dicom-codec

DICOM codecs for JavaScript, with browser and Node.js support.

Features (v1.0.1)

Next releases planning

v0.0.11: support for LibjpegTurbo12Bit v.0.0.12 support for encoding options. v1.0.0: support for browser (dynamic loading included) and node.

Future releases

• RleLossless to be js/wasm based.
• Support for the rest of operations for existing codecs.
• Support for the rest of the DICOM transfer syntaxes.

Building

# Restore packages
pnpm install

# Build
pnpm run build

How to use

Commonjs

const dicomCodec = require('@cornerstonejs/dicom-codec');
....
const imageFrame = ....// see API
const imageInfo = {} // add here image information (see API)
const result = await dicomCodec.transcode(imageFrame, imageInfo, sourceTransferSyntaxUID, targetTransferSyntaxUID);
const pixelData = dicomCodec.getPixelData(result.imageFrame, result.imageInfo);

ES6

import dicomCodec from '@cornerstonejs/dicom-codec';
...
const imageFrame = ....// see API
const imageInfo = {} // add here image information (see API)
const result = await dicomCodec.transcode(imageFrame, imageInfo, sourceTransferSyntaxUID, targetTransferSyntaxUID);
const pixelData = dicomCodec.getPixelData(result.imageFrame, result.imageInfo);

API

decode

async function that decodes an image

Parameters (It does not mutate any param):

• compressedImageFrame - TypedArray with the compressed image frame bytes.
• imageInfo - Object
  • rows - Number with the image rows/height.
  • columns - Number with the image columns/width.
  • bitsAllocated - Number with bits per pixel sample.
  • samplesPerPixel - Number with number of components per pixel.
  • signed - Boolean true if pixel data is signed, false if unsigned.
• sourceTransferSyntaxUID - String with the transfer syntax uid of the compressed image frame

Returns:

• Object
  • imageFrame - TypedArray with the uncompressed image frame bytes (Mostly codecs returns Uint8Array, but Uint16Array, Int16Array can be seen)
  • imageInfo - Object
    • rows - Number with the image rows/height.
    • columns - Number with the image columns/width.
    • bitsAllocated - Number with bits per pixel sample.
    • samplesPerPixel - Number with number of components per pixel.
    • signed - Boolean true if pixel data is signed, false if unsigned.
    • there are also some other codec properties.

Decode does not occur if there is no codec for sourceTransferSyntaxUID or related codec's transferSyntaxUID refers to uncompressed.

encode

async function that encodes an image

Parameters (It does not mutate any param):

• imageFrame - TypedArray with the uncompressed image frame bytes
• imageInfo - Object
  • rows - Number with the image rows/height.
  • columns - Number with the image columns/width.
  • bitsAllocated - Number with bits per pixel sample.
  • samplesPerPixel - Number with number of components per pixel.
  • signed - Boolean true if pixel data is signed, false if unsigned.
• targetTransferSyntaxUID - String with the transfer syntax uid to encode the image frame as
• encodeOptions - Object - contents specific to each codec (see below) (v>=0.0.12)

Returns:

• Object
  • imageFrame - TypedArray with the image frame bytes (Mostly codecs returns Uint8Array, but Uint16Array, Int16Array can be seen)
  • imageInfo - Object
    • rows - Number with the image rows/height.
    • columns - Number with the image columns/width.
    • bitsAllocated - Number with bits per pixel sample.
    • samplesPerPixel - Number with number of components per pixel.
    • signed - Boolean true if pixel data is signed, false if unsigned.
    • there are also some other codec properties.
  • processInfo - Object
    • duration - Number with process'duration in ms.

Encode does not occur if there is no codec for targetTransferSyntaxUID or related codec's transferSyntaxUID refers to uncompressed.

transcode

async function that transcodes an image (decodes and then encodes)

Parameters (It does not mutate any param):

• imageFrame - TypedArray with the image frame bytes
• imageInfo - Object
  • rows - Number with the image rows/height.
  • columns - Number with the image columns/width.
  • bitsAllocated - Number with bits per pixel sample.
  • samplesPerPixel - Number with number of components per pixel.
  • signed - Boolean true if pixel data is signed, false if unsigned.
• sourceTransferSyntaxUID - String with the transfer syntax uid of the compressed.
• targetTransferSyntaxUID - String with the transfer syntax uid to encode the image frame as.
• encodeOptions - Object - contents specific to each codec (see below) (v>=0.0.12)

Returns:

• Object
  • imageFrame - TypedArray with the uncompressed image frame bytes (Mostly codecs returns Uint8Array, but Uint16Array, Int16Array can be seen)
  • imageInfo - Object
    • rows - Number with the image rows/height.
    • columns - Number with the image columns/width.
    • bitsAllocated - Number with bits per pixel sample.
    • samplesPerPixel - Number with number of components per pixel.
    • signed - Boolean true if pixel data is signed, false if unsigned.
    • there are also some other codec properties.
  • processInfo - Object
    • duration - Number with process'duration in ms.

Transcode might not occur depending on transferSyntaxUID's params (see above).

getPixelData

function that returns formatted imageFrame based on imageInfo Some of codecs might have specific rules for pixelData based on imageInfo.

Parameters (It does not mutate any param):

• imageFrame - TypedArray with the uncompressed image frame bytes
• imageInfo - Object
  • rows - Number with the image rows/height.
  • columns - Number with the image columns/width.
  • bitsAllocated - Number with bits per pixel sample.
  • samplesPerPixel - Number with number of components per pixel.
  • signed - Boolean true if pixel data is signed, false if unsigned.

Returns:

• Object
  • imageFrame - TypedArray with the image frame bytes (Mostly codecs returns Uint8Array, but Uint16Array, Int16Array can be seen). Each codec might treat this differently based on imageInfo.

setConfig

function that set up dicom-codec configuration properties Parameters (It does not mutate any param ):

• options - Object
  • verbose - Boolean true if dicom-codec should be verbose, false otherwise.

TransferSyntax Specific Encoding Options

JPEG XL

Transfer syntax 1.2.840.10008.1.2.4.110 always uses lossless encoding. Transfer syntax 1.2.840.10008.1.2.4.111 supports decoding only because the pixel encoder does not create JPEG reconstruction data.

Transfer syntax 1.2.840.10008.1.2.4.112 accepts these encoding options:

• lossless: Boolean, defaults to true.
• distance: Butteraugli distance from 0 to 25 for lossy encoding. Defaults to 1.0 — cjxl's default, "visually lossless" — when lossless is false and no distance is given. Do not rely on libjxl's own default of 0: it reaches distance 0 through VarDCT rather than the modular path, which is larger than a real lossless encode and still not lossless.
• effort: Integer from 1 to 9.
• decodingSpeed: Integer from 0 to 4.

Signed pixel data

JPEG XL has no signed sample type — JxlDataType is unsigned integer or float — so Pixel Representation cannot be carried in the codestream. PS3.5 8.2.15 allows Pixel Representation to be 1 for monochrome JPEG XL images but defines no mechanism for it, so the mapping is a convention. This library uses a different one per transfer syntax, and applies it automatically:

.112 needs the shift because as unsigned, a CT frame's [-2048, 1704] becomes [0, 1704] plus [63488, 65535], and lossy coding smears across the gap: 2211 HU of maximum error at distance 1.0 without it. The shift is applied to every signed .112 frame, lossless option or not, so that decoding can invert it knowing only the transfer syntax.

Two consequences worth knowing:

• A signed frame produces different bytes under .110 and .112. Both decode back to the same pixels here, but a .112 stream read by a decoder that assumes two's complement is off by 2^(BitsStored-1). Nothing in the standard distinguishes the conventions.
• Butteraugli distance is relative to the full BitsAllocated range. CT occupies roughly 6% of a 16-bit range, so distance 1.0 still permits hundreds of HU of error. Use a small distance, or .110, when HU fidelity matters.

The same limitation applies to JPEG-LS, which also has no sign flag; this library only ever encodes JPEG-LS losslessly for that reason.

Testing

pnpm run test   # run vitest dispatch + integration tests

The integration tests require every underlying wasm codec's dist/ to be built locally; otherwise they skip cleanly. CI builds everything first.