@colorhythm/libraw-wasm

TypeScript bindings for LibRaw, compiled to WebAssembly for browser and Node.js camera-raw decoding. Colorhythm maintains this fork for applications that need direct, analysis-oriented access to sensor data—not only a rendered RGB image.

The package is intentionally low-level. It can expose the stored sensor buffer, visible image geometry, color-filter facts, camera characterization, black and saturation levels, embedded metadata, thumbnails, and LibRaw's processed output. Heavy decoding and pixel statistics should normally run in a Worker.

What Colorhythm adds

This fork preserves the original API and adds surfaces needed for browser-side camera-raw analysis:

• Stored and visible geometry, including margins, orientation, pixel aspect, and row pitch
• CFA and Foveon source facts, plus 16-bit one-, three-, and four-component buffers
• Camera matrices, channel descriptions, and white-balance multipliers
• Rawpy-compatible adjusted black levels and reported per-channel linear maxima
• Processing setters for half_size and use_camera_wb
• Typed LibRawError diagnostics with stable numeric LibRaw error codes
• LibRaw's X3F decoder compiled into the WebAssembly build

Install

npm install @colorhythm/libraw-wasm

The generated module loads libraw.wasm beside itself through import.meta.url in Node.js and compatible bundlers. The WebAssembly binary is also exported as @colorhythm/libraw-wasm/libraw.wasm for applications with a custom asset pipeline.

Inspect a camera-raw file

import { LibRaw } from "@colorhythm/libraw-wasm";

async function inspectCameraRaw(file: File) {
    await LibRaw.initialize();

    const decoder = new LibRaw();
    await decoder.waitUntilReady();

    try {
        decoder.open(await file.arrayBuffer());
        decoder.unpack();

        const source =
            decoder.getRawImage() ??
            decoder.getColor3Image() ??
            decoder.getColor4Image();

        if (source === null) {
            throw new Error("LibRaw did not expose an unpacked source buffer");
        }

        const camera = decoder.getIParams();

        return {
            blackLevels: [0, 1, 2, 3].map((index) =>
                decoder.getBlackLevel(index),
            ),
            camera: `${camera.normalized_make} ${camera.normalized_model}`,
            geometry: {
                activeHeight: decoder.getActiveHeight(),
                activeWidth: decoder.getActiveWidth(),
                marginLeft: decoder.getLeftMargin(),
                marginTop: decoder.getTopMargin(),
                storedHeight: decoder.getRawHeight(),
                storedWidth: decoder.getRawWidth(),
            },
            sourceSamples: source.length,
        };
    } finally {
        decoder.dispose();
    }
}

getRawImage(), getColor3Image(), and getColor4Image() return owned Uint16Array copies after unpack(). They remain valid after another decode, recycle(), WebAssembly memory growth, or dispose(). A method returns null when LibRaw does not expose that source layout for the file. The current binding does not expose LibRaw's floating-point source buffers.

1.1.0 compatibility note

Version 1.1.0 corrects the source-pixel return contract introduced in 1.0.0. The TypeScript return type is Uint16Array | null, each non-null array has the exact unpacked length without row padding, and every array owns its storage. Code that assumed the earlier non-null type should select the available source layout explicitly, as in the example above.

Error handling

LibRaw failures throw LibRawError, which preserves the numeric LibRaw error code alongside its diagnostic message:

import { LibRawError } from "@colorhythm/libraw-wasm";

try {
    decoder.open(buffer);
} catch (error) {
    if (error instanceof LibRawError) {
        console.error(error.code, error.message);
    }
    throw error;
}

Analysis API

Area	Methods	Notes
Geometry	getActiveHeight(), getActiveWidth(), getRawHeight(), getRawWidth(), getRawPitch(), margin getters, getFlip(), getPixelAspect()	Raw dimensions describe stored data; LibRaw's visible dimensions and margins locate the image area. These values are not necessarily the literal DNG ActiveArea. Pitch is measured in bytes.
Source layout	getColors(), getCdesc(), getFilters(), getIsFoveon(), color()	Describes CFA and multi-channel source organization. getCdesc() returns a character code.
Source pixels	getRawImage(), getColor3Image(), getColor4Image()	Returns the unpacked 16-bit source buffer that LibRaw exposes for the file.
Levels	getBlackLevel(), getLinearMax(), getColorMaximum(), getDataMaximum()	Exposes adjusted per-channel black levels, per-channel linear maxima, and LibRaw's common and observed maxima. A per-channel linear maximum can be 0 when the file does not provide one.
Characterization	getCamMul(), getPreMul(), getCamXyz(), getCmatrix(), getRgbCam()	Exposes camera white-balance multipliers and numeric color matrices.
Descriptive metadata	getIParams(), getImgOther(), getLensInfo(), getMakernotes(), getShootingInfo()	Reads LibRaw's typed metadata structures. Use a dedicated metadata parser when complete tag coverage is required.
Thumbnails and rendering	unpackThumb(), dcrawMakeMemThumb(), dcrawProcess(), dcrawMakeMemImage()	Provides embedded previews and LibRaw's processed output path.

Static methods expose the compiled LibRaw version, supported camera count, and camera list:

await LibRaw.initialize();

console.log(LibRaw.version());
console.log(LibRaw.cameraCount());
console.log(LibRaw.cameraList());

Processing policy

Set processing parameters before dcrawProcess(). setHalfSize(1) requests half linear dimensions, while setUseCameraWb(1) requests the camera's as-shot white-balance multipliers. Applications should also choose their output color space explicitly with setOutputColor() rather than inherit an implicit LibRaw default.

The unpacked source path does not call dcrawProcess() and therefore remains appropriate for sensor-native analysis.

Worker use

Camera-raw decoding and full-resolution statistics can consume substantial CPU time and memory. In browser applications, create and use LibRaw inside a dedicated Worker. Transfer the input ArrayBuffer to the Worker, perform analysis there, and return only the summaries or pixel data the interface needs.

Each successful open() keeps its copied input alive until another open(), recycle(), or dispose() releases it. Reuse a decoder for sequential jobs or dispose it when the Worker is finished. Source-pixel getters return owned copies that can be transferred or retained independently.

WebAssembly loading and lifecycle

LibRaw.initialize() is shared within a JavaScript realm, and its first call selects the WebAssembly payload. Supply any custom Response or ArrayBuffer before constructing a decoder:

const response = await fetch("/assets/libraw.wasm");

if (!response.ok) {
    throw new Error(`Unable to load LibRaw WASM: ${response.status}`);
}

await LibRaw.initialize(await response.arrayBuffer());

Passing an ArrayBuffer avoids a dependency on the server's WebAssembly MIME type. Passing a Response enables streaming compilation and requires the server to send application/wasm.

Develop

Clone with submodules, install the workspace, and run the checks:

git clone --recurse-submodules https://github.com/colorhythm/libraw-wasm.git
cd libraw-wasm
corepack enable
pnpm install
pnpm check
pnpm test

Rebuilding the WebAssembly binary requires make and Emscripten. Put emcc and em++ on PATH, set SYSROOT to Emscripten's cache/sysroot directory, then run pnpm build. The repository's build setup action is the executable reference for the supported toolchain.

Lineage and thanks

This is Colorhythm's maintained fork of libraw.wasm by TOMIKAWA Sotaro. His TypeScript bindings and WebAssembly build made browser-side LibRaw practical to extend. Thank you, Sotaro.

LibRaw is developed by LibRaw LLC and its contributors.

License

The TypeScript and WebAssembly wrapper is available under the MIT License. The included LibRaw source is available under either LGPL 2.1 or CDDL 1.0. See LibRaw's copyright and notices for its included third-party components. The npm tarball includes all three LibRaw files under LibRaw/.