def _compute_targets(ex_rois, gt_rois):
    """Compute bounding-box regression targets for an image. The targets are scale invariance"""

    ex_widths = ex_rois[:, 2] - ex_rois[:, 0] + cfg.EPS
    ex_heights = ex_rois[:, 3] - ex_rois[:, 1] + cfg.EPS
    ex_ctr_x = ex_rois[:, 0] + 0.5 * ex_widths
    ex_ctr_y = ex_rois[:, 1] + 0.5 * ex_heights

    gt_widths = gt_rois[:, 2] - gt_rois[:, 0] + cfg.EPS
    gt_heights = gt_rois[:, 3] - gt_rois[:, 1] + cfg.EPS
    gt_ctr_x = gt_rois[:, 0] + 0.5 * gt_widths
    gt_ctr_y = gt_rois[:, 1] + 0.5 * gt_heights

    targets_dx = (gt_ctr_x - ex_ctr_x) / ex_widths
    targets_dy = (gt_ctr_y - ex_ctr_y) / ex_heights
    targets_dw = np.log(gt_widths / ex_widths)
    targets_dh = np.log(gt_heights / ex_heights)

    targets = np.zeros((ex_rois.shape[0], 4), dtype=np.float32)
    targets[:, 0] = targets_dx
    targets[:, 1] = targets_dy
    targets[:, 2] = targets_dw
    targets[:, 3] = targets_dh
    return targets
Compute bounding-box regression targets for an image. The targets are scale invariance
lib/gt_data_layer/roidb.py