This post is a bit of a little note to myself: The other day, when writing a post on the new installer for the CEA, I wanted to stitch together a bunch of screenshots into a GIF, with each screenshot showing for one second.

Using ffmpeg to create a GIF from screenshots

I used the portable version of ShareX to create the screenshots. It turns out, ShareX also ships ffmpeg.exe. According to the website](https://ffmpeg.org/), ffmpeg is

A complete, cross-platform solution to record, convert and stream audio and video.

And of course, ffmpeg.exe has a million options. The one I ended up using was this:

ffmpeg -framerate 1 -i screenshots-%04d.png -i palette.png -lavfi paletteuse -y screenshots.gif

Let’s break it down:

• -framerate 1: duh. 1 second per frame
• -i screenshots-%04d.png: instruct ffmpeg to use files matching screenshots-%04d.png (in the current working directory) as input. The %04d portion means an integer decimal number, four digits long, padded with leading zeros. So save the screenshots as screenshots-0001.png, screenshots-0002.png etc.
• -i palette.png: use this file as a “palette”, since the GIF will end up with 256 colors and you want to make sure the palette used by the GIF includes all the colors in your screenshots.
• -lavfi paletteuse: I’m not totally sure. I think this makes the palette be used. Let’s just assume a magic invocation.
• -y: Overwrite output files (this isn’t strictly necessary)
• screenshots.gif: This is the name of the GIF file to produce.

Where did palette.png come from?! I created it with ffmepg.exe:

ffmpeg -i screenshots-%04d.png screenshots.gif -vf palettegen -y palette.png

The important part here is the -vf palettegen and the output file name palette.png. Run this first.

Using ffmpeg to create screenshots from a GIF

ShareX also has the capability to record a GIF instead of taking just a snapshot. I think using this feature is required to download the ffmpeg.exe file - it will show up in a subfolder ShareX/Tools below your portable installation of ShareX.

You can “explode” a GIF into it’s frames with this command:

ffmepg -i mygif.gif -vsync 0 mypngs-%04d.png

This time the input file is the GIF and the output file is specified using the wildcard %04d since we are creating a bunch of PNG files.

The -vsync 0 parameter is something I found on the internet. I’m assuming it’s required to make sure each frame ends up as it’s own PNG file, as per the documentation of the -vsync parameter for 0:

Each frame is passed with its timestamp from the demuxer to the muxer.

Now you can edit each frame, re-arrange them, delete some, add in new ones - Just be sure to re-index them in increasing order (mypngs-0001.png, mypngs-0002.png, mypngs-0003.png etc.). A bit of python scripting can help with that. Something like:

import os
fnames = sorted([f for f in os.listdir('.') if f.startswith('mypngs-')])
for i, fname in enumerate(fnames):
    os.rename(fname, 'mypngs-%04d.png' % i))

Then, you can use the method above, to re-create the GIF. You might need to play around with the -framerate parameter.