webWorker/decodeTask.js

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

// the configuration object for the decodeTask
let decodeConfig;

/**
 * Function to control loading and initializing the codecs
 * @param config
 */
function loadCodecs(config) {
  // Initialize the codecs
  if (config.decodeTask.initializeCodecsOnStartup) {
    console.time('initializeCodecs');
    initializeJPEG2000(config.decodeTask);
    initializeJPEGLS(config.decodeTask);
    console.timeEnd('initializeCodecs');
  }
}

/**
 * Task initialization function
 */
function initialize(config) {
  decodeConfig = config;

  loadCodecs(config);
}

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

  const strict =
    decodeConfig && decodeConfig.decodeTask && decodeConfig.decodeTask.strict;

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

  // TODO switch to promise
  function finishedCallback(imageFrame) {
    if (!imageFrame.pixelData) {
      throw new Error(
        'decodeTask: imageFrame.pixelData is undefined after decoding'
      );
    }

    calculateMinMax(imageFrame, strict);

    // 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

    // ONLY USING setTIMEOUT for TESTING>.. REMOVE THIS
    // setTimeout(() => {
    doneCallback(imageFrame, [imageFrame.pixelData]);
    // }, 100);
  }

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

export default {
  taskType: 'decodeTask',
  handler,
  initialize,
};