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+# slitscan
+slitscan is a script inspired by [this Mastodon
+post](https://fed.qaz.red/@elithebearded/113070315634312301). It takes a video
+file as input and allows you to "transpose" the frames of the video to view
+along the height or width axes instead of the "time" axis you normally watch a
+video along.
+
+## Usage
+Say you have a video file `foo.mkv`. To transpose along the height axis and save
+to `bar.mkv`, run
+```
+python slitscan.py foo.mkv bar.mkv --height
+```
+
+Similarly, to transpose along the width axis, run
+```
+python slitscan.py foo.mkv bar.mkv --width
+```
+
+## Details
+### Uh... what does this do?
+Check the linked post for another explanation and examples.
+
+To elaborate, you can think of a video as a 3D array of pixels. Say the axes of
+the array are the frame, height, and width, in that order. Then the entry (24,
+500, 900) gives you the pixel in the 499th row and 899th column of the 23rd
+frame of the video (we're 0-indexed). You can imagine "watching" a video as
+just iterating through the frame axis of that array and displaying each 2D
+slice.
+
+This program transposes that 3D array so you're instead iterating over the
+height or width axis and displaying *those* 2D slices. For instance, if you
+transpose along the height axis, then the first frame of the output video
+consists of the top row of pixels of every single frame of the original video.
+The second frame is then the second row of every single original frame, and so
+on. Instead of viewing each original frame one by one, it's like you're viewing
+them all at once, but only one horizontal line of pixels at a time.
+
+### But why?
+The author of that Mastodon post mentioned that he wrote a bash script to do
+this that took a *a couple of days* to run for a short clip. I wanted to see if
+I could make it faster (and I did - this runs on the order of a few *minutes*
+for similarly short clips). It might be possible to make this script even
+faster, but I couldn't figure out how without the script using too much memory.
+
+### Is this even useful?
+I would love to find out that it is!