/** One decoded bitmap: chunky 8-bit samples, plus alpha when the file carries it. */
export interface DecodedBmp {
    readonly width: number;
    readonly height: number;
    /** Row-major RGB samples, `width * height * 3` long. */
    readonly data: Uint8Array;
    /** One byte per pixel, present only when the file states real transparency. */
    readonly alpha?: Uint8Array;
    /** `biXPelsPerMeter`/`biYPelsPerMeter` turned into pixels per inch. */
    readonly dpiX?: number;
    readonly dpiY?: number;
}
/** Whether these bytes open with the `BM` signature of a bitmap FILE. */
export declare function isBmp(bytes: Uint8Array): boolean;
/**
 * MS-ODRAW §2.2.28 — a `BlipDIB`'s payload is a bitmap without its 14-byte
 * BITMAPFILEHEADER, which the Escher record makes redundant. Put it back.
 *
 * @param dib The bytes from the DIB header onwards.
 * @returns A complete BMP file, or `undefined` when the header does not read
 *          as a bitmap at all.
 */
export declare function dibToBmp(dib: Uint8Array): Uint8Array | undefined;
/**
 * Decode a Windows bitmap into 8-bit RGB samples.
 *
 * @param bytes A complete BMP file (`BM` signature included).
 * @returns The samples, their size and any alpha channel.
 * @throws Error when the file is malformed, or carries a bitmap this does not
 *         read — a JPEG or PNG smuggled inside a DIB (`BI_JPEG`/`BI_PNG`),
 *         which is a whole other file wearing a bitmap header.
 */
export declare function decodeBmp(bytes: Uint8Array): DecodedBmp;