import type { RGB } from './types.js';
import { AsciiFrame } from './frame.js';
export declare const PALETTE_VERSION = "palette-v1";
/** Largest palette accepted. A GPU uniform carries it, so it has a ceiling. */
export declare const MAX_PALETTE_COLORS = 256;
/**
 * Ordered dither by Bayer matrix size. Error diffusion (Floyd–Steinberg and
 * kin) is deliberately absent: it carries error from cell to cell in scan
 * order, which a GPU pass cannot do in parallel and stay exact.
 */
export type DitherKind = 'none' | 'bayer2' | 'bayer4' | 'bayer8';
export interface PaletteOptions {
    /** 1..256 colours. Ties between equally near entries go to the earlier one. */
    colors: readonly RGB[];
    /** Default 'none'. */
    dither?: DitherKind;
    /**
     * Dither amplitude in 0..255 channel units, default 64: the threshold offsets
     * span roughly ±spread/2. Around the gap between neighbouring palette colours
     * is a good value; much more turns gradients into noise.
     */
    spread?: number;
}
/** A palette reduced to what the per-cell step reads. */
export interface ResolvedPalette {
    /** Packed 0xBBGGRR, palette order. */
    colors: Uint32Array;
    /** Bayer matrix side: 1 (no dither), 2, 4 or 8. */
    size: number;
    /** Threshold offset per matrix position, row-major, size² entries. */
    offsets: Int32Array;
}
/** Validate and pack a palette for {@link quantizeFrame} or a GPU upload. */
export declare function resolvePalette(palette: PaletteOptions): ResolvedPalette;
/**
 * Snap one packed colour to the palette at cell (cx, cy). The alpha byte is
 * carried through; the result's RGB is always a palette entry.
 */
export declare function quantizeColor(c: number, cx: number, cy: number, palette: ResolvedPalette): number;
/**
 * The frame with its colour planes snapped to `palette` (palette-v1, §22).
 * Glyphs, flags and grid are shared with the input, not copied. `mono` and
 * `glyph` frames have no per-cell colour to snap and come back as they are.
 */
export declare function quantizeFrame(frame: AsciiFrame, palette: PaletteOptions | ResolvedPalette): AsciiFrame;