/**
 * File-input helpers used by the editor's file-input flow.
 *
 * These helpers cover three concerns:
 *
 * - Determining whether a `File` selected through the upload control is a
 *   supported image, including the extension fallback when `file.type` is
 *   empty (some operating systems and browsers report an empty MIME type
 *   for known extensions).
 * - Reading the file as a base64 data URL so the result can be routed
 *   through the existing transactional `loadImage` pipeline (and therefore
 *   inherit its rollback behavior on decode/Fabric/timeout failure).
 * - Resetting the file input value after every attempt so selecting the
 *   same file again triggers a fresh `change` event.
 *
 * The helpers do not call `loadImage` themselves; the orchestrator wires
 * them into the file-input change handler. That keeps the public
 * `loadImage` API unchanged beyond `LoadImageOptions`.
 */
/**
 * Supported image extensions and the MIME type each one resolves to.
 *
 * Supported file extensions: `png`, `jpg`/`jpeg`, `webp`, `gif`, `bmp`.
 * GIF and BMP are accepted as static raster input for canvas editing. GIF
 * animation and GIF/BMP source-format preservation are not retained; exports
 * are emitted through the editor's JPEG, PNG, or WebP export options.
 *
 * Keys are lowercase extensions without the leading `.`.
 */
export declare const SUPPORTED_IMAGE_EXTENSIONS: Record<string, string>;
export declare const SUPPORTED_IMAGE_MIME_TYPES: Set<string>;
/**
 * Return true only for image data URLs whose MIME type is accepted by the
 * upload path. This keeps public `loadImage(dataUrl)` validation aligned
 * with file-input validation and rejects unsupported image containers such as
 * SVG before any canvas or lifecycle state is touched.
 *
 * The `data:image/` prefix remains case-sensitive to preserve the previous
 * public no-op contract for non-matching data URL prefixes.
 *
 * @param value - Candidate data URL.
 * @returns True when the data URL carries a supported image MIME type.
 */
export declare function isSupportedImageDataUrl(value: unknown): value is string;
/**
 * Determine whether a `File` is a supported image and return its resolved
 * MIME type, or `null` when it should be rejected.
 *
 * Resolution order:
 *
 * 1. If `file.type` is one of the supported image MIME types, return it
 *    verbatim.
 * 2. If `file.type` is empty, infer the MIME type from the file
 *    extension via {@link SUPPORTED_IMAGE_EXTENSIONS}. This covers the
 *    case where a browser or OS reports `''` for files with a known
 *    extension.
 * 3. Otherwise, return `null` so the caller can skip the load without
 *    mutating editor state.
 *
 * @param file - File selected via the upload control.
 * @returns The resolved MIME type, or `null` when the file is not a
 *          supported image.
 */
export declare function inferImageMimeType(file: File): string | null;
/**
 * Read a `File` as a base64 data URL using `FileReader`.
 *
 * The returned data URL is suitable for the transactional `loadImage`
 * pipeline: on failure the editor's existing
 * rollback bundle restores placeholder visibility, scroll, overflow,
 * `originalImage`, `lastSnapshot`, and the canvas JSON snapshot.
 *
 * @param file - File to read.
 * @returns A promise that resolves to the data URL string, or rejects when
 *          the underlying `FileReader` errors out or returns a non-string
 *          result.
 */
export declare function readFileAsDataUrl(file: File): Promise<string>;
/**
 * Reset a file input element's value so selecting the same file again
 * triggers a fresh `change` event.
 *
 * Some browsers reject programmatic assignment to `input.value` on
 * security grounds; the assignment is wrapped in a `try`/`catch` so the
 * caller never has to special-case those environments. A `null` input is
 * a no-op so callers can pass the result of `document.getElementById`
 * without an extra null check.
 *
 * @param input - File input element, or `null` when the element is not
 *              present in the DOM.
 */
export declare function resetFileInput(input: HTMLInputElement | null): void;
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