# Color Grade

> Color Grade AI

- Skill: `diegosouzapw/color-grade` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add diegosouzapw/color-grade`
- Raw SKILL.md: https://api.skillmd.com/api/skills/diegosouzapw/color-grade/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: diegosouzapw (https://skillmd.com/u/diegosouzapw)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/diegosouzapw/color-grade

---


# Color Grade AI

Generate targeted .cube 3D LUTs for color correction. Works with DaVinci Resolve and Adobe Premiere Pro.

## Quick Start

```bash
# Generate a LUT (presets defined in presets.yml)
ruby generate_lut.rb <type> <output_path> [--strength=0.0-1.0]

# Analyze a frame for color stats
ruby analyze_frame.rb <image_path> <x1,y1,x2,y2> [label]

# Regenerate docs from presets.yml
ruby generate_docs.rb
```

## Config-Driven Presets

All LUT types are defined in `presets.yml`. Each preset is a pipeline of ordered processing steps (exposure, black crush, skin correction, etc.). Adding a new LUT type means adding a YAML entry — no Ruby code changes needed.

## Available LUT Types

| Type | What it fixes |
|------|--------------|
| `night_warm_fix` | **All-in-one** for underexposed scenes with warm/red practicals. ~1 stop lift + skin hue shift + black crush. No desaturation — preserves vivid reds. Use with just AMIRA. |
| `night_purple_fix` | **All-in-one** for underexposed scenes with purple/magenta stage lighting. RGB rebalancing + ~2 stop lift + purple desat + skin hue shift + black crush. Preserves atmospheric purple while fixing skin. |
| `yellow_fix` | Warm amber/yellow cast from stage lighting. H=10-60, 55% desat. |
| `red_skin_fix` | Sunburnt/flushed red skin from warm practicals. Hue shift to peach, skin-only targeting. |
| `overexposure_fix` | Scene-wide ~1 stop reduction with highlight rolloff. |
| `underexposure_fix` | Scene-wide ~1.2 stop lift with shadow recovery. |
| `black_crush` | Crushes milky/lifted blacks below 12% to true black. |
| `skin_highlight_fix` | Subtle skin-only highlight rolloff above 70% luminance. |

## Workflow

1. Extract a frame: `ffmpeg -i video.mov -ss 00:00:30 -frames:v 1 frame.png`
2. Analyze regions: `ruby analyze_frame.rb frame.png 1500,600,2000,900 skin`
3. Generate appropriate LUT: `ruby generate_lut.rb overexposure_fix output.cube`
4. Apply in your NLE on an adjustment layer / node after your main conversion LUT

## Applying LUTs

**DaVinci Resolve:** Add a serial node after your conversion LUT node. Right-click the node, select LUT, browse to the .cube file.

**Adobe Premiere Pro:** Add Lumetri Color effect on an adjustment layer. Go to Creative tab, click the Look dropdown, browse to the .cube file.

## Stacking LUTs

LUTs can be stacked on separate adjustment layers / nodes. Common stacks:

**Night scene with warm practicals (simplest):**
1. Camera conversion LUT (e.g. AMIRA LogC to Rec.709)
2. Night Warm Fix (single LUT handles everything)

**Night scene with purple stage lighting:**
1. Camera conversion LUT (e.g. AMIRA LogC to Rec.709)
2. Night Purple Fix (single LUT handles everything)

**Overexposed footage:**
1. Camera conversion LUT
2. Overexposure Fix
3. Black Crush

**Underexposed footage:**
1. Camera conversion LUT
2. Underexposure Fix

## Node Order (DaVinci Resolve)

Professional serial node chain:
1. White Balance
2. Exposure
3. Main Conversion LUT
4. General Color Adjustments
5. Color Saturation/Boost
6. Noise Reduction
7. Black Levels
8. Vignette
9. Sharpening

## Color Science Notes

- **Desaturating warm tones in HSL produces brown/sepia.** Use hue shifting or RGB rebalancing instead.
- **Skin tones occupy H=10-35, S=0.08-0.45, L=0.25-0.75.** Use all three windows (hue + saturation + luminance) to isolate skin from light sources and colored objects.
- **LUTs have no spatial awareness.** They can't do noise reduction, sharpening, or distinguish adjacent pixels. Each pixel is transformed independently.
- **3D LUTs allow cross-channel operations.** Unlike 1D LUTs, a 3D LUT can change the red output based on the green and blue input values.

## Requirements

- Ruby 2.7+
- Python 3 with Pillow (for analyze_frame.rb)
- ffmpeg (for frame extraction)