About

ANSI art encodes visual information within the constraints of monospaced character grids and a fixed 16-color palette defined by ECMA-48 / ISO 6429. A single misplaced escape sequence renders the entire downstream output as garbage in most terminal emulators. This editor operates on a cols × rows grid where each cell stores a character, a foreground color index, and a background color index. It implements Bresenham's line algorithm for precise diagonal strokes and iterative BFS flood fill to avoid recursion limits on large canvases. Export produces optimized ANSI escape sequences that only emit color-change codes when the palette actually shifts between adjacent cells, reducing output size by roughly 40% compared to naive per-cell encoding.

The tool assumes a standard 80×24 terminal geometry by default. Grids exceeding 200 columns may render incorrectly in terminals that do not support line wrapping suppression. Box-drawing characters (U+2500 block) require a font with complete Unicode coverage. Pro tip: test your exported art in at least two terminal emulators - rendering of block elements like ▄ and █ varies between xterm, iTerm2, and Windows Terminal.

Formulas

The line tool uses Bresenham's algorithm to determine which grid cells to fill between two endpoints. Given start cell (x₀, y₀) and end cell (x₁, y₁):

dx = |x₁ − x₀|

dy = −|y₁ − y₀|

err = dx + dy

At each step, the error term err is tested. If 2err ≥ dy, advance horizontally and add dy to err. If 2err ≤ dx, advance vertically and add dx to err. This yields an integer-only, branch-minimal rasterization with O(max(dx, |dy|)) time complexity.

ANSI export uses SGR (Select Graphic Rendition) sequences:

ESC[38;5;fgm - set foreground to color index fg

ESC[48;5;bgm - set background to color index bg

ESC[0m - reset all attributes

Where fg and bg are integers 0 - 15 corresponding to the standard ANSI color indices. The optimizer tracks the previous cell's colors and only emits a new SGR sequence when either fg or bg differs from the predecessor, reducing byte count significantly for regions of uniform color.

Reference Data

Character	Unicode	Name	Usage
─	U+2500	Box Light Horizontal	Horizontal lines
│	U+2502	Box Light Vertical	Vertical lines
┌	U+250C	Box Light Down Right	Top-left corner
┐	U+2510	Box Light Down Left	Top-right corner
└	U+2514	Box Light Up Right	Bottom-left corner
┘	U+2518	Box Light Up Left	Bottom-right corner
├	U+251C	Box Light Vertical Right	Left T-junction
┤	U+2524	Box Light Vertical Left	Right T-junction
┬	U+252C	Box Light Down Horizontal	Top T-junction
┴	U+2534	Box Light Up Horizontal	Bottom T-junction
┼	U+253C	Box Light Vertical Horizontal	Cross junction
═	U+2550	Box Double Horizontal	Double horizontal line
║	U+2551	Box Double Vertical	Double vertical line
╔	U+2554	Box Double Down Right	Double top-left corner
╗	U+2557	Box Double Down Left	Double top-right corner
╚	U+255A	Box Double Up Right	Double bottom-left corner
╝	U+255D	Box Double Up Left	Double bottom-right corner
█	U+2588	Full Block	Solid fill, pixel art
▓	U+2593	Dark Shade	75% density shading
▒	U+2592	Medium Shade	50% density shading
░	U+2591	Light Shade	25% density shading
▄	U+2584	Lower Half Block	Sub-cell vertical resolution
▀	U+2580	Upper Half Block	Sub-cell vertical resolution
▌	U+258C	Left Half Block	Sub-cell horizontal resolution
▐	U+2590	Right Half Block	Sub-cell horizontal resolution
●	U+25CF	Black Circle	Decorative, bullets
○	U+25CB	White Circle	Decorative, status indicators
♦	U+2666	Black Diamond	Decorative elements
★	U+2605	Black Star	Rating, decoration
♠	U+2660	Black Spade	Card art, decoration
♥	U+2665	Black Heart	Card art, decoration

Frequently Asked Questions

The exported sequences use the 256-color SGR format (ESC[38;5;Xm / ESC[48;5;Xm) which is supported by xterm, iTerm2, GNOME Terminal, Windows Terminal, and most modern emulators. Older terminals like the native Windows cmd.exe prior to Windows 10 version 1511 do not support these codes. The plain text export strips all escape sequences for maximum compatibility.

Box-drawing characters reside in the Unicode U+2500 - U+257F block. Your terminal's font must include these glyphs. Monospace fonts with full coverage include DejaVu Sans Mono, Consolas, Fira Code, and JetBrains Mono. If your terminal defaults to a bitmap font without these codepoints, the characters render as replacement glyphs.

The implementation uses iterative breadth-first search (BFS) with an explicit queue rather than recursive depth-first search. Recursive flood fill on an 80×24 grid (1,920 cells) risks hitting JavaScript's call stack limit (~10,000-25,000 frames depending on the engine). The BFS approach uses heap memory for the queue, which is limited only by available RAM - easily handling grids up to 200×100 (20,000 cells).

The plain text export works directly with any system that supports Unicode text. For IRC specifically, you would need mIRC color codes (Ctrl+K format) rather than ANSI escape sequences - this editor produces ANSI/VT100 sequences designed for terminal emulators. BBS systems using ANSI.SYS (such as Synchronet or Mystic BBS) are fully compatible with the ANSI export format.

The editor supports grids up to 200 columns by 100 rows (20,000 cells). Canvas rendering remains smooth because only dirty cells are repainted - a full redraw of 20,000 cells at 12×16 pixel cell size produces a 2400×1600 canvas, well within GPU texture limits. The undo stack stores full grid snapshots capped at 50 levels. At maximum grid size, each snapshot occupies approximately 600 KB of memory, so the full stack uses about 30 MB.

Naive encoding emits a foreground SGR sequence (7-12 bytes), a background SGR sequence (7-12 bytes), and a reset (4 bytes) for every single cell. For an 80×24 grid, that produces roughly 35-55 KB. The optimized encoder tracks the current foreground and background state and only emits new SGR codes when colors change between adjacent cells. For typical ANSI art with large uniform-colored regions, this reduces output by 40-60%, yielding files around 15-25 KB.