Function decodeJpeg

tfjs-react-native/src/decode_image.ts:34–55

(
    contents: Uint8Array, channels: 0|1|3 = 3)

 * @doc {heading: 'Media', subheading: 'Images'}
 */
export function decodeJpeg(
    contents: Uint8Array, channels: 0|1|3 = 3): Tensor3D {
  util.assert(
      getImageType(contents) === ImageType.JPEG,
      () => 'The passed contents are not a valid JPEG image');
  util.assert(
      channels === 3, () => 'Only 3 channels is supported at this time');
  const {width, height, data} = jpeg.decode(contents, {useTArray: true});
  // Drop the alpha channel info because jpeg.decode always returns a typedArray
  // with 255
  const buffer = new Uint8Array(width * height * 3);
  let offset = 0;  // offset into original data
  for (let i = 0; i < buffer.length; i += 3) {
    buffer[i] = data[offset];
    buffer[i + 1] = data[offset + 1];
    buffer[i + 2] = data[offset + 2];

    offset += 4;
  }

  return tensor3d(buffer, [height, width, channels]);
}

/**
 * Helper function to get image type based on starting bytes of the image file.