target_assigner.py 文件源码

def _create_regression_targets(self, anchors, groundtruth_boxes, match):
    """Returns a regression target for each anchor.

    Args:
      anchors: a BoxList representing N anchors
      groundtruth_boxes: a BoxList representing M groundtruth_boxes
      match: a matcher.Match object

    Returns:
      reg_targets: a float32 tensor with shape [N, box_code_dimension]
    """
    matched_anchor_indices = match.matched_column_indices()
    unmatched_ignored_anchor_indices = (match.
                                        unmatched_or_ignored_column_indices())
    matched_gt_indices = match.matched_row_indices()
    matched_anchors = box_list_ops.gather(anchors,
                                          matched_anchor_indices)
    matched_gt_boxes = box_list_ops.gather(groundtruth_boxes,
                                           matched_gt_indices)
    matched_reg_targets = self._box_coder.encode(matched_gt_boxes,
                                                 matched_anchors)
    unmatched_ignored_reg_targets = tf.tile(
        self._default_regression_target(),
        tf.stack([tf.size(unmatched_ignored_anchor_indices), 1]))
    reg_targets = tf.dynamic_stitch(
        [matched_anchor_indices, unmatched_ignored_anchor_indices],
        [matched_reg_targets, unmatched_ignored_reg_targets])
    # TODO: summarize the number of matches on average.
    return reg_targets