问在Tensorflow对象检测API的配置文件中，“keep_aspect_ratio_resizer{”的功能是什么？

EN

// Configuration proto for image resizer that keeps aspect ratio.
message KeepAspectRatioResizer {
  // Desired size of the smaller image dimension in pixels.
  optional int32 min_dimension = 1 [default = 600];

  // Desired size of the larger image dimension in pixels.
  optional int32 max_dimension = 2 [default = 1024];

  // Desired method when resizing image.
  optional ResizeType resize_method = 3 [default = BILINEAR];

  // Whether to pad the image with zeros so the output spatial size is
  // [max_dimension, max_dimension]. Note that the zeros are padded to the
  // bottom and the right of the resized image.
  optional bool pad_to_max_dimension = 4 [default = false];

  // Whether to also resize the image channels from 3 to 1 (RGB to grayscale).
  optional bool convert_to_grayscale = 5 [default = false];

  // Per-channel pad value. This is only used when pad_to_max_dimension is True.
  // If unspecified, a default pad value of 0 is applied to all channels.
  repeated float per_channel_pad_value = 6;
}