Introduction

PaletteFilter is a CircuitPython helper class for replacing color index values in a displayio.Palette object. A target color along with a tolerance parameter determine the range of color values to be replaced. The class creates a new palette object with the changes. The replacement color value (or None for transparency) is substituted for the original palette entry and placed into the new palette object, PaletteFilter.palette.

The filter uses a linear Euclidean comparison incorporating vision perception ('redmean') approximation to test palette color values with the specified target color. https://en.wikipedia.org/wiki/Color_difference

For comparing a single color value, use the cedargrove_palettefilter.compare_colors() helper function.

Dependencies

This driver depends on:

• Adafruit CircuitPython

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle or individual libraries can be installed using circup.

Installing to a Connected CircuitPython Device with Circup

Make sure that you have circup installed in your Python environment. Install it with the following command if necessary:

pip3 install circup

With circup installed and your CircuitPython device connected use the following command to install:

circup install cedargrove_palettefilter

Or the following command to update an existing version:

circup update

Usage Example

import displayio
from cedargrove_palettefilter import PaletteFilter

# Define the transparent color and tolerance values
TARGET_COLOR = 0x080808
FILL_COLOR = None
TOLERANCE = 4

# Make a displayio palette and set value(s) to transparent
SOURCE_COLORS = [
    0x000000,
    0x010101,
    0x020202,
    0x030303,
    0x040404,
    0x050505,
    0x060606,
    0x070707,
    0x080808,
    0x090909,
]
SOURCE_PALETTE = displayio.Palette(len(SOURCE_COLORS))
for index, color in enumerate(SOURCE_COLORS):
    SOURCE_PALETTE[index] = SOURCE_COLORS[index]

# Set a source palette value to transparent
SOURCE_PALETTE.make_transparent(3)

# Instantiate paletteFilter
filter = PaletteFilter(SOURCE_PALETTE, TARGET_COLOR, FILL_COLOR, TOLERANCE)
print(f"target_color: {hex(filter.target_color)}")

print("------")
print("source palette:")
print("index, color, transparency")
for index, color in enumerate(SOURCE_PALETTE):
    print(index, hex(color), SOURCE_PALETTE.is_transparent(index))

print("------")
print("new palette:")
print("index, color, transparency")
for index, color in enumerate(filter.palette):
    print(index, hex(color), filter.palette.is_transparent(index))

while True:
    pass

Documentation

API documentation for this library can be found in PaletteFilter_API.

For information on building library documentation, please check out this guide.

Contributing

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.