# Opencv

> OpenCV computer vision library. Use for image processing.

- Skill: `majiayu000/opencv` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/opencv`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/opencv/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/opencv

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# OpenCV

OpenCV is the fundamental library for Image Processing. v5.0 (2025) modernizes deep learning support and licensing.

## When to Use

- **Image Manipulation**: Resizing, cropping, color space conversion (BGR -> RGB).
- **Classic CV**: Edge detection (Canny), Feature matching (SIFT/ORB).
- **Video I/O**: Reading/Writing webcams or video files.

## Core Concepts

### BGR

OpenCV reads images as Blue-Green-Red (not RGB) by default. History quirks.

### `cv::Mat`

The core matrix structure (in C++). In Python, it's just a NumPy array.

### DNN Module

Running darknet/onnx models directly in OpenCV (lightweight inference).

## Best Practices (2025)

**Do**:

- **Use it for Preprocessing**: `cv2.resize()` is highly optimized.
- **Use `headless`**: `pip install opencv-python-headless` for server deployments (smaller, no GUI deps).

**Don't**:

- **Don't implement Deep Learning training**: Use PyTorch. Use OpenCV only for inference/preprocessing.

## References

- [OpenCV Documentation](https://opencv.org/)