (such as the above ./another_file.txt you can instead use xargs on linux to pass in a list of all files you wish to parse.

animate 30 ./output.mp4 pattern ./static/plot_anim_*.png

if run from a unix shell, this will animate all the plot_anim_xxxxx.png files together into ./output.mp4 at 30 fps. Note that the list of files passed in must all belong to the same base directory, so the following will not work:

animate 30 ./output.mp4 pattern ./static/plot_anim_*.png ./another_dir/plot_anim_*.png

CLI Information

$ animate --help

Animate pictures together into videos with ffmpeg

Usage: animate [OPTIONS] <FRAMERATE> <OUTPUT_PATH> <COMMAND>

Commands:
  folder   animate all files in a folder together
  pattern  animate a list of files (usually generated by xargs) together
  help     Print this message or the help of the given subcommand(s)

Arguments:
  <FRAMERATE>
  <OUTPUT_PATH>

Options:
  -v, --verbose  print output of ffmpeg
  -h, --help     Print help information
  -V, --version  Print version information

Saving data with zero padding

Since this utility only work with zero-padded file names, its worthwhile to mention how to generate these filenames

Python

instead of generating a file name like this:

import matplotlib.pyplot as plt
for i in range(100):
	name = f"file_name{i}.png"
	plt.savefig(name)

do:

name = f"file_name{i:05}.png"

This way, loop iteration i=1 gets exported as file_name00001.png

Julia

There are two ways to zero pad in julia:

instead of

for i in 1:100
	name = "file_name_" * string(i) * ".png"
end

do:

name = "file_name_" * lpad(i, 5, "0") * ".png"

or:

using Printf
name = @sprintf "file_name_%05i.png" i

which will generate a file name file_name_00001.png.