Ascii flowchart drawing web app has most affordances one would expect of a modern drawing tool. site 
+-------+ +------+ | Input +----->Output| |Process| |Buffer| +---+---+ +------+ | | +---v---+ | Error | |Reports| +-------+
For example, move and resize boxes.
+--------------+ | | +------+ | Input +-------->Output| | Process | |Buffer| | | +------+ +-------+------+ | +---v---+ | Error | |Reports| +-------+
Copy these diagrams and continue editing after import.
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Convert ascii diagrams into svg. github
REXPaint is a powerful and user-friendly ASCII art editor. Windows-only, but runs under Wine in Linux/OSX. site