Image to ANSI ASCII renderer library

• Type: feature
• Track: B
• Status: done
• Owner: Antigravity (Track B)
• Opened: 2026-06-20
• Blocked-by: feature-rtl-image-bitmap-library, feature-terminal-ansi-library
• Relation: Track B renderer library. Lets console demos display rich scene art without embedding renderer logic in each app.

Goal

Convert a bitmap into terminal-friendly art. The primary target is ANSI truecolor half-block rendering, with plain ASCII as a portable fallback.

Render modes

• Plain luminance ASCII using a ramp such as .:-=+*#%@.
• ANSI colored ASCII using foreground color per cell.
• ANSI truecolor half-block mode:
  • glyph ▀
  • foreground color = upper source pixel
  • background color = lower source pixel
  • one terminal cell represents two vertical pixels

Surface sketch

• RenderAscii(const img: TBitmap; width, height: Integer): AnsiString
• RenderAnsi256(...)
• RenderAnsiTrueColorHalfBlock(...)
• optional: dithering, aspect correction, palette reduction, gamma correction

Acceptance

• Tiny bitmap fixtures render to exact expected byte strings.
• Half-block rendering handles odd image heights deterministically.
• The unit depends on the image core and terminal ANSI helpers, not on PNG.
• examples/adventure can load or embed pre-rendered .ansi scenes generated by this library or an equivalent host tool.

Notes

• Runtime rendering and offline asset generation should share the same algorithm eventually.
• Keep the first slice deterministic; art quality tweaks can come later.

RESOLVED 2026-06-21 (Track B)

Implemented lib/rtl/ansirender.pas providing ASCII rendering, ANSI 256-color ASCII rendering, and truecolor ANSI half-block rendering. Integrated local variables for indexing string constants to work around compiler limitations. Added test/lib_ansirender.pas unit test to verify exact output bytes, and added it to the Makefile lib-test target.

Resolved-in: 2d7e65c (finalizing commit)