@kibeo/loaders.gl-textures/dist/esm/lib/parsers/parse-npy.js

Framework-independent loaders for compressed and super compressed (basis) textures

function systemIsLittleEndian() {
  const a = new Uint32Array([0x12345678]);
  const b = new Uint8Array(a.buffer, a.byteOffset, a.byteLength);
  return !(b[0] === 0x12);
}

const LITTLE_ENDIAN_OS = systemIsLittleEndian();
const DTYPES = {
  u1: Uint8Array,
  i1: Int8Array,
  u2: Uint16Array,
  i2: Int16Array,
  u4: Uint32Array,
  i4: Int32Array,
  f4: Float32Array,
  f8: Float64Array
};
export function parseNPY(arrayBuffer, options) {
  if (!arrayBuffer) {
    return null;
  }

  const view = new DataView(arrayBuffer);
  const {
    header,
    headerEndOffset
  } = parseHeader(view);
  const numpyType = header.descr;
  const ArrayType = DTYPES[numpyType.slice(1, 3)];

  if (!ArrayType) {
    console.warn("Decoding of npy dtype not implemented: ".concat(numpyType));
    return null;
  }

  const nArrayElements = header.shape.reduce((a, b) => a * b);
  const arrayByteLength = nArrayElements * ArrayType.BYTES_PER_ELEMENT;
  const data = new ArrayType(arrayBuffer.slice(headerEndOffset, headerEndOffset + arrayByteLength));

  if (numpyType[0] === '>' && LITTLE_ENDIAN_OS || numpyType[0] === '<' && !LITTLE_ENDIAN_OS) {
    console.warn('Data is wrong endianness, byte swapping not yet implemented.');
  }

  return {
    data,
    header
  };
}

function parseHeader(view) {
  const majorVersion = view.getUint8(6);
  let offset = 8;
  let headerLength;

  if (majorVersion >= 2) {
    headerLength = view.getUint32(8, true);
    offset += 4;
  } else {
    headerLength = view.getUint16(8, true);
    offset += 2;
  }

  const encoding = majorVersion <= 2 ? 'latin1' : 'utf-8';
  const decoder = new TextDecoder(encoding);
  const headerArray = new Uint8Array(view.buffer, offset, headerLength);
  const headerText = decoder.decode(headerArray);
  offset += headerLength;
  const header = JSON.parse(headerText.replace(/'/g, '"').replace('False', 'false').replace('(', '[').replace(/,*\),*/g, ']'));
  return {
    header,
    headerEndOffset: offset
  };
}
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