@cleerlycode/cornerstone-wado-image-loader/src/webWorker/decodeTask/decodeTask.js

Cornerstone ImageLoader for DICOM WADO-URI

import { initializeJPEG2000 } from './decoders/decodeJPEG2000.js';
import { initializeJPEGLS } from './decoders/decodeJPEGLS.js';
import getMinMax from '../../shared/getMinMax.js';
import decodeImageFrame from './decodeImageFrame.js';

const kTaskType = 'decodeTask';

// flag to ensure codecs are loaded only once
let codecsLoaded = false;

// the configuration object for the decodeTask
let decodeConfig;

/**
 * Function to control loading and initializing the codecs
 */
function loadCodecs() {
  // prevent loading codecs more than once
  if (codecsLoaded) {
    return;
  }

  // Load the codecs
  // console.time('loadCodecs');
  self.importScripts(decodeConfig.codecsPath);
  codecsLoaded = true;
  // console.timeEnd('loadCodecs');

  // Initialize the codecs
  if (decodeConfig.initializeCodecsOnStartup) {
    // console.time('initializeCodecs');
    initializeJPEG2000(decodeConfig);
    initializeJPEGLS(decodeConfig);
    // console.timeEnd('initializeCodecs');
  }
}

/**
 * Task initialization function
 * @param {Object} config The web worker manager `taskConfiguration` field.
 */
function initialize(config) {
  decodeConfig = config[kTaskType] || {};
  if (decodeConfig.loadCodecsOnStartup) {
    loadCodecs();
  }
}

function calculateMinMax(imageFrame) {
  const minMax = getMinMax(imageFrame.pixelData);

  if (decodeConfig.strict === true) {
    if (imageFrame.smallestPixelValue !== minMax.min) {
      console.warn(
        'Image smallestPixelValue tag is incorrect. Rendering performance will suffer considerably.'
      );
    }

    if (imageFrame.largestPixelValue !== minMax.max) {
      console.warn(
        'Image largestPixelValue tag is incorrect. Rendering performance will suffer considerably.'
      );
    }
  } else {
    imageFrame.smallestPixelValue = minMax.min;
    imageFrame.largestPixelValue = minMax.max;
  }
}

/**
 * Task handler function
 */
function handler({ data }, doneCallback) {
  // Load the codecs if they aren't already loaded
  loadCodecs();

  const imageFrame = data.imageFrame;

  // convert pixel data from ArrayBuffer to Uint8Array since web workers support passing ArrayBuffers but
  // not typed arrays
  const pixelData = new Uint8Array(data.pixelData);

  decodeImageFrame(
    imageFrame,
    data.transferSyntax,
    pixelData,
    decodeConfig,
    data.options
  );

  if (!imageFrame.pixelData) {
    throw new Error(
      'decodeTask: imageFrame.pixelData is undefined after decoding'
    );
  }

  calculateMinMax(imageFrame);

  // convert from TypedArray to ArrayBuffer since web workers support passing ArrayBuffers but not
  // typed arrays
  imageFrame.pixelData = imageFrame.pixelData.buffer;

  // invoke the callback with our result and pass the pixelData in the transferList to move it to
  // UI thread without making a copy
  doneCallback(imageFrame, [imageFrame.pixelData]);
}

export default {
  taskType: kTaskType,
  handler,
  initialize
};