/**
 * Images, which until now were invisible to every part of this.
 *
 * THE HOLE. `mapBlocks` visits a block only when `typeof block.text ===
 * 'string'`, so an image block was never classified, never compressed, never
 * deduplicated and never even counted. That is not a small omission: an
 * Anthropic image costs roughly `width * height / 750` tokens, so one
 * 1456x816 screenshot is about 1,585 tokens -- more than the entire knowledge
 * block -- and it is re-sent as conversation history on every subsequent turn
 * for the rest of the session.
 *
 * A BROWSER-DRIVING AGENT SENDS THE SAME SCREENSHOT REPEATEDLY, and that is
 * the case worth catching. Take a screenshot, act, take another, compare;
 * navigate back, screenshot again. Identical bytes, paid for each time. Text
 * dedup already handles the analogous case for tool output, and the argument
 * transfers exactly: the referent is inside the same request, so a
 * back-reference cannot miss the way a hash into an external cache can.
 *
 * WHAT IS NOT DONE HERE, and why. Re-encoding or downscaling an image needs a
 * codec, and every usable one is a heavy native dependency -- which is
 * precisely the "incompatible with restricted sandboxes" problem this project
 * exists to avoid having. So resizing is an OPTIONAL hook a caller may supply,
 * and the default is to leave the pixels alone. Dedup and accounting need no
 * dependency at all, and they are where the repeated-screenshot money is.
 *
 * DIMENSIONS ARE READ FROM THE HEADER, not by decoding. PNG puts width and
 * height in the IHDR chunk at a fixed offset; JPEG carries them in the first
 * SOFn marker. Both are a few dozen bytes in, so the cost is parsing a header
 * rather than rasterising an image, and an unrecognised format simply declines
 * to estimate rather than guessing.
 */
/** An image found in a request, with where it was and what it costs. */
export interface ImageBlock {
    /** The base64 payload, which is also its identity. */
    readonly data: string;
    readonly mediaType: string;
    /** Estimated tokens, or null when the header was not recognised. */
    readonly tokens: number | null;
    readonly width: number | null;
    readonly height: number | null;
}
/** Below this an image is not worth a back-reference. */
export declare const MIN_DEDUP_IMAGE_CHARS = 1000;
/** Is this content block an image, in either shape a provider accepts? */
export declare function isImageBlock(block: unknown): boolean;
/**
 * Reads an image's dimensions from its header.
 *
 * Only the first kilobyte is decoded, which is far more than any of these
 * headers needs and avoids materialising a multi-megabyte buffer to read six
 * bytes out of it.
 */
export declare function imageSize(data: string): {
    width: number;
    height: number;
} | null;
/** What one image block costs, as far as we can tell. */
export declare function describeImage(block: unknown): ImageBlock | null;
/** The back-reference that replaces a repeated image. */
export declare function imageBackReference(image: ImageBlock, ordinal: number): string;
export interface ImageDedupResult {
    /** One entry per input block: the replacement, or null to keep as-is. */
    readonly replacements: readonly (string | null)[];
    /** Estimated tokens removed, for reporting. */
    readonly tokensSaved: number;
    /** How many repeats were collapsed. */
    readonly collapsed: number;
}
/**
 * Replaces repeated images with a reference to the copy already in the request.
 *
 * Same rules as text dedup, for the same reasons. The FIRST occurrence is
 * always kept whole because it is what every later reference points at, and an
 * untouchable block -- signed, or behind the cache frontier -- is never
 * rewritten but is still the strongest referent there is.
 *
 * Lossless: the image is still in the request, above, and the reference names
 * which one. There is nothing to look up and nothing to miss.
 */
export declare function dedupImages(blocks: readonly {
    readonly block: unknown;
    readonly touchable: boolean;
}[]): ImageDedupResult;
//# sourceMappingURL=images.d.ts.map