Color Interpolation

When creating colormaps, the choice of color space for interpolation significantly affects how colors blend between stops. Palettize supports multiple interpolation spaces via the ColorAide library.

Why Interpolation Space Matters

Consider a gradient from blue to yellow:

sRGB interpolation: May produce muddy greens in the middle
Oklch interpolation: Produces vibrant, perceptually uniform transitions

The interpolation space determines the path colors take through color space when blending.

Available Color Spaces

Oklch (Default)

Oklch is a perceptually uniform color space based on human vision. It provides:

Consistent perceived brightness across the gradient
Vibrant, natural-looking color transitions
No unexpected muddy colors

palettize show --colors "blue,yellow" --space oklch

This is the default and recommended for most use cases.

sRGB

Standard RGB interpolation. Colors blend in the same space as computer displays.

palettize show --colors "blue,yellow" --space srgb

Characteristics:

Fast computation
May produce muddy/desaturated midpoints
Common in web/CSS gradients

LAB (CIELAB)

A perceptually uniform color space from 1976.

palettize show --colors "blue,yellow" --space lab

Characteristics:

Good perceptual uniformity
Better than sRGB for scientific visualization
May produce some hue shifts

HCL (LCH)

Cylindrical representation of LAB, using Hue, Chroma, and Lightness.

palettize show --colors "blue,yellow" --space hcl

Characteristics:

Intuitive hue interpolation
Good for rainbow-like gradients
May have chroma issues at extreme values

HSL

Hue, Saturation, Lightness - a common web color model.

palettize show --colors "blue,yellow" --space hsl

Characteristics:

Intuitive for designers
Non-uniform perceptually
Can produce unexpected results

Comparing Interpolation Spaces

Visual Comparison

# Compare the same gradient in different spaces
palettize show --colors "blue,yellow" --space srgb --height 2
palettize show --colors "blue,yellow" --space oklch --height 2
palettize show --colors "blue,yellow" --space lab --height 2

Python Comparison

from palettize import create_colormap

colors = ["blue", "yellow"]

for space in ["srgb", "oklch", "lab", "hcl"]:
    cmap = create_colormap(colors=colors, interpolation_space=space)
    midpoint = cmap.get_color(0.5)
    print(f"{space}: {midpoint}")

Output:

srgb: #808000
oklch: #a3b852
lab: #9ab356
hcl: #8cb866

Notice how sRGB produces a darker, muddier olive color while the perceptual spaces produce brighter, more vibrant midpoints.

Choosing a Color Space

Use Oklch When:

Creating scientific visualizations
You want perceptually uniform brightness
Working with diverging colormaps
Default choice for most applications

Use sRGB When:

Matching existing CSS/web gradients
Performance is critical
You specifically need RGB blending behavior

Use LAB/HCL When:

Porting from tools that use these spaces
Working with color science applications
Creating perceptually balanced palettes

Impact on Exports

The interpolation space affects the colors sampled during export:

from palettize import create_colormap, get_scaler_by_name, get_exporter

cmap_srgb = create_colormap(colors=["blue", "yellow"], interpolation_space="srgb")
cmap_oklch = create_colormap(colors=["blue", "yellow"], interpolation_space="oklch")

scaler = get_scaler_by_name("linear", domain_min=0, domain_max=1)
exporter = get_exporter("hex")

# Different midpoint colors
print(exporter.export(cmap_srgb, scaler, 0, 1, {"num_colors": 3}))
print(exporter.export(cmap_oklch, scaler, 0, 1, {"num_colors": 3}))

Best Practices

Start with Oklch: It’s the default for good reason
Test visually: Use palettize show to preview before exporting
Consider your data: Scientific data often benefits from perceptually uniform spaces
Be consistent: Use the same space throughout a project

Perceptual Uniformity Explained

A “perceptually uniform” color space means equal numeric changes produce equal perceived changes in color.

In sRGB:

Changing R from 100→150 might look very different from 150→200
The same numeric difference produces different perceived differences

In Oklch:

Equal steps in lightness produce equal perceived brightness changes
Colors blend more naturally

This is especially important for data visualization where color represents numeric values.

Advanced: Color Space Reference

Space	Type	Perceptual	Hue Handling
`srgb`	RGB	No	N/A
`oklch`	Cylindrical	Yes	Excellent
`lab`	Rectangular	Yes	Good
`hcl`	Cylindrical	Yes	Good
`hsl`	Cylindrical	No	Direct
`hsv`	Cylindrical	No	Direct
`okhsl`	Cylindrical	Yes	Good
`okhsv`	Cylindrical	Yes	Good

Palettize supports any color space that ColorAide supports. See the ColorAide documentation for the full list.