How to replace a colour in a video with another colour using FFmpeg

Some years back, I was perturbed … nay … triggerred by a news report. Like an SJW, my blood pressure … to use the language of these fools … literally shot up. The title of the report read something like Fans of actress so-and-so are tired of seeing this hairstyle on her! What? Don't the jerks have nothing better to do? And, what insect of a journalist thought this was newsworthy? Sheesh!

I was reminded of this news report when I saw an online video today. It distracted me so much that I decided to change the colour of the top that the person was wearing. I did that using FFmpeg, of course. To protect the innocent, I shall not use the same video as I explain how I did it.

Use huesaturation filter to replace colours

In the video that I used for this blog post, the lone speaker (Oceana — pronounced O-Sheena) wears a blue sweater. Using the huesaturation filter, I was able to change to several different to any other colour I wanted to.

To change all blue pixels to purple during playback:

ffplay \
  -vf "huesaturation=hue=150:saturation=0.5:colors=b:strength=20" \
  Reading-Christian-Booktube-s-favourite-books.mp4

To make the colour changes permanent:

ffmpeg -i Reading-Christian-Booktube-s-favourite-books.mp4 \
       -vf "huesaturation=hue=150:saturation=0.5:colors=b:strength=20" \
       -c:v libx264 -crf 21 -preset medium -tune film -pix_fmt yuv420p -r 24 \
       -c:a copy \
       Reading-Christian-Booktube-s-favourite-books-color-replaced.mp4

The range for hue filter option is from -180 to 180. In this range, you can cover all colours. For different shades of the same colour, you will have to adjust the saturation option (from -1.0 to 1.0). In the colors option, specify which primary colour you want to change — all reds, all greens, all blues or some combination thereof. The -pix_fmt option ensures compatibility with most playback devices.

Animation demo

Video demos

For the next video (featuring a green vine snake, I wrote a script to randomly change the colors as a function of time.

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