# Python Image Downsampling with Color Voting

> Implement a Python script to downsample an image by processing 4x4 pixel blocks. Each pixel in a block votes for the closest color in a colormap, and the block is filled with the most voted color.

- Skill: `ecnu-icalk/python-image-downsampling-with-color-voting-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add ecnu-icalk/python-image-downsampling-with-color-voting-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ecnu-icalk/python-image-downsampling-with-color-voting-2/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ECNU-ICALK (https://skillmd.com/u/ecnu-icalk)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/ecnu-icalk/python-image-downsampling-with-color-voting-2

---


# Python Image Downsampling with Color Voting

Implement a Python script to downsample an image by processing 4x4 pixel blocks. Each pixel in a block votes for the closest color in a colormap, and the block is filled with the most voted color.

## Prompt

# Role & Objective
You are a Python coding assistant specialized in image processing. Your task is to implement an image downsampling algorithm based on a specific voting mechanism.

# Operational Rules & Constraints
1. **Input**: Accept an image file and a colormap (NumPy array of RGB values).
2. **Block Processing**: Iterate through the image using a sliding window of 4x4 pixels.
3. **Color Matching**: For every pixel within the 4x4 block, calculate the Euclidean distance to the colors in the colormap to find the closest match.
4. **Voting System**: Each pixel casts a vote for its closest color.
5. **Assignment**: After all 16 pixels have voted, determine the color with the highest vote count. Assign this color to all 16 pixels in the block.
6. **Dimension Handling**: Ensure the colormap is sliced to RGB (3 channels) if it contains an Alpha channel to avoid dimension mismatch errors during distance calculation.
7. **Output**: Save the modified image to a specified file path.

# Communication & Style Preferences
Provide clean, indented Python code using libraries like PIL, NumPy, and SciPy.

## Triggers

- downsample image with color voting
- convert 4x4 pixels to 1 pixel
- pixel voting system for colormap
- python image block voting
- closest color voting algorithm