If you’re on MacOS, you can use Homebrew to install FFmpeg:

brew install ffmpeg

If you’re on Linux:

sudo apt install ffmpeg

And if you’re on Windows:

1. Download the pre-built binaries. Choose the Windows version and click on the link to download a static build.

2. Extract the downloaded ZIP file to a folder of your choice, e.g., C:\ffmpeg. I personally have a babyscripts folder for small CLI apps like this or yt-dlp.

3. Add the bin directory to your system’s PATH:

   • Open the Start Menu and search for “Environment Variables”, and click “Edit the system environment variables”.
   • In the System Properties window, click the “Environment Variables” button.
   • In the Environment Variables window, find the “Path” variable in the “System variables” section and select it. Click “Edit”.
   • Click “New” and add the path to the bin directory of your FFmpeg installation, e.g., C:\ffmpeg\bin.
   • Click “OK” to close all windows.

4. Verify the installation by opening Command Prompt and typing ffmpeg -version.

For MacOS/Linux, run the below command and then restart your terminal:

newCommand='
# Alias for converting videos from dark mode to light mode
convert-to-light-mode() {
    inputFileName=$1
    outputFileName=$2

    if [ -z "$outputFileName" ]; then
        fileBaseName="${inputFileName%.*}"
        suffix="-light-mode"
        fileExtension="${inputFileName##*.}"
        outputFileName="${fileBaseName}${suffix}.${fileExtension}"
    fi

    ffmpeg -i "$inputFileName" -vf "negate,hue=h=180,eq=contrast=1.2:saturation=1.1" "$outputFileName"
}
'

# Add command to bash and zsh
echo $newCommand >> ~/.bashrc
echo $newCommand >> ~/.zshrc

(thanks to @chriswblake for help with this part!)

Now, when you want to run the command, you run:

convert-to-light-mode input.mp4 output.mp4

# or

convert-to-light-mode my-video.mp4
# the output here would be my-video-light-mode.mp4

And here’s the equivalent for Windows!

# A function for converting videos from dark mode to light mode
function Convert-ToLightMode {
    param (
        [string]$inputFileName,
        [string]$outputFileName
    )

    if (-not $outputFileName) {
        $fileBaseName = [System.IO.Path]::GetFileNameWithoutExtension($inputFileName)
        $suffix = "-light-mode"
        $fileExtension = [System.IO.Path]::GetExtension($inputFileName)
        $outputFileName = "${fileBaseName}${suffix}${fileExtension}"
    }

    ffmpeg -i $inputFileName -vf "negate,hue=h=180,eq=contrast=1.2:saturation=1.1" $outputFileName
}

$profileContent = @"
function Convert-ToLightMode {
    param (
        [string]`$inputFileName,
        [string]`$outputFileName
    )

if (-not `$outputFileName) {
        `$fileBaseName = [System.IO.Path]::GetFileNameWithoutExtension(`$inputFileName)
        `$suffix = "-light-mode"
        `$fileExtension = [System.IO.Path]::GetExtension(`$inputFileName)
        `$outputFileName = "`$fileBaseName`$suffix`$fileExtension"
    }

    ffmpeg -i `$inputFileName -vf "negate,hue=h=180,eq=contrast=1.2:saturation=1.1" `$outputFileName
}
"@

Add-Content -Path $PROFILE -Value $profileContent

To use this, you would run it like so:

Convert-ToLightMode -inputFileName "input.mp4" -outputFileName "output.mp4"

# or

Convert-ToLightMode -inputFileName "my-video.mp4"
# the output here would be my-video-light-mode.mp4

Something that you can ALSO do with this script is export the light mode version as a .gif image!

MacOS/Linux:

convert-to-light-mode input.mp4 output.gif

Windows:

Convert-ToLightMode -inputFileName "input.mp4" -outputFileName "output.gif"

Wow! By the way, if you want your original video to be a .gif too, you can run it fairly plainly with FFmpeg:

ffmpeg -i input.mp4 output.gif