Open-Source AI Whiteboard PenEcho: Real-Time Interaction for Handwritten Formulas

Scobleizer · x · 2026-07-19

A Reddit user has developed an open-source whiteboard app called **PenEcho**. It allows users to handwrite math formulas, physics equations, or draw sketches on a canvas, with an AI model providing real-time feedback and answers right next to the handwriting. - **Core Features**: Offers a seamless 20000 x 20000 pixel canvas, loading only areas with handwriting to save resources; supports local execution and is compatible with models like Claude, OpenAI, and Codex. - **Technical Highlights**: The model can not only recognize handwritten text but also understand the spatial relationships of incomplete equations and sketches, inferring the user's true intent. - **Developer's Perspective**: This interactive experience, combining handwriting with spatial reasoning, was technically impossible just six months ago and represents a new paradigm for future scientific research and thinking workflows.

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