Semaphore

About Semaphore

Semaphore is a browser-based tool that converts images (PNG, JPG, WebP, GIF) into ASCII art. Processing happens locally via HTML canvas, with no files uploaded to a server; the production site sets a Content-Security-Policy of connect-src 'none' to prevent outbound network requests, and the tool continues to work offline once loaded. Users can adjust charset, column count, brightness, contrast, invert, and color while the output redraws live.

The tool offers six charsets, including classic ramps, block characters, binary, and a braille-based dot matrix for higher detail. Output can be copied as plain text, downloaded as a .txt file, exported as a PNG image, or saved as a share card that includes the conversion settings.

It is aimed at developers and others who need image-derived content in text-only contexts, such as README banners, CLI splash screens, commit messages, or plain-text channels like email and chat. The site is static, hosted on Cloudflare Pages, requires no account or sign-up, and has no watermark or usage quota. The engine's source code is available on GitHub.

Key features

• Converts images to ASCII art entirely in-browser with no upload
• Six charsets including classic ramps, blocks, binary and braille dot matrix
• Adjustable columns, brightness, contrast, invert and color while previewing live
• Exports as copied plain text, downloadable .txt, rendered PNG, or a branded share card
• Works offline once the page and font are cached
• Production CSP sets connect-src 'none' so no outbound network requests can be made

Frequently asked questions