ffmpeg-color-grading-chromakey

What this skill does

## CRITICAL GUIDELINES

### Windows File Path Requirements

**MANDATORY: Always Use Backslashes on Windows for File Paths**

When using Edit or Write tools on Windows, you MUST use backslashes (`\`) in file paths, NOT forward slashes (`/`).

---

## Quick Reference

| Task | Command |
|------|---------|
| Green screen removal | `-vf "chromakey=0x00FF00:0.3:0.1"` |
| Blue screen removal | `-vf "chromakey=0x0000FF:0.3:0.1"` |
| Apply LUT | `-vf "lut3d=cinematic.cube"` |
| Color curves | `-vf "curves=preset=vintage"` |
| Adjust saturation | `-vf "eq=saturation=1.5"` |
| Hue shift | `-vf "hue=h=30"` |
| White balance | `-vf "colortemperature=6500"` |

## When to Use This Skill

Use for **color manipulation operations**:
- Removing green/blue screen backgrounds
- Applying LUT color grading
- Color correction and enhancement
- Creating cinematic color looks
- HDR/SDR conversions
- Color keying for compositing

---

# FFmpeg Color Grading & Chromakey (2025)

Complete guide to color manipulation, green screen removal, LUT grading, and advanced color effects with FFmpeg.

## Green Screen (Chromakey) Removal

### Basic Chromakey

```bash
# Remove green screen (standard green 0x00FF00)
ffmpeg -i foreground.mp4 -i background.mp4 \
  -filter_complex "[0:v]chromakey=0x00FF00:0.3:0.1[fg];[1:v][fg]overlay" \
  -c:v libx264 -crf 18 output.mp4

# Parameters:
# - color: The key color (hex 0xRRGGBB)
# - similarity: How close to key color (0.0-1.0, lower = more precise)
# - blend: Edge softness (0.0-1.0, higher = softer edges)
```

### Chromakey Parameter Tuning

```bash
# Tight key (clean edges, may leave green fringe)
ffmpeg -i green_screen.mp4 -i background.jpg \
  -filter_complex "[0:v]chromakey=0x00FF00:0.1:0.0[fg];[1:v][fg]overlay" \
  output.mp4

# Loose key (removes all green, may eat into subject)
ffmpeg -i green_screen.mp4 -i background.jpg \
  -filter_complex "[0:v]chromakey=0x00FF00:0.5:0.2[fg];[1:v][fg]overlay" \
  output.mp4

# Balanced (recommended starting point)
ffmpeg -i green_screen.mp4 -i background.jpg \
  -filter_complex "[0:v]chromakey=0x00FF00:0.3:0.1[fg];[1:v][fg]overlay" \
  output.mp4
```

### Blue Screen Removal

```bash
# Remove blue screen
ffmpeg -i blue_screen.mp4 -i background.mp4 \
  -filter_complex "[0:v]chromakey=0x0000FF:0.3:0.1[fg];[1:v][fg]overlay" \
  output.mp4

# Chroma blue (common broadcast blue)
ffmpeg -i footage.mp4 -i background.mp4 \
  -filter_complex "[0:v]chromakey=0x0047AB:0.3:0.15[fg];[1:v][fg]overlay" \
  output.mp4
```

### Sample Green Screen Colors

| Name | Hex | Use Case |
|------|-----|----------|
| Pure Green | 0x00FF00 | Digital green screens |
| Chroma Green | 0x00B140 | Professional film/TV |
| Light Green | 0x90EE90 | Lighter backgrounds |
| Pure Blue | 0x0000FF | Digital blue screens |
| Chroma Blue | 0x0047AB | Professional broadcast |

### Advanced Chromakey with Despill

Green spill removal (green reflection on subject):

```bash
# Remove green screen with despill
ffmpeg -i green_screen.mp4 -i background.mp4 \
  -filter_complex "\
    [0:v]chromakey=0x00FF00:0.3:0.1,\
    colorbalance=gs=-0.1:gm=-0.1:gh=-0.1[fg];\
    [1:v][fg]overlay" \
  output.mp4

# More aggressive despill using hue filter
ffmpeg -i green_screen.mp4 -i background.mp4 \
  -filter_complex "\
    [0:v]chromakey=0x00FF00:0.3:0.1,\
    hue=s=0.9[fg];\
    [1:v][fg]overlay" \
  output.mp4
```

## Colorkey Filter (Transparency)

Colorkey creates actual transparency (alpha channel) instead of compositing:

```bash
# Create transparent video (WebM with alpha)
ffmpeg -i green_screen.mp4 \
  -vf "colorkey=0x00FF00:0.3:0.1" \
  -c:v libvpx-vp9 -pix_fmt yuva420p \
  output_transparent.webm

# Create transparent PNG sequence
ffmpeg -i green_screen.mp4 \
  -vf "colorkey=0x00FF00:0.3:0.1" \
  frame_%04d.png
```

### Colorkey vs Chromakey

| Feature | colorkey | chromakey |
|---------|----------|-----------|
| Output | Alpha channel | Composited |
| Format | Requires alpha support | Any format |
| Use | Create masks | Direct compositing |
| Formats | WebM, PNG, ProRes 4444 | MP4, MKV, etc. |

## LUT Color Grading

### Apply 3D LUT

```bash
# Apply .cube LUT file
ffmpeg -i input.mp4 \
  -vf "lut3d=cinematic.cube" \
  -c:v libx264 -crf 18 output.mp4

# Apply .3dl LUT
ffmpeg -i input.mp4 \
  -vf "lut3d=film_look.3dl" \
  output.mp4

# Specify interpolation method
ffmpeg -i input.mp4 \
  -vf "lut3d=lut.cube:interp=trilinear" \
  output.mp4
```

### LUT Interpolation Methods

| Method | Quality | Speed |
|--------|---------|-------|
| nearest | Lowest | Fastest |
| trilinear | Good | Fast |
| tetrahedral | Best | Slower |

```bash
# High quality LUT application
ffmpeg -i input.mp4 \
  -vf "lut3d=film.cube:interp=tetrahedral" \
  -c:v libx264 -crf 18 output.mp4
```

### Blend Original with LUT

```bash
# 50% LUT strength
ffmpeg -i input.mp4 \
  -filter_complex "\
    [0:v]split[a][b];\
    [a]lut3d=cinematic.cube[graded];\
    [b][graded]blend=all_expr='A*0.5+B*0.5'" \
  output.mp4

# Variable LUT intensity using colorbalance
ffmpeg -i input.mp4 \
  -vf "lut3d=lut.cube,colorbalance=rs=0:gs=0:bs=0" \
  output.mp4
```

### Popular LUT Styles

Create common looks without external LUTs:

```bash
# Teal and Orange (blockbuster look)
ffmpeg -i input.mp4 \
  -vf "colorbalance=rs=0.1:gs=-0.1:bs=-0.2:rm=0.05:gm=-0.05:bm=-0.1:rh=0.1:gh=-0.05:bh=-0.15" \
  output.mp4

# Vintage/Retro
ffmpeg -i input.mp4 \
  -vf "curves=preset=vintage,eq=saturation=0.8:contrast=1.1" \
  output.mp4

# High Contrast Cinematic
ffmpeg -i input.mp4 \
  -vf "eq=contrast=1.2:brightness=-0.05:saturation=1.1,unsharp=5:5:0.8" \
  output.mp4

# Desaturated/Bleach Bypass
ffmpeg -i input.mp4 \
  -vf "eq=saturation=0.5:contrast=1.3:brightness=-0.02" \
  output.mp4

# Warm/Golden Hour
ffmpeg -i input.mp4 \
  -vf "colortemperature=5000,eq=saturation=1.2:brightness=0.05" \
  output.mp4

# Cool/Moonlight
ffmpeg -i input.mp4 \
  -vf "colortemperature=8000,eq=saturation=0.9:brightness=-0.05" \
  output.mp4
```

## Color Curves

### Preset Curves

```bash
# Vintage look
ffmpeg -i input.mp4 -vf "curves=preset=vintage" output.mp4

# Cross process (film developing effect)
ffmpeg -i input.mp4 -vf "curves=preset=cross_process" output.mp4

# Negative image
ffmpeg -i input.mp4 -vf "curves=preset=negative" output.mp4

# Increase contrast
ffmpeg -i input.mp4 -vf "curves=preset=strong_contrast" output.mp4

# Lighter
ffmpeg -i input.mp4 -vf "curves=preset=lighter" output.mp4

# Darker
ffmpeg -i input.mp4 -vf "curves=preset=darker" output.mp4

# Linear contrast
ffmpeg -i input.mp4 -vf "curves=preset=linear_contrast" output.mp4

# Medium contrast
ffmpeg -i input.mp4 -vf "curves=preset=medium_contrast" output.mp4
```

### Custom Curves

```bash
# S-curve for contrast (RGB)
ffmpeg -i input.mp4 \
  -vf "curves=all='0/0 0.25/0.20 0.5/0.5 0.75/0.80 1/1'" \
  output.mp4

# Lift shadows, lower highlights
ffmpeg -i input.mp4 \
  -vf "curves=all='0/0.05 0.5/0.5 1/0.95'" \
  output.mp4

# Per-channel curves (R, G, B)
ffmpeg -i input.mp4 \
  -vf "curves=r='0/0 0.5/0.6 1/1':g='0/0 0.5/0.5 1/1':b='0/0 0.5/0.4 1/1'" \
  output.mp4

# Crushed blacks (film look)
ffmpeg -i input.mp4 \
  -vf "curves=all='0/0.03 0.15/0.15 0.5/0.5 0.85/0.85 1/1'" \
  output.mp4
```

## Color Balance

### colorbalance Filter

```bash
# Warm highlights, cool shadows
ffmpeg -i input.mp4 \
  -vf "colorbalance=rs=-0.1:gs=-0.05:bs=0.1:rh=0.1:gh=0.05:bh=-0.1" \
  output.mp4

# Parameters:
# rs/gs/bs = red/green/blue shadows (-1 to 1)
# rm/gm/bm = red/green/blue midtones (-1 to 1)
# rh/gh/bh = red/green/blue highlights (-1 to 1)
```

### Common Color Balance Presets

```bash
# Orange and Teal (cinematic)
ffmpeg -i input.mp4 \
  -vf "colorbalance=rs=0.15:bs