Get this effect
Switch to Code in your Claude Desktop App
Install the skill (once)
Show the prompt
Install the Recharm video effects skill: download https://recharm-growth-staging.s3.us-east-2.amazonaws.com/website/downloads/recharm-video-effects.zip and unzip it into ~/.claude/skillsAsk for the effect
Add a duotone to input.mp4 Shadow color (indigo): 35, 20, 95 Highlight color (coral): 255, 140, 105
Several videos, several effects, one ask
Put your clips in the folder, mention them with @, and ask for everything at once. Claude runs one tested script after another on each clip, then joins them.
Add a duotone to @clip1.mp4, put a sale badge on @clip2.mp4, give @clip3.mp4 a VHS look, then join all three with crossfades.
Settings you can change
Ask Claude to change any of these, or edit them at the top of the command.
| Setting | Default | What it does |
|---|---|---|
DARK_R, DARK_G, DARK_B | 35, 20, 95 | Shadow color (indigo). |
LIGHT_R, LIGHT_G, LIGHT_B | 255, 140, 105 | Highlight color (coral). |
BLACK | 50 | Input brightness that becomes the pure shadow color. Raise it for more indigo. |
WHITE | 240 | Input brightness that becomes the pure highlight color. Lower it for more coral. |
Without the skill
Don’t want to install the skill? Paste this prompt into Claude Code and Claude writes the command itself.
Show the prompt
Give input.mp4 a duotone look for its whole length: turn each frame to grayscale, stretch brightness 50 to 240 to the full range (clip anything outside), then map that brightness onto a straight blend between two colors, indigo (35, 20, 95) for the darkest pixels and coral (255, 140, 105) for the brightest. No other colors should be left in the picture. Keep the size, 30fps and the audio, use ffmpeg, and save it as output.mp4.Run it without Claude
This is the exact command we tested. Save it as duotone.sh and run:
sh duotone.sh input.mp4 output.mp4Show the command
#!/bin/sh
# Duotone: map the picture's brightness onto two colors, deep indigo in the shadows and coral in the highlights.
# Usage: sh duotone.sh input.mp4 output.mp4
# Needs ffmpeg.
set -e
IN="$1"; OUT="$2"
DARK_R=35; DARK_G=20; DARK_B=95 # shadow color (indigo)
LIGHT_R=255; LIGHT_G=140; LIGHT_B=105 # highlight color (coral)
BLACK=50 # input brightness that becomes the pure shadow color
WHITE=240 # input brightness that becomes the pure highlight color
# brightness from 0 (shadow color) to 1 (highlight color), after stretching BLACK..WHITE to the full range
TONE="clip((val-$BLACK)/($WHITE-$BLACK),0,1)"
ffmpeg -y -i "$IN" -vf "format=gray,format=gbrp,lutrgb=r='$DARK_R+($LIGHT_R-$DARK_R)*$TONE':g='$DARK_G+($LIGHT_G-$DARK_G)*$TONE':b='$DARK_B+($LIGHT_B-$DARK_B)*$TONE',format=yuv420p" \
-r 30 -c:v libx264 -crf 18 -c:a copy "$OUT"
