RGBA Export Format

The RGBA exporter creates plaintext files with CSS-compatible RGBA color values.

Format Details

Property	Value
Identifier	rgba
Extension	.txt
Use case	CSS, web development, alpha transparency

Output Format

rgba(68, 1, 84, 255)
rgba(72, 40, 120, 255)
rgba(62, 73, 137, 255)
rgba(49, 104, 142, 255)
rgba(38, 130, 142, 255)
rgba(31, 158, 137, 255)
rgba(53, 183, 121, 255)
rgba(110, 206, 88, 255)
rgba(181, 222, 43, 255)
rgba(253, 231, 37, 255)

Each line contains RGBA values where R, G, B, and A are integers from 0-255.

CLI Usage

# Basic export
palettize create viridis --format rgba --output colors.txt

# Specific number of colors
palettize create viridis -f rgba -o colors.txt --steps 10

# Print to stdout
palettize create viridis -f rgba --steps 5

Python Usage

from palettize import create_colormap, get_scaler_by_name, get_exporter

cmap = create_colormap(preset="viridis")
scaler = get_scaler_by_name("linear", domain_min=0, domain_max=1)
exporter = get_exporter("rgba")

output = exporter.export(
    colormap=cmap,
    scaler=scaler,
    domain_min=0,
    domain_max=1,
    options={"num_colors": 10}
)

# Parse into usable format
import re
colors = []
for line in output.strip().split('\n'):
    match = re.match(r'rgba\((\d+), (\d+), (\d+), (\d+)\)', line)
    if match:
        colors.append(tuple(map(int, match.groups())))

print(colors)  # [(68, 1, 84, 255), (72, 40, 120, 255), ...]

Options

Option	Type	Default	Description
num_colors	int	256	Number of colors to generate

Use Cases

CSS Stylesheets

.gradient {
  background: linear-gradient(
    to right,
    rgba(68, 1, 84, 255),
    rgba(49, 104, 142, 255),
    rgba(253, 231, 37, 255)
  );
}

Semi-transparent Colors

The RGBA format preserves alpha values, useful for overlays:

.overlay {
  background-color: rgba(68, 1, 84, 128);  /* 50% opacity */
}

JavaScript Arrays

const colors = [
  'rgba(68, 1, 84, 255)',
  'rgba(72, 40, 120, 255)',
  'rgba(62, 73, 137, 255)'
];

// Use with Canvas
const ctx = canvas.getContext('2d');
ctx.fillStyle = colors[0];

Python Image Processing

from PIL import Image
import re

# Parse RGBA output
output = exporter.export(cmap, scaler, 0, 1, {"num_colors": 256})
colors = []
for line in output.strip().split('\n'):
    match = re.match(r'rgba\((\d+), (\d+), (\d+), (\d+)\)', line)
    if match:
        colors.append(tuple(map(int, match.groups())))

# Create a palette image
width, height = 256, 50
img = Image.new('RGBA', (width, height))
for x in range(width):
    for y in range(height):
        img.putpixel((x, y), colors[x])
img.save('colorbar.png')

Data Visualization Libraries

# Plotly
import plotly.express as px

colors_css = output.strip().split('\n')
fig = px.scatter(df, x='x', y='y', color='value',
                 color_continuous_scale=colors_css)

Alpha Channel

Unlike the Hex format, RGBA includes the alpha channel:

• Fully opaque: rgba(68, 1, 84, 255)
• 50% transparent: rgba(68, 1, 84, 128)
• Fully transparent: rgba(68, 1, 84, 0)

By default, Palettize colormaps are fully opaque (alpha=255).

Converting to CSS rgba() with Normalized Alpha

CSS rgba() typically uses alpha from 0-1, not 0-255. To convert:

def to_css_rgba(rgba_string):
    match = re.match(r'rgba\((\d+), (\d+), (\d+), (\d+)\)', rgba_string)
    if match:
        r, g, b, a = map(int, match.groups())
        return f'rgba({r}, {g}, {b}, {a/255:.2f})'
    return rgba_string

# rgba(68, 1, 84, 255) -> rgba(68, 1, 84, 1.00)