/** The built-in ramps. The sequential ones go from the least to the most; the diverging ones from the lowest through a neutral middle to the highest. */
export type HeatRampName = "ember" | "ocean" | "mono" | "balance" | "tide";
/** A built-in ramp: nine stops for a light page and nine for a dark one. */
export interface HeatRampDef {
    kind: "sequential" | "diverging";
    light: readonly string[];
    dark: readonly string[];
}
/**
 * The built-in ramps. On a light page a sequential ramp runs from a pale colour to a dark one, because the more there is the more ink it takes;
 * on a dark page it runs from near the ground to a bright one, because the more there is the more light it gives. A diverging ramp has its neutral
 * middle at the ground's colour and its two ends at full strength.
 */
export declare const HEAT_RAMPS: Readonly<Record<HeatRampName, HeatRampDef>>;
/** Names of the built-in ramps. */
export declare const HEAT_RAMP_NAMES: readonly HeatRampName[];
/**
 * A ramp for a layer: the name of a built-in one, a list of colour stops (the same on a light and a dark page), or a `light` and a `dark` list.
 * Stops are anything `safeColour` accepts.
 */
export type HeatRamp = HeatRampName | readonly string[] | {
    light: readonly string[];
    dark?: readonly string[];
};
/** A ramp, resolved: the stops for a light page, and for a dark one when it differs. */
export interface ResolvedRamp {
    name: HeatRampName | undefined;
    kind: "sequential" | "diverging";
    light: string[];
    dark: string[] | undefined;
}
/** The ramp a layer asks for; `ember` when it asks for none (`fallback` for a diverging statistic). */
export declare function resolveRamp(ramp: HeatRamp | undefined, fallback?: HeatRampName): ResolvedRamp;
/** The colour of step `k` of `steps` (0 to `steps - 1`) of some stops, as a hex colour (or the nearest stop for a colour that cannot be read without a browser). */
export declare function stepColour(stops: readonly string[], k: number, steps: number): string;
/** The step (0 to `steps - 1`) a value falls in, on a domain: the share of the way through it, to the nearest step. */
export declare function stepOf(value: number, domain: readonly [number, number], steps: number): number;