Function decodeImage

tfjs-node/src/image.ts:155–186

(
    content: Uint8Array, channels = 0, dtype = 'int32',
    expandAnimations = true)

 * @doc {heading: 'Operations', subheading: 'Images', namespace: 'node'}
 */
export function decodeImage(
    content: Uint8Array, channels = 0, dtype = 'int32',
    expandAnimations = true): Tensor3D|Tensor4D {
  util.assert(
      dtype === 'int32',
      () => 'decodeImage could only return Tensor of type `int32` for now.');

  const imageType = getImageType(content);

  // The return tensor has dtype uint8, which is not supported in
  // TensorFlow.js, casting it to int32 which is the default dtype for image
  // tensor. If the image is BMP, JPEG or PNG type, expanding the tensors
  // shape so it becomes Tensor4D, which is the default tensor shape for image
  // ([batch,imageHeight,imageWidth, depth]).
  switch (imageType) {
    case ImageType.JPEG:
      return decodeJpeg(content, channels);
    case ImageType.PNG:
      return decodePng(content, channels);
    case ImageType.GIF:
      // If not to expand animations, take first frame of the gif and return
      // as a 3D tensor.
      return tidy(() => {
        const img = decodeGif(content);
        return expandAnimations ? img : img.slice(0, 1).squeeze([0]);
      });
    case ImageType.BMP:
      return decodeBmp(content, channels);
    default:
      return null;
  }
}

/**
 * Encodes an image tensor to JPEG.