exif

EXIF orientation, metadata, and date-parsing utilities.

What it does

@takazudo/zudo-image-tweaker/exif is a small set of standalone utilities for EXIF-related concerns other modules build on: baking orientation into pixels, stripping metadata, classifying an image's orientation, parsing an EXIF capture date, and filtering a width ladder against a source's own width.

Exports

function parseExifDate(buffer: Buffer | Uint8Array | null | undefined): Date | null;
function bakeOrientation(input: SharpInput): Promise<Buffer>;
function stripExif(input: SharpInput): Promise<Buffer>;
function deriveOrientation(width: number, height: number): Orientation;
function pickVariantWidths(srcWidth: number, widths: number[]): number[];

type Orientation = 'landscape' | 'portrait' | 'square';

SharpInput is sharp's own accepted-input type (string | Buffer | ArrayBuffer | Uint8Array | Uint8ClampedArray).

Parameters

None of these five take an options object — each is a plain function over its input(s).

Export	Parameters	Returns	Effect
`parseExifDate`	`buffer: Buffer \| Uint8Array \| null \| undefined`	`Date \| null`	Finds the first `DateTimeOriginal`/`DateTime`-shaped timestamp in a raw EXIF buffer. `null` when none is found or the buffer is empty/nullish.
`bakeOrientation`	`input: SharpInput`	`Promise<Buffer>`	Physically rotates/flips pixel data to match the EXIF `Orientation` tag, then re-encodes without metadata.
`stripExif`	`input: SharpInput`	`Promise<Buffer>`	Re-encodes with all metadata (EXIF, ICC, XMP, …) removed, without altering pixel orientation.
`deriveOrientation`	`width: number, height: number`	`Orientation`	Classifies a dimension pair as `'landscape'`, `'portrait'`, or `'square'`. Throws on non-finite or non-positive input.
`pickVariantWidths`	`srcWidth: number, widths: number[]`	`number[]`	Filters `widths` down to those `<= srcWidth`, preserving input order. Returns `[]` for a non-finite or non-positive `srcWidth`.

Example

import { readFile } from 'node:fs/promises';
import { bakeOrientation, deriveOrientation, parseExifDate } from '@takazudo/zudo-image-tweaker/exif';

const source = await readFile('./photo.jpg');
const upright = await bakeOrientation(source);
const orientation = deriveOrientation(3024, 4032);
const takenAt = parseExifDate(Buffer.from('2026:03:10 08:15:22'));

console.log(orientation, takenAt?.toISOString(), upright.length);

Caveats

bakeOrientation and stripExif are easy to confuse. bakeOrientation physically rotates pixels to match the orientation flag and drops metadata; stripExif only drops metadata and leaves pixels exactly as stored. Calling stripExif alone on a sideways-stored, EXIF-rotated photo leaves it sideways once nothing downstream auto-orients from EXIF anymore.
parseExifDate treats the timestamp as UTC. EXIF ASCII date tags (DateTimeOriginal/DateTime) are stored as YYYY:MM:DD HH:MM:SS with no time zone — this is an intentional approximation that preserves the wall-clock value, not a true UTC conversion.
parseExifDate rejects out-of-range fields that Date would otherwise silently roll over (e.g. 2024:04:31 would become May 1st via the native Date constructor) — a match on the pattern is not proof of a real calendar date, so the parsed result must round-trip back to the exact fields matched, or it returns null.
pickVariantWidths never upscales — it only ever removes widths larger than the source, never adds or clamps one.