/** Built-in shell chrome wash presets. */
export type ShellGradientPreset = 'none' | 'cool' | 'neutral' | 'warm' | 'fresh';
export declare const SHELL_GRADIENT_PRESETS: ShellGradientPreset[];
/** Wash presets shown after the `none` option in pickers. */
export declare const SHELL_GRADIENT_WASH_PRESETS: Exclude<ShellGradientPreset, 'none'>[];
/** Default wash when `gradient-preset` is omitted. */
export declare const DEFAULT_SHELL_GRADIENT_PRESET: ShellGradientPreset;
export declare const SHELL_GRADIENT_PRESET_LABELS: Record<ShellGradientPreset, string>;
export interface ShellGradientStop {
    color: string;
    position: number;
}
export interface ShellGradientRecipe {
    opacity: number;
    stops: readonly ShellGradientStop[];
}
export interface ShellGradientPickerPreview {
    backgroundColor: string;
    backgroundImage?: string;
    opacity?: number;
}
export interface ShellGradientPickerOption {
    value: ShellGradientPreset;
    label: string;
    preview: ShellGradientPickerPreview;
}
export interface ShellGradientPickerSection {
    options: ShellGradientPickerOption[];
}
export declare function shellGradientPresetStopToken(preset: ShellGradientPreset): string | null;
export declare function shellGradientPresetRecipe(preset: ShellGradientPreset): ShellGradientRecipe | null;
export declare function shellGradientPresetOpacity(preset: ShellGradientPreset): string;
export declare function isShellGradientPreset(value: string): value is ShellGradientPreset;
/**
 * Coerce unknown/absent presets to the default. Runtime values escape the
 * type: removing the reflected `gradient-preset` attribute (e.g. an Angular
 * `[attr.gradient-preset]="null"` binding) drives the prop to null past its
 * field default — without normalization the stop lookup interpolates the
 * literal string "undefined" into CSS and the wash silently disappears.
 */
export declare function normalizeShellGradientPreset(value: string | null | undefined): ShellGradientPreset;
/** Radial wash for a preset — transparent at top-left into the intent stop. `none` returns no image. */
export declare function buildShellRadialGradientForPreset(preset: ShellGradientPreset): string;
/** Build the production shell geometry from an ordered set of design-time stops. */
export declare function buildShellRadialGradientFromStops(stops: readonly ShellGradientStop[]): string;
/** Generic SwatchPicker sections for the fixed shell appearance presets. */
export declare function shellGradientPickerSections(): ShellGradientPickerSection[];