/**
 * Canvas image post-processing shared by every MolVis surface.
 *
 * Trimming transparent margins and re-encoding are the same operations
 * whether the pixels came from the 3D stage's framebuffer or the 2D
 * sketch board, so both engines export images through this module and
 * users get one consistent result. It lives in `core` because the two
 * engines are peers and cannot import each other.
 *
 * Pure canvas work — no molrs, no engine types.
 */
export interface CropOptions {
    padding?: number;
    mimeType?: string;
    quality?: number;
    alphaThreshold?: number;
}
export interface CropBounds {
    x: number;
    y: number;
    width: number;
    height: number;
}
/**
 * Scan RGBA pixel data for the tight bounding box of non-transparent pixels.
 * Returns null when every pixel has alpha <= threshold (nothing was drawn).
 */
export declare function findAlphaBounds(pixels: Uint8ClampedArray, width: number, height: number, alphaThreshold?: number): CropBounds | null;
/**
 * Decode a data URL and re-encode it as the given mime type (no cropping).
 */
export declare function reencodeImage(dataUrl: string, mimeType: string, quality?: number): Promise<string>;
/**
 * Crop a data URL to the explicit pixel bounds and re-encode. Bounds are
 * clamped to the image extent; empty intersection throws.
 */
export declare function cropToRect(dataUrl: string, bounds: CropBounds, mimeType?: string, quality?: number): Promise<string>;
/**
 * Decode a data URL, scan its alpha channel for drawn content, crop to the tight
 * bounds (with optional padding), and re-encode to the requested mime type.
 *
 * Returns the source data URL unchanged if the image is fully transparent.
 * The input must have an alpha channel (PNG from a transparent-background render).
 */
export declare function cropToContent(dataUrl: string, options?: CropOptions): Promise<string>;