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tutorial-screencast-to-gif

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Convert screencasts (or other digital movies) into portable animated GIFs using nothing but the command-line

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## Turn a movie into an animated GIF, with just the command-line

![output.gif](https://raw.githubusercontent.com/skepticli/tutorial-screencast-to-gif/master/output.gif)

This is a quickie walkthrough on how to take a `.mov` file (e.g. Apple QuickTime format) and turn it into an animated GIF. But this is more of a walkthrough on __how to use the command-line__ to perform an ostensibly visually-oriented task.

Think of it as [touch typing](http://en.wikipedia.org/wiki/Touch_typing), but for batch digital image manipulation.

Here's the big picture of what we'll do:

1. Make a `.mov` file (e.g. a QuickTime movie)
2. Slice it up into many image files, one for each animation frame.
3. Collect all those image files and stuff them into an animated GIF

A movie's animation is, after all, [just an optical illusion caused by flipping through a bunch of still images](http://en.wikipedia.org/wiki/Film_frame).

Instead of doing this conversion via a clunky point-and-click program or web-app, we'll take this as an opportunity to jump into the __command line__ for more complete, concise control.

### Why...?

A hypothetical use case is:

1. You've created a narrated screencast, such as a tutorial on how to use a web browser.
2. You want to provide an accompanying _write-up_ for people (and search-engines) who prefer to peruse the content of the tutorial, rather than watch the whole thing in a linear sequence. And also, you want your written tutorial to show certain excerpts from your video, without having to re-record those bits specifically.

> Note: I realize the irony of a text-only walkthrough to explain the process of creating a visual explainer, but I'll spiffy the step-by-step at a later date.
>

1. __Why GIFs?__
  In theory, there's no reason why your written tutorial can't be interspersed with mini-video-clips, cut from the main reel. However, GIFs are simply more __portable__ than video. You can paste them into any old webpage and not have to worry if it supports HTML5 playback. It just _works_...because it is such an old technology. Also, for animated-visuals that show a lot of text (such as a screencast on how to use a spreadsheet), GIFs will typically render text more crisply.

2. __Why the command-line?__ 
   The steps in this tutorial are short and simple (and two of them involve just changing directories)...but if you've never used the command-line before, this may seem like a lot more work than just uploading to a web-service [or using Licecap](http://www.cockos.com/licecap/).

Ignoring the specific tradeoffs in using those services, the command-line simply promises more _flexibility_ and _power_ in the medium-to-long term. Being able to create animated GIFs, via the process documented here, is simply a result of combining two very useful programs. So while the command line may be harder to learn, _initially_, it will be by far the best investment in time, if you want to do more aristically/journalistically creative things...at _scale_.

So if you're new to the command-line, don't see this tutorial as a tutorial on how to create animated GIFs. See it as an introduction to the command-line, and to two very powerful image/video manipulation tools that can be tweaked for all varieties and volumes of data-seeking/art-mashup purposes.

### Software pre-requisites

The process detailed here is for UNIX-like operating systems, e.g. Mac OS X and Linux. We'll be using two popular libraries to do the heavy-lifting:

- [FFmpeg](https://www.ffmpeg.org/) - a complete, cross-platform solution to record, convert and stream audio and video.
- [ImageMagick](http://www.imagemagick.org/) - a software suite to create, edit, compose, or convert bitmap images.

You can install these via your system's package manager.

For example, Ubuntu-flavored Linux:

$ apt-get install imagemagick ffmpeg

On Mac OS X, make it easy on yourself [by installing Homebrew](http://brew.sh/). Then run:
    
    $ brew install imagemagick ffmpeg

> Note: This tutorial was tested on: 
> - Mac OS X 10.9.3 (Mavericks)
> - ffmpeg-2.2.4
> - imagemagick-6.8.9-1
>

### Movie-making

You can use pretty much any popular movie-format for this exercise. If you're on a Mac, you'll probably find it easiest to do [create a screencast using the __QuickTime Player__](http://thenextweb.com/apple/2011/01/15/how-to-record-quick-easy-screencast-videos-with-mac-osx/).

Be warned: GIF files can be __massive__. If you run through this exercise on a 10-minute fullscreen video, using the default options (i.e. not downsizing the video or skipping a bunch of frames), you will likely crash your computer. Start with a very small, very short file. Then, as you tinker around with the code, try out bigger files.

For convenience's sake, I've created a short video showing how to create and delete a file via OS X's commandline (yes, exciting, I know). The video file is in the repo. It can also [be downloaded directly via this (temporary) link](//cdn.rawgit.com/dannguyen/screencast-to-gif-tutorial/master/my-screencast.mov).

### Command-line conversion

Here are the quick steps to convert `my-screencast.mov` to `output.gif`. I've inlcuded some steps that satisfy the OCD-file-user in me, by saving temp files in a subdirectory and so forth. I've also inlcuded as few as customization options as possible. This is just a quick and dirty example, you can figure out the tweaks on your own.

#### Step 1. Get with your movie file, via the command-line

Let's go to the directory where `my-screencast.mov` exists via the shell, since that's where we'll be doing most of our work:

OK, so assuming you have a file named `my-screencast.mov` somewhere on your computer, pop open your __shell__ (i.e. the __Terminal.app__ if you're on OSX). Then, `cd` to whatever __directory__ your `my-screencast.mov` file exists.

If you're on a Mac, to make it easy on yourself, just move `my-screencast.mov` (via however you typically move files in your operating system, e.g. __Finder__) into your user __Downloads__ folder.

That way, when you open Terminal, you can just do this:

$ cd ~/Downloads

#### Step 2. Create a sub-directory to work from

Just so we don't have a messy `Downloads` directory, let's make a sub-directory in which we'll do our movie/GIF-making from:

$ mkdir my-test

Copy our movie file into this new subdirectory:

$ cp my-screencast.mov my-test/

Then change to that subdirectory so that we're in same folder as our movie file:

$ cd my-test

#### Step 3. Create another subdirectory for all the still-images

In the conersion process, we'll be generating a ton of new still-image files. Rather than crowd our working space with hundreds/thousands of files, let's just make a subdirectory named `frames` to dump things into:

$ mkdir frames

That's it. **Don't** change into this directory

#### Step 4. Convert a movie into many still-images

We use `ffmpeg` on `my-screencast.mov` to convert `my-screencast.mov` into its many component still-frame image files.

$ ffmpeg -i my-screencast.mov -r 1 frames/image.%05d.png

An explanation of the __flags__ are in order here:

- `-i inputfilename.xyz` &ndash; this specifie the __source__'s filename, e.g the movie file
- `-r [SOME INTEGER]` &ndash; for __frames-per-second__, e.g. 20 fps would result in 20 still-images per-second-of-video. If you leave out the `-r` flag, `ffmpeg` will just use the movie-files frame-rate. 
      
  Example: Another way to think of it: _Decreasing_ the number given to `-r` will _decrease_ the number of image files created, and thus, _decrease_ the size of the final animated GIF.

- The final argument, e.g. `frames/image.%05d.png`, is the _pattern_ that describes the filename for each subsequent image-still (remember, there could be dozens, hundreds, thousads of still-frames from a video).

The file extension could've be `gif`  or `jpg` or any other popular image format. It doesn't matter as the `frames/` subdirectory is just a temporary holding place for the image files, which will all eventually be combined into one big GIF.

If you list the contents of your `frames` subdirectory, you'll see this:

$ ls frames
      image.00001.png image.00036.png
      image.00002.png image.00037.png
      image.00003.png image.00038.png
      image.00004.png image.00039.png

#### Step 5. Combine the still-images into an animated GIF

The __ImageMagick__ library gives us the `convert` [command-line-tool](http://www.imagemagick.org/script/convert.php), which does as it says &ndash; takes an _existing_ image file and turns it into _new_ image file. We can even change the file _format_, e.g. from PNG to GIF, simply by specifying the file extensions in the _existing_ and _new_ filenames:

$ convert existing_image.png new_image.gif

Our specific use-case will look like this:

$ convert frames/image.*.png output.gif

The wildcard operator, `*`, will pluck all files that look like `frames/image.00WHATEVER.png` and feed them into the `convert` program. Lucky for us, `convert` knows that a glob of files can be turned into a single animated GIF.

And we're done! Here's what my `output.gif` looks like:

![output.gif](https://raw.githubusercontent.com/skepticli/tutorial-screencast-to-gif/master/output.gif)

### Custom conversions

There are many ways to tinker with the flags for both `convert` and `ffmpeg` to get the quality and filesize that you want. Now that you've seen how easy it is to run those programs, it's just a matter of reading the (admittedly initimidating) documentation for [ffmpeg](https://ffmpeg.org/ffmpeg.html) and [imagemagick](http://www.imagemagick.org/script/convert.php)

Here's some quick examples of modifications:

##### Add a delay in the GIF animation

The resulting GIF from my screencast is too fast to actually comprehend...this is because I told `ffmpeg` to sample just __one frame per second__, with the flag, `-r 1`:

$ ffmpeg -i my-screencast.mov -r 1 frames/image.%05d.png

The natural tweak would be to increase that number to something like 5 or 10...but that doesn't really add much to the GIF, besides a smoother animation, and the cost is a much, _much_ larger GIF.

So instead, let's tweak how we run `convert`. With `convert`, there is a `delay` flag which specifies the number of _hundreds-of-a-second_ to pause between each frame. So, with the same number of frame-grabs from our 1-fps conversion of the `my-screencast.mov`, let's slow the GIF down by putting a _half a second_ delay between each frame in the GIF:

convert -delay 50 frames/image.*.png output-half-sec-delay.gif

The resulting GIF is the same filesize as in the previous example, except it runs for much longer:

![output-half-sec-delay.gif](https://raw.githubusercontent.com/skepticli/tutorial-screencast-to-gif/master/output-half-sec-delay.gif)

##### Excerpt the video to be animated

`ffmpeg` takes in optional flags to allow us to cut just a piece from the entire video:

$ ffmpeg -i my-screencast.mov -r 20 -ss 00:00:11 -t 00:00:02 frames/image-excerpt.%05d.png

The `-ss` flag specifies where to __start__ the clip. And `-t` specifies the __duration__ of the clip. So in the above example, we'll be cutting a 2-second clip, starting at the __11-second__ mark. Note that I've also switched in `-r 20`, which gets us __20 frames__ per second.

Thus, a 2-second-clip, processed at 20 fps, will create __40__ image files in the `frames/` subdirectory.

And running `convert` (without the `-delay`) results in this GIF:
  
    convert frames/image-excerpt.*.png output-2-sec.gif

Check out the smoother animation:

![output-2sec.gif](https://raw.githubusercontent.com/skepticli/tutorial-screencast-to-gif/master/output-2sec.gif)

##### Change the image color

Boy is my Terminal a drab color. But I really don't want to re-record that video...so, if the _output_ of `ffmpeg` is just a bunch of image files...why don't I just use `convert` to turn those image pixels into a different shade?

Assuming the still-images exist as per the original example (e.g. 1 frame-per-second), let's run `convert`, sans the `delay`, but with the `-negate` flag:

$ convert -negate frames/image.*.png output-inverted.gif

And there we have it:

![output-inverted.gif](https://raw.githubusercontent.com/skepticli/tutorial-screencast-to-gif/master/output-inverted.gif)

---------

You can get pretty far with the command-line, especially with a little piping, to create animated GIFs at an industrial, customized scale (why not make versions with all the color combinations of the rainbow, for starters?).

So that's enough with funky examples for now, even though I think it'd be fun to demonstrate how to dynamically-delaye and resize frames (e.g. to "pause" or "zoom", even if the original screencast didn't have such transitions). Sure, you're probably thinking, well, _I can do that in Final Cut, like an adult_...but that misses the point of how fun it is to solve problems with a little logic and without carpal-tunnel-causing-mouse-clicking. And also, without having to pay for Final Cut.

(Though realistically, even if you're _good_ at command-line scripting, I recommend doing wrapping these compllicated scripts in nice Ruby/Python/Perl wrapper, to avoid situations where [you accidentally wipe out your hard drive](http://thenextweb.com/media/2012/05/21/how-pixars-toy-story-2-was-deleted-twice-once-by-technology-and-again-for-its-own-good/) because of a misplaced quote-mark)

Making animated-GIFs is a fun venture. But again, keep your mind open to the potential non-GIF related uses for `ffmpeg` and `convert`. For example, I like converting the output of `ffmpeg` with [Tesseract](https://code.google.com/p/tesseract-ocr/), the command-line optical-character-recognition program, for cases when video clips shots of (legible) documents. Getting comfortable with the command-line allows for limitless custom applications.

I've got some ideas for fun additions to this already convuluted tutorial. For now, here are some other resources:

- [How to record quick, easy screencast videos with Mac OSX](http://thenextweb.com/apple/2011/01/15/how-to-record-quick-easy-screencast-videos-with-mac-osx/)
- [How do I convert a video to GIF using ffmpeg, with reasonable quality?](http://superuser.com/questions/556029/how-do-i-convert-a-video-to-gif-using-ffmpeg-with-reasonable-quality)
- [Making Animated GIFs from the Linux Command Line](http://www.leshylabs.com/blog/dev/2013-08-04-Making_Animated_GIFs_from_the_Linux_Command_Line.html) - in this article, the author refers to a Perl-wrapper he uses to conveniently contain all the shell commands in one file.

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