ConvertHGR Core — Browser Parity Port

Parity reference fixtures pending HGR FPS: —

Conversion controls

Dithering

PIX
Total distributed error: 8 / 16
0

Colour matching

80%
1%

Image preparation

Histogram uses a browser approximation until the external ImgSource equalizer is reference-calibrated.
130%
0
0

Conversion engine

WASM initializes on first conversion.
Open an image to begin.

Source / processed RGB

Drop an image here or use Open Image…

Apple II HGR output

X/Y
—
Processed RGB
—
Palette
—
Byte
—
Phase
—
HGR offset
—
8,192-byte HGR page

Parity diagnostics

Structural tests run locally. Quantizer hashes are reported but remain “reference pending” until desktop ConvertHGR golden fixtures are embedded.
FixtureStatusTimeHGR SHA-256
No tests run.

Implementation status

This file implements the ConvertHGR-compatible seven-pixel / 256-pattern quantizer, palette phases, candidate-horizontal D/E diffusion, A/B/C/F error propagation, ordered modes, colour metrics, five resize filters, HGR packing, and Apple II 8 KB memory interleave.

Parity is deliberately not claimed until reference fixtures generated by a fixed-seed desktop ConvertHGR build match byte-for-byte. Histogram Stretch is explicitly a compatibility approximation because the original delegates that operation to the external ImgSource library.

Behavioral reimplementation based on ConvertHGR by Mike Brent (Tursi / HarmlessLion). The original project should be credited and its redistribution terms reviewed before distributing a derived port.