Palettize

🎨 A Python utility and CLI tool for generating, previewing, and exporting colormaps.

Palettize helps create colormaps for data visualization, GIS, and web mapping. It provides a simple command-line interface to:

• Generate colormaps from a list of colors or from built-in presets.
• Preview colormaps directly in the terminal.
• Export colormaps to various formats suitable for different applications.
• Customize interpolation color space, data scaling, and slicing.

Installation

uv pip install palettize

Or install from source:

git clone https://github.com/kovaca/palettize.git
cd palettize
uv pip install .

Usage

palettize --help

Key Commands

• palettize show: Render a colormap preview in your terminal.
• palettize create: Export a colormap to one or more file formats.
• palettize list: List available presets or exporters.

Examples

1. Show a built-in preset colormap:

   palettize show viridis

2. Show a custom gradient made of three colors:

   palettize show --colors "midnightblue,orange,gold"

3. Export the 'viridis' preset to a GDAL color ramp file: The --domain flag maps the colormap to your data's range.

   palettize create viridis --format gdal --output viridis_gdal.txt --domain 0,255

4. Create a custom colormap and export it to multiple formats: Use --steps to define the number of discrete colors in the output.

   palettize create -c "blue,white,red" --format qgis,mapgl \
     --output "output/rwb_{format}.{ext}" --steps 11 --name "RedWhiteBlue"

   This creates output/rwb_qgis.xml and output/rwb_mapgl.json.

5. List all available built-in presets:

   palettize list presets

6. Pass format-specific options during export: Use the -O or --option flag to pass key-value pairs to an exporter.

   # Tell the 'observable' exporter to create a diverging scale with a pivot
   palettize create RdBu -f observable --domain -5,10 -o plot.json \
     -O type=diverging -O pivot=0

Programmatic usage

You can also use Palettize from Python by importing the library.

from palettize import (
    create_colormap,
    list_available_presets,
    get_scaler_by_name,
)

# Inspect presets
print(list_available_presets()[:5])

# Create from preset
cmap = create_colormap(preset="custom/grayscale", name="Grayscale", cut_start=0.1, cut_end=0.9)
print(cmap.get_color(0.5))  # hex string
print(cmap.get_color(0.5, output_format="rgb_tuple"))

# Create from a list of colors
cmap2 = create_colormap(colors=["#0000ff", "white", "#ff0000"], name="BlueWhiteRed")

# Use a scaler to map data values onto the colormap
scaler = get_scaler_by_name("symlog", domain_min=-10, domain_max=10, linthresh=1, base=10)
print(cmap2.apply_scaler(3.2, scaler))

Features

• Flexible Colormap Creation: Generate colormaps from lists of colors (hex, RGB, named) or use built-in presets.
• Advanced Interpolation: Supports various color spaces for interpolation via the ColorAide library (e.g., Oklch, sRGB, LAB).
• Terminal Preview: Instantly visualize any colormap in your terminal.
• Multiple Export Formats: Supports common formats for GIS (GDAL, QGIS, SLD, Titiler) and web (MapLibre GL, Observable Plot).
• Customizable Scaling: Apply linear, power, sqrt, or log scaling to map your data domain to the colormap.
• Plugin System for Exporters: Easily extendable with new export formats.
• CLI with Rich Output: User-friendly command-line interface with clear help messages and rich formatting.

Available Presets

The incredibly useful cmap library is a core dependency used for presets. To see a list of colormap presets, run: palettize list presets

Available Export Formats

To see a list of all currently registered and available export formats, run: palettize list exporters