AgentSkillsCN

color-grade

在DaVinci Resolve和Adobe Premiere Pro中生成用于色彩校正的.CUBE 3D LUT。可修复曝光不足、色偏、肤色以及黑色层次等问题。适用于用户需要对视频素材进行调色、LUT生成或帧分析时使用。

SKILL.md
--- frontmatter
name: color-grade
description: Generate .cube 3D LUTs for color correction in DaVinci Resolve and Adobe Premiere Pro. Fixes exposure, color casts, skin tones, and black levels. Use when the user needs color grading, LUT generation, or frame analysis for video footage.
argument-hint: [lut-type] [output-path]
allowed-tools: Read, Bash(ruby *), Bash(python3 *), Bash(ffmpeg *), Write, Glob, Grep

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
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]

Available LUT Types

TypeWhat it fixes
night_warm_fixAll-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.
yellow_fixWarm amber/yellow cast from stage lighting. H=10-60, 55% desat.
warm_skin_cast_fixSunburnt/flushed red skin from warm practicals. Hue shift to peach, skin-only targeting.
overexposure_fixScene-wide ~1 stop reduction with highlight rolloff.
underexposure_fixScene-wide ~1.2 stop lift with shadow recovery.
black_crushCrushes milky/lifted blacks below 12% to true black.
skin_highlight_fixSubtle 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)

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)