@giro3d/giro3d/utils/imageDecoderWorker.js

A JS/WebGL framework for 3D geospatial data visualization

import { createErrorResponse } from './WorkerPool';

// Redeclare those constants to avoid importing them from three.js, since
// that would have a huge impact on bundling this file in an inlined worker,
// because three.js is notoriously un-tree-shakeable.
// (Importing types from three.js is fine, however).
const UnsignedByteType = 1009;
const FloatType = 1015;
export const OPAQUE_BYTE = 255;
export const OPAQUE_FLOAT = 1.0;
export const TRANSPARENT = 0;
export const DEFAULT_NODATA = 0;
export function getTypedArrayType(array) {
  if (array instanceof Float32Array) {
    return 'Float32Array';
  }
  if (array instanceof Float64Array) {
    return 'Float64Array';
  }
  if (array instanceof Uint32Array) {
    return 'Uint32Array';
  }
  if (array instanceof Uint16Array) {
    return 'Uint16Array';
  }
  if (array instanceof Int32Array) {
    return 'Int32Array';
  }
  if (array instanceof Int16Array) {
    return 'Int16Array';
  }
  if (array instanceof Uint8Array) {
    return 'Uint8Array';
  }
  if (array instanceof Int8Array) {
    return 'Int8Array';
  }
  if (array instanceof Uint8ClampedArray) {
    return 'Uint8ClampedArray';
  }
  throw new Error('unsupported type');
}
export function createTypedArrayFromBuffer(buf, type) {
  // Case 1: a texture data type
  if (typeof type === 'number') {
    switch (type) {
      case UnsignedByteType:
        return new Uint8ClampedArray(buf);
      case FloatType:
        return new Float32Array(buf);
    }
  } else {
    // Case 2: a typed array type
    switch (type) {
      case 'Float32Array':
        return new Float32Array(buf);
      case 'Float64Array':
        return new Float64Array(buf);
      case 'Uint8ClampedArray':
        return new Uint8ClampedArray(buf);
      case 'Uint8Array':
        return new Uint8Array(buf);
      case 'Uint16Array':
        return new Uint16Array(buf);
      case 'Uint32Array':
        return new Uint32Array(buf);
      case 'Int8Array':
        return new Int8Array(buf);
      case 'Int16Array':
        return new Int16Array(buf);
      case 'Int32Array':
        return new Int32Array(buf);
    }
  }
  throw new Error('invalid state');
}

// Important note : a lot of code is duplicated to avoid putting
// conditional branches inside loops, as this can severely reduce performance.

// Note: we don't use Number.isNan(x) in the loops as it slows down the loop due to function
// invocation. Instead, we use x !== x, as a NaN is never equal to itself.
export function createPixelBuffer(options) {
  const pixelData = options.input.map(buf => createTypedArrayFromBuffer(buf, options.inputType));
  const opaqueValue = options.opaqueValue;
  let buf;
  if (options.bufferSize && options.dataType) {
    switch (options.dataType) {
      case FloatType:
        buf = new Float32Array(options.bufferSize);
        break;
      case UnsignedByteType:
        buf = new Uint8ClampedArray(options.bufferSize);
        break;
      default:
        throw new Error('unrecognized buffer type: ' + options.dataType);
    }
  } else {
    console.error('missing values');
    throw new Error('missing values');
  }
  let min = +Infinity;
  let max = -Infinity;
  let isTransparent = true;
  if (pixelData.length === 1) {
    const v = pixelData[0];
    const length = v.length;
    for (let i = 0; i < length; i++) {
      const idx = i * 2;
      let value;
      let a;
      const raw = v[i];
      if (raw !== raw || raw === options.nodata) {
        value = DEFAULT_NODATA;
        a = TRANSPARENT;
      } else {
        value = raw;
        a = opaqueValue;
        isTransparent = false;
      }
      min = Math.min(min, value);
      max = Math.max(max, value);
      buf[idx + 0] = value;
      buf[idx + 1] = a;
    }
  }
  if (pixelData.length === 2) {
    const v = pixelData[0];
    const a = pixelData[1];
    const length = v.length;
    for (let i = 0; i < length; i++) {
      const idx = i * 2;
      let value;
      const raw = v[i];
      const alpha = a[i];
      if (raw !== raw || raw === options.nodata) {
        value = DEFAULT_NODATA;
      } else {
        value = raw;
      }
      if (alpha > 0) {
        isTransparent = false;
      }
      min = Math.min(min, value);
      max = Math.max(max, value);
      buf[idx + 0] = value;
      buf[idx + 1] = a[i];
    }
  }
  if (pixelData.length === 3) {
    const rChannel = pixelData[0];
    const gChannel = pixelData[1];
    const bChannel = pixelData[2];
    const length = rChannel.length;
    let a;
    for (let i = 0; i < length; i++) {
      const idx = i * 4;
      let r = rChannel[i];
      let g = gChannel[i];
      let b = bChannel[i];
      if ((r !== r || r === options.nodata) && (g !== g || g === options.nodata) && (b !== b || b === options.nodata)) {
        r = DEFAULT_NODATA;
        g = DEFAULT_NODATA;
        b = DEFAULT_NODATA;
        a = TRANSPARENT;
      } else {
        a = opaqueValue;
        isTransparent = false;
      }
      buf[idx + 0] = r;
      buf[idx + 1] = g;
      buf[idx + 2] = b;
      buf[idx + 3] = a;
    }
  }
  if (pixelData.length === 4) {
    const rChannel = pixelData[0];
    const gChannel = pixelData[1];
    const bChannel = pixelData[2];
    const aChannel = pixelData[3];
    const length = rChannel.length;
    for (let i = 0; i < length; i++) {
      const idx = i * 4;
      let r = rChannel[i];
      let g = gChannel[i];
      let b = bChannel[i];
      let a = aChannel[i];
      if ((r !== r || r === options.nodata) && (g !== g || g === options.nodata) && (b !== b || b === options.nodata)) {
        r = DEFAULT_NODATA;
        g = DEFAULT_NODATA;
        b = DEFAULT_NODATA;
        a = TRANSPARENT;
      } else {
        if (a > 0) {
          isTransparent = false;
        }
      }
      buf[idx + 0] = r;
      buf[idx + 1] = g;
      buf[idx + 2] = b;
      buf[idx + 3] = a;
    }
  }
  return {
    buffer: buf.buffer,
    min,
    max,
    isTransparent
  };
}

// Web worker implementation

onmessage = async function (ev) {
  const message = ev.data;
  try {
    switch (message.type) {
      case 'CreatePixelBuffer':
        {
          const result = createPixelBuffer(message.payload);
          const response = {
            requestId: message.id,
            payload: result
          };
          this.postMessage(response, {
            transfer: [response.payload.buffer]
          });
        }
        break;
      case 'CreateImageBitmap':
        {
          const blob = new Blob([message.payload.buffer]);
          const bitmap = await createImageBitmap(blob, message.payload.options);
          const response = {
            requestId: message.id,
            payload: bitmap
          };
          this.postMessage(response, {
            transfer: [bitmap]
          });
        }
        break;
    }
  } catch (err) {
    this.postMessage(createErrorResponse(message.id, err));
  }
};