swatchify

Swatchify

A fast, cross-platform CLI tool that extracts dominant colors from images using k-means clustering.

Installation

Go Install (requires Go 1.21+)

go install github.com/james-see/swatchify@latest

Homebrew (macOS/Linux)

brew install james-see/tap/swatchify

Download Binary

Download the latest release for your platform from the Releases page.

Build from Source

git clone https://github.com/james-see/swatchify
cd swatchify
go build -o swatchify .

Usage

swatchify <image> [flags]

Examples

# Extract 5 dominant colors (default)
swatchify photo.jpg

# Extract 8 colors
swatchify logo.png -n 8

# Output as JSON
swatchify image.png --json

# Generate a palette PNG with hex labels
swatchify brand.png --png palette.png

# Generate palette and open it
swatchify brand.png --png palette.png --show

# Exclude white and black colors
swatchify mood.png --exclude-white --exclude-black

# Higher quality (slower, more accurate)
swatchify photo.jpg --quality 100

# Pipe JSON to file
swatchify image.jpg --json > palette.json

Flags

Flag	Short	Default	Description
--colors	-n	5	Number of dominant colors to extract
--json		false	Output in JSON format
--png			Generate palette PNG at specified path
--exclude-white		false	Exclude colors close to white
--exclude-black		false	Exclude colors close to black
--min-contrast		0	Minimum color distance between palette colors
--show		false	Open generated palette image after creation
--quality		50	Downscale quality 0-100 (higher = more accurate, slower)
--width		1000	Palette image width in pixels
--height		200	Palette image height in pixels

Supported Formats

• JPEG/JPG
• PNG
• WebP
• GIF (first frame)
• BMP
• TIFF

Output Formats

Text (default)

#112233
#AABBCC
#FFEEDD
#998877
#341212

JSON

{
  "image": "input.jpg",
  "colors": [
    {"hex": "#112233", "percentage": 34.5},
    {"hex": "#AABBCC", "percentage": 21.0},
    {"hex": "#FFEEDD", "percentage": 18.2},
    {"hex": "#998877", "percentage": 15.1},
    {"hex": "#341212", "percentage": 11.2}
  ]
}

Palette PNG

Generates a horizontal color strip with blocks sized proportionally to color prevalence. Each block displays its hex code with automatic contrast text (white on dark, black on light).

Performance

• Target execution time: < 300ms for typical images
• Memory footprint: < 100MB
• Images are automatically downscaled for processing speed

Run as API Server

Start swatchify as an HTTP server for REST API access:

swatchify serve --port 8080

Endpoints

POST /extract — Extract colors from uploaded image

# Basic usage
curl -X POST -F "[email protected]" http://localhost:8080/extract

# With options
curl -X POST \
  -F "[email protected]" \
  -F "colors=8" \
  -F "quality=100" \
  -F "exclude_white=true" \
  http://localhost:8080/extract

Response:

{
  "success": true,
  "colors": [
    {"hex": "#112233", "percentage": 34.5},
    {"hex": "#AABBCC", "percentage": 21.0}
  ]
}

GET /health — Health check

curl http://localhost:8080/health
# {"status": "ok"}

Form Parameters

Parameter	Type	Default	Description
image	file	required	Image file to analyze
colors	int	5	Number of colors to extract
quality	int	50	Quality 0-100
exclude_white	bool	false	Exclude near-white colors
exclude_black	bool	false	Exclude near-black colors
min_contrast	float	0	Minimum color distance

Use as a Library

Swatchify can be imported and used in your Go code:

package main

import (
    "fmt"
    "log"

    "github.com/james-see/swatchify/pkg/swatchify"
)

func main() {
    // Extract with default options (5 colors)
    colors, err := swatchify.ExtractFromFile("photo.jpg", nil)
    if err != nil {
        log.Fatal(err)
    }

    for _, c := range colors {
        fmt.Printf("%s (%.1f%%)\n", c.Hex, c.Percentage)
    }

    // Custom options
    opts := &swatchify.Options{
        NumColors:    8,
        Quality:      100,
        ExcludeWhite: true,
        ExcludeBlack: true,
        MinContrast:  30,
    }
    colors, _ = swatchify.ExtractFromFile("photo.jpg", opts)

    // Generate palette image
    swatchify.GeneratePalette(colors, "palette.png", nil)
}

Library API

// Extract from file path
colors, err := swatchify.ExtractFromFile(path string, opts *Options) ([]Color, error)

// Extract from image.Image
colors, err := swatchify.ExtractFromImage(img image.Image, opts *Options) ([]Color, error)

// Generate palette PNG
err := swatchify.GeneratePalette(colors []Color, outputPath string, opts *PaletteOptions) error

How It Works

1. Load and decode the input image
2. Downscale large images based on quality setting
3. Extract pixel data as RGB vectors
4. Run k-means++ clustering to find dominant colors
5. Sort clusters by population percentage
6. Apply any filters (white/black exclusion, min contrast)
7. Output results in requested format

License

MIT