import numpy as np
import numpy as xp

import six
from six import __init__


def loc2bbox(src_bbox, loc):
    """Decode bounding boxes from bounding box offsets and scales.

    Given bounding box offsets and scales computed by
    :meth:`bbox2loc`, this function decodes the representation to
    coordinates in 2D image coordinates.

    Given scales and offsets :math:`t_y, t_x, t_h, t_w` and a bounding
    box whose center is :math:`(y, x) = p_y, p_x` and size :math:`p_h, p_w`,
    the decoded bounding box‘s center :math:`\\hat{g}_y`, :math:`\\hat{g}_x`
    and size :math:`\\hat{g}_h`, :math:`\\hat{g}_w` are calculated
    by the following formulas.

    * :math:`\\hat{g}_y = p_h t_y + p_y`
    * :math:`\\hat{g}_x = p_w t_x + p_x`
    * :math:`\\hat{g}_h = p_h \\exp(t_h)`
    * :math:`\\hat{g}_w = p_w \\exp(t_w)`

    The decoding formulas are used in works such as R-CNN [#]_.

    The output is same type as the type of the inputs.

    .. [#] Ross Girshick, Jeff Donahue, Trevor Darrell, Jitendra Malik.     Rich feature hierarchies for accurate object detection and semantic     segmentation. CVPR 2014.

    Args:
        src_bbox (array): A coordinates of bounding boxes.
            Its shape is :math:`(R, 4)`. These coordinates are
            :math:`p_{ymin}, p_{xmin}, p_{ymax}, p_{xmax}`.
        loc (array): An array with offsets and scales.
            The shapes of :obj:`src_bbox` and :obj:`loc` should be same.
            This contains values :math:`t_y, t_x, t_h, t_w`.

    Returns:
        array:
        Decoded bounding box coordinates. Its shape is :math:`(R, 4)`.         The second axis contains four values         :math:`\\hat{g}_{ymin}, \\hat{g}_{xmin},
        \\hat{g}_{ymax}, \\hat{g}_{xmax}`.

    """

    if src_bbox.shape[0] == 0:
        return xp.zeros((0, 4), dtype=loc.dtype)

    src_bbox = src_bbox.astype(src_bbox.dtype, copy=False)

    src_height = src_bbox[:, 2] - src_bbox[:, 0]
    src_width = src_bbox[:, 3] - src_bbox[:, 1]
    src_ctr_y = src_bbox[:, 0] + 0.5 * src_height
    src_ctr_x = src_bbox[:, 1] + 0.5 * src_width

    dy = loc[:, 0::4]
    dx = loc[:, 1::4]
    dh = loc[:, 2::4]
    dw = loc[:, 3::4]

    ctr_y = dy * src_height[:, xp.newaxis] + src_ctr_y[:, xp.newaxis]
    ctr_x = dx * src_width[:, xp.newaxis] + src_ctr_x[:, xp.newaxis]
    h = xp.exp(dh) * src_height[:, xp.newaxis]
    w = xp.exp(dw) * src_width[:, xp.newaxis]

    dst_bbox = xp.zeros(loc.shape, dtype=loc.dtype)
    dst_bbox[:, 0::4] = ctr_y - 0.5 * h
    dst_bbox[:, 1::4] = ctr_x - 0.5 * w
    dst_bbox[:, 2::4] = ctr_y + 0.5 * h
    dst_bbox[:, 3::4] = ctr_x + 0.5 * w

    return dst_bbox


def bbox2loc(src_bbox, dst_bbox):
    """Encodes the source and the destination bounding boxes to "loc".

    Given bounding boxes, this function computes offsets and scales
    to match the source bounding boxes to the target bounding boxes.
    Mathematcially, given a bounding box whose center is
    :math:`(y, x) = p_y, p_x` and
    size :math:`p_h, p_w` and the target bounding box whose center is
    :math:`g_y, g_x` and size :math:`g_h, g_w`, the offsets and scales
    :math:`t_y, t_x, t_h, t_w` can be computed by the following formulas.

    * :math:`t_y = \\frac{(g_y - p_y)} {p_h}`
    * :math:`t_x = \\frac{(g_x - p_x)} {p_w}`
    * :math:`t_h = \\log(\\frac{g_h} {p_h})`
    * :math:`t_w = \\log(\\frac{g_w} {p_w})`

    The output is same type as the type of the inputs.
    The encoding formulas are used in works such as R-CNN [#]_.

    .. [#] Ross Girshick, Jeff Donahue, Trevor Darrell, Jitendra Malik.     Rich feature hierarchies for accurate object detection and semantic     segmentation. CVPR 2014.

    Args:
        src_bbox (array): An image coordinate array whose shape is
            :math:`(R, 4)`. :math:`R` is the number of bounding boxes.
            These coordinates are
            :math:`p_{ymin}, p_{xmin}, p_{ymax}, p_{xmax}`.
        dst_bbox (array): An image coordinate array whose shape is
            :math:`(R, 4)`.
            These coordinates are
            :math:`g_{ymin}, g_{xmin}, g_{ymax}, g_{xmax}`.

    Returns:
        array:
        Bounding box offsets and scales from :obj:`src_bbox`         to :obj:`dst_bbox`.         This has shape :math:`(R, 4)`.
        The second axis contains four values :math:`t_y, t_x, t_h, t_w`.

    """

    height = src_bbox[:, 2] - src_bbox[:, 0]
    width = src_bbox[:, 3] - src_bbox[:, 1]
    ctr_y = src_bbox[:, 0] + 0.5 * height
    ctr_x = src_bbox[:, 1] + 0.5 * width

    base_height = dst_bbox[:, 2] - dst_bbox[:, 0]
    base_width = dst_bbox[:, 3] - dst_bbox[:, 1]
    base_ctr_y = dst_bbox[:, 0] + 0.5 * base_height
    base_ctr_x = dst_bbox[:, 1] + 0.5 * base_width

    eps = xp.finfo(height.dtype).eps
    height = xp.maximum(height, eps)
    width = xp.maximum(width, eps)

    dy = (base_ctr_y - ctr_y) / height
    dx = (base_ctr_x - ctr_x) / width
    dh = xp.log(base_height / height)
    dw = xp.log(base_width / width)

    loc = xp.vstack((dy, dx, dh, dw)).transpose()
    return loc


def bbox_iou(bbox_a, bbox_b):
    """Calculate the Intersection of Unions (IoUs) between bounding boxes.

    IoU is calculated as a ratio of area of the intersection
    and area of the union.

    This function accepts both :obj:`numpy.ndarray` and :obj:`cupy.ndarray` as
    inputs. Please note that both :obj:`bbox_a` and :obj:`bbox_b` need to be
    same type.
    The output is same type as the type of the inputs.

    Args:
        bbox_a (array): An array whose shape is :math:`(N, 4)`.
            :math:`N` is the number of bounding boxes.
            The dtype should be :obj:`numpy.float32`.
        bbox_b (array): An array similar to :obj:`bbox_a`,
            whose shape is :math:`(K, 4)`.
            The dtype should be :obj:`numpy.float32`.

    Returns:
        array:
        An array whose shape is :math:`(N, K)`.         An element at index :math:`(n, k)` contains IoUs between         :math:`n` th bounding box in :obj:`bbox_a` and :math:`k` th bounding         box in :obj:`bbox_b`.

    """
    if bbox_a.shape[1] != 4 or bbox_b.shape[1] != 4:
        raise IndexError

    # top left
    tl = xp.maximum(bbox_a[:, None, :2], bbox_b[:, :2])
    # bottom right
    br = xp.minimum(bbox_a[:, None, 2:], bbox_b[:, 2:])

    area_i = xp.prod(br - tl, axis=2) * (tl < br).all(axis=2)
    area_a = xp.prod(bbox_a[:, 2:] - bbox_a[:, :2], axis=1)
    area_b = xp.prod(bbox_b[:, 2:] - bbox_b[:, :2], axis=1)
    return area_i / (area_a[:, None] + area_b - area_i)


def __test():
    pass


if __name__ == ‘__main__‘:
    __test()


def generate_anchor_base(base_size=16, ratios=[0.5, 1, 2],
                         anchor_scales=[8, 16, 32]):
    """Generate anchor base windows by enumerating aspect ratio and scales.

    Generate anchors that are scaled and modified to the given aspect ratios.
    Area of a scaled anchor is preserved when modifying to the given aspect
    ratio.

    :obj:`R = len(ratios) * len(anchor_scales)` anchors are generated by this
    function.
    The :obj:`i * len(anchor_scales) + j` th anchor corresponds to an anchor
    generated by :obj:`ratios[i]` and :obj:`anchor_scales[j]`.

    For example, if the scale is :math:`8` and the ratio is :math:`0.25`,
    the width and the height of the base window will be stretched by :math:`8`.
    For modifying the anchor to the given aspect ratio,
    the height is halved and the width is doubled.

    Args:
        base_size (number): The width and the height of the reference window.
        ratios (list of floats): This is ratios of width to height of
            the anchors.
        anchor_scales (list of numbers): This is areas of anchors.
            Those areas will be the product of the square of an element in
            :obj:`anchor_scales` and the original area of the reference
            window.

    Returns:
        ~numpy.ndarray:
        An array of shape :math:`(R, 4)`.
        Each element is a set of coordinates of a bounding box.
        The second axis corresponds to
        :math:`(y_{min}, x_{min}, y_{max}, x_{max})` of a bounding box.

    """
    py = base_size / 2.
    px = base_size / 2.

    anchor_base = np.zeros((len(ratios) * len(anchor_scales), 4),
                           dtype=np.float32)
    for i in six.moves.range(len(ratios)):
        for j in six.moves.range(len(anchor_scales)):
            h = base_size * anchor_scales[j] * np.sqrt(ratios[i])
            w = base_size * anchor_scales[j] * np.sqrt(1. / ratios[i])

            index = i * len(anchor_scales) + j
            anchor_base[index, 0] = py - h / 2.
            anchor_base[index, 1] = px - w / 2.
            anchor_base[index, 2] = py + h / 2.
            anchor_base[index, 3] = px + w / 2.
    return anchor_base

import numpy as np
import cupy as cp

from model.utils.bbox_tools import bbox2loc, bbox_iou, loc2bbox
from model.utils.nms import non_maximum_suppression


class ProposalTargetCreator(object):
    """Assign ground truth bounding boxes to given RoIs.

    The :meth:`__call__` of this class generates training targets
    for each object proposal.
    This is used to train Faster RCNN [#]_.

    .. [#] Shaoqing Ren, Kaiming He, Ross Girshick, Jian Sun.     Faster R-CNN: Towards Real-Time Object Detection with     Region Proposal Networks. NIPS 2015.

    Args:
        n_sample (int): The number of sampled regions.
        pos_ratio (float): Fraction of regions that is labeled as a
            foreground.
        pos_iou_thresh (float): IoU threshold for a RoI to be considered as a
            foreground.
        neg_iou_thresh_hi (float): RoI is considered to be the background
            if IoU is in
            [:obj:`neg_iou_thresh_hi`, :obj:`neg_iou_thresh_hi`).
        neg_iou_thresh_lo (float): See above.

    """

    def __init__(self,
                 n_sample=128,
                 pos_ratio=0.25, pos_iou_thresh=0.5,
                 neg_iou_thresh_hi=0.5, neg_iou_thresh_lo=0.0
                 ):
        self.n_sample = n_sample
        self.pos_ratio = pos_ratio
        self.pos_iou_thresh = pos_iou_thresh
        self.neg_iou_thresh_hi = neg_iou_thresh_hi
        self.neg_iou_thresh_lo = neg_iou_thresh_lo  # NOTE: py-faster-rcnn默认的值是0.1

    def __call__(self, roi, bbox, label,
                 loc_normalize_mean=(0., 0., 0., 0.),
                 loc_normalize_std=(0.1, 0.1, 0.2, 0.2)):
        """Assigns ground truth to sampled proposals.

        This function samples total of :obj:`self.n_sample` RoIs
        from the combination of :obj:`roi` and :obj:`bbox`.
        The RoIs are assigned with the ground truth class labels as well as
        bounding box offsets and scales to match the ground truth bounding
        boxes. As many as :obj:`pos_ratio * self.n_sample` RoIs are
        sampled as foregrounds.

        Offsets and scales of bounding boxes are calculated using
        :func:`model.utils.bbox_tools.bbox2loc`.
        Also, types of input arrays and output arrays are same.

        Here are notations.

        * :math:`S` is the total number of sampled RoIs, which equals             :obj:`self.n_sample`.
        * :math:`L` is number of object classes possibly including the             background.

        Args:
            roi (array): Region of Interests (RoIs) from which we sample.
                Its shape is :math:`(R, 4)`
            bbox (array): The coordinates of ground truth bounding boxes.
                Its shape is :math:`(R‘, 4)`.
            label (array): Ground truth bounding box labels. Its shape
                is :math:`(R‘,)`. Its range is :math:`[0, L - 1]`, where
                :math:`L` is the number of foreground classes.
            loc_normalize_mean (tuple of four floats): Mean values to normalize
                coordinates of bouding boxes.
            loc_normalize_std (tupler of four floats): Standard deviation of
                the coordinates of bounding boxes.

        Returns:
            (array, array, array):

            * **sample_roi**: Regions of interests that are sampled.                 Its shape is :math:`(S, 4)`.
            * **gt_roi_loc**: Offsets and scales to match                 the sampled RoIs to the ground truth bounding boxes.                 Its shape is :math:`(S, 4)`.
            * **gt_roi_label**: Labels assigned to sampled RoIs. Its shape is                 :math:`(S,)`. Its range is :math:`[0, L]`. The label with                 value 0 is the background.

        """
        n_bbox, _ = bbox.shape

        roi = np.concatenate((roi, bbox), axis=0)

        pos_roi_per_image = np.round(self.n_sample * self.pos_ratio)
        iou = bbox_iou(roi, bbox)
        gt_assignment = iou.argmax(axis=1)
        max_iou = iou.max(axis=1)
        # Offset range of classes from [0, n_fg_class - 1] to [1, n_fg_class].
        # The label with value 0 is the background.
        gt_roi_label = label[gt_assignment] + 1

        # Select foreground RoIs as those with >= pos_iou_thresh IoU.
        pos_index = np.where(max_iou >= self.pos_iou_thresh)[0]
        pos_roi_per_this_image = int(min(pos_roi_per_image, pos_index.size))
        if pos_index.size > 0:
            pos_index = np.random.choice(
                pos_index, size=pos_roi_per_this_image, replace=False)

        # Select background RoIs as those within
        # [neg_iou_thresh_lo, neg_iou_thresh_hi).
        neg_index = np.where((max_iou < self.neg_iou_thresh_hi) &
                             (max_iou >= self.neg_iou_thresh_lo))[0]
        neg_roi_per_this_image = self.n_sample - pos_roi_per_this_image
        neg_roi_per_this_image = int(min(neg_roi_per_this_image,
                                         neg_index.size))
        if neg_index.size > 0:
            neg_index = np.random.choice(
                neg_index, size=neg_roi_per_this_image, replace=False)

        # The indices that we‘re selecting (both positive and negative).
        keep_index = np.append(pos_index, neg_index)
        gt_roi_label = gt_roi_label[keep_index]
        gt_roi_label[pos_roi_per_this_image:] = 0  # negative labels --> 0
        sample_roi = roi[keep_index]

        # Compute offsets and scales to match sampled RoIs to the GTs.
        gt_roi_loc = bbox2loc(sample_roi, bbox[gt_assignment[keep_index]])
        gt_roi_loc = ((gt_roi_loc - np.array(loc_normalize_mean, np.float32)
                       ) / np.array(loc_normalize_std, np.float32))

        return sample_roi, gt_roi_loc, gt_roi_label


class AnchorTargetCreator(object):
    """Assign the ground truth bounding boxes to anchors.

    Assigns the ground truth bounding boxes to anchors for training Region
    Proposal Networks introduced in Faster R-CNN [#]_.

    Offsets and scales to match anchors to the ground truth are
    calculated using the encoding scheme of
    :func:`model.utils.bbox_tools.bbox2loc`.

    .. [#] Shaoqing Ren, Kaiming He, Ross Girshick, Jian Sun.     Faster R-CNN: Towards Real-Time Object Detection with     Region Proposal Networks. NIPS 2015.

    Args:
        n_sample (int): The number of regions to produce.
        pos_iou_thresh (float): Anchors with IoU above this
            threshold will be assigned as positive.
        neg_iou_thresh (float): Anchors with IoU below this
            threshold will be assigned as negative.
        pos_ratio (float): Ratio of positive regions in the
            sampled regions.

    """

    def __init__(self,
                 n_sample=256,
                 pos_iou_thresh=0.7, neg_iou_thresh=0.3,
                 pos_ratio=0.5):
        self.n_sample = n_sample
        self.pos_iou_thresh = pos_iou_thresh
        self.neg_iou_thresh = neg_iou_thresh
        self.pos_ratio = pos_ratio

    def __call__(self, bbox, anchor, img_size):
        """Assign ground truth supervision to sampled subset of anchors.

        Types of input arrays and output arrays are same.

        Here are notations.

        * :math:`S` is the number of anchors.
        * :math:`R` is the number of bounding boxes.

        Args:
            bbox (array): Coordinates of bounding boxes. Its shape is
                :math:`(R, 4)`.
            anchor (array): Coordinates of anchors. Its shape is
                :math:`(S, 4)`.
            img_size (tuple of ints): A tuple :obj:`H, W`, which
                is a tuple of height and width of an image.

        Returns:
            (array, array):

            #NOTE: it‘s scale not only  offset
            * **loc**: Offsets and scales to match the anchors to                 the ground truth bounding boxes. Its shape is :math:`(S, 4)`.
            * **label**: Labels of anchors with values                 :obj:`(1=positive, 0=negative, -1=ignore)`. Its shape                 is :math:`(S,)`.

        """

        img_H, img_W = img_size

        n_anchor = len(anchor)
        inside_index = _get_inside_index(anchor, img_H, img_W)
        anchor = anchor[inside_index]
        argmax_ious, label = self._create_label(
            inside_index, anchor, bbox)

        # compute bounding box regression targets
        loc = bbox2loc(anchor, bbox[argmax_ious])

        # map up to original set of anchors
        label = _unmap(label, n_anchor, inside_index, fill=-1)
        loc = _unmap(loc, n_anchor, inside_index, fill=0)

        return loc, label

    def _create_label(self, inside_index, anchor, bbox):
        # label: 1 is positive, 0 is negative, -1 is dont care
        label = np.empty((len(inside_index),), dtype=np.int32)
        label.fill(-1)

        argmax_ious, max_ious, gt_argmax_ious =             self._calc_ious(anchor, bbox, inside_index)

        # assign negative labels first so that positive labels can clobber them
        label[max_ious < self.neg_iou_thresh] = 0

        # positive label: for each gt, anchor with highest iou
        label[gt_argmax_ious] = 1

        # positive label: above threshold IOU
        label[max_ious >= self.pos_iou_thresh] = 1

        # subsample positive labels if we have too many
        n_pos = int(self.pos_ratio * self.n_sample)
        pos_index = np.where(label == 1)[0]
        if len(pos_index) > n_pos:
            disable_index = np.random.choice(
                pos_index, size=(len(pos_index) - n_pos), replace=False)
            label[disable_index] = -1

        # subsample negative labels if we have too many
        n_neg = self.n_sample - np.sum(label == 1)
        neg_index = np.where(label == 0)[0]
        if len(neg_index) > n_neg:
            disable_index = np.random.choice(
                neg_index, size=(len(neg_index) - n_neg), replace=False)
            label[disable_index] = -1

        return argmax_ious, label

    def _calc_ious(self, anchor, bbox, inside_index):
        # ious between the anchors and the gt boxes
        ious = bbox_iou(anchor, bbox)
        argmax_ious = ious.argmax(axis=1)
        max_ious = ious[np.arange(len(inside_index)), argmax_ious]
        gt_argmax_ious = ious.argmax(axis=0)
        gt_max_ious = ious[gt_argmax_ious, np.arange(ious.shape[1])]
        gt_argmax_ious = np.where(ious == gt_max_ious)[0]

        return argmax_ious, max_ious, gt_argmax_ious


def _unmap(data, count, index, fill=0):
    # Unmap a subset of item (data) back to the original set of items (of
    # size count)

    if len(data.shape) == 1:
        ret = np.empty((count,), dtype=data.dtype)
        ret.fill(fill)
        ret[index] = data
    else:
        ret = np.empty((count,) + data.shape[1:], dtype=data.dtype)
        ret.fill(fill)
        ret[index, :] = data
    return ret


def _get_inside_index(anchor, H, W):
    # Calc indicies of anchors which are located completely inside of the image
    # whose size is speficied.
    index_inside = np.where(
        (anchor[:, 0] >= 0) &
        (anchor[:, 1] >= 0) &
        (anchor[:, 2] <= H) &
        (anchor[:, 3] <= W)
    )[0]
    return index_inside


class ProposalCreator:
    # unNOTE: I‘ll make it undifferential
    # unTODO: make sure it‘s ok
    # It‘s ok
    """Proposal regions are generated by calling this object.

    The :meth:`__call__` of this object outputs object detection proposals by
    applying estimated bounding box offsets
    to a set of anchors.

    This class takes parameters to control number of bounding boxes to
    pass to NMS and keep after NMS.
    If the paramters are negative, it uses all the bounding boxes supplied
    or keep all the bounding boxes returned by NMS.

    This class is used for Region Proposal Networks introduced in
    Faster R-CNN [#]_.

    .. [#] Shaoqing Ren, Kaiming He, Ross Girshick, Jian Sun.     Faster R-CNN: Towards Real-Time Object Detection with     Region Proposal Networks. NIPS 2015.

    Args:
        nms_thresh (float): Threshold value used when calling NMS.
        n_train_pre_nms (int): Number of top scored bounding boxes
            to keep before passing to NMS in train mode.
        n_train_post_nms (int): Number of top scored bounding boxes
            to keep after passing to NMS in train mode.
        n_test_pre_nms (int): Number of top scored bounding boxes
            to keep before passing to NMS in test mode.
        n_test_post_nms (int): Number of top scored bounding boxes
            to keep after passing to NMS in test mode.
        force_cpu_nms (bool): If this is :obj:`True`,
            always use NMS in CPU mode. If :obj:`False`,
            the NMS mode is selected based on the type of inputs.
        min_size (int): A paramter to determine the threshold on
            discarding bounding boxes based on their sizes.

    """

    def __init__(self,
                 parent_model,
                 nms_thresh=0.7,
                 n_train_pre_nms=12000,
                 n_train_post_nms=2000,
                 n_test_pre_nms=6000,
                 n_test_post_nms=300,
                 min_size=16
                 ):
        self.parent_model = parent_model
        self.nms_thresh = nms_thresh
        self.n_train_pre_nms = n_train_pre_nms
        self.n_train_post_nms = n_train_post_nms
        self.n_test_pre_nms = n_test_pre_nms
        self.n_test_post_nms = n_test_post_nms
        self.min_size = min_size

    def __call__(self, loc, score,
                 anchor, img_size, scale=1.):
        """input should  be ndarray
        Propose RoIs.

        Inputs :obj:`loc, score, anchor` refer to the same anchor when indexed
        by the same index.

        On notations, :math:`R` is the total number of anchors. This is equal
        to product of the height and the width of an image and the number of
        anchor bases per pixel.

        Type of the output is same as the inputs.

        Args:
            loc (array): Predicted offsets and scaling to anchors.
                Its shape is :math:`(R, 4)`.
            score (array): Predicted foreground probability for anchors.
                Its shape is :math:`(R,)`.
            anchor (array): Coordinates of anchors. Its shape is
                :math:`(R, 4)`.
            img_size (tuple of ints): A tuple :obj:`height, width`,
                which contains image size after scaling.
            scale (float): The scaling factor used to scale an image after
                reading it from a file.

        Returns:
            array:
            An array of coordinates of proposal boxes.
            Its shape is :math:`(S, 4)`. :math:`S` is less than
            :obj:`self.n_test_post_nms` in test time and less than
            :obj:`self.n_train_post_nms` in train time. :math:`S` depends on
            the size of the predicted bounding boxes and the number of
            bounding boxes discarded by NMS.

        """
        # NOTE: when test, remember
        # faster_rcnn.eval()
        # to set self.traing = False
        if self.parent_model.training:
            n_pre_nms = self.n_train_pre_nms
            n_post_nms = self.n_train_post_nms
        else:
            n_pre_nms = self.n_test_pre_nms
            n_post_nms = self.n_test_post_nms

        # Convert anchors into proposal via bbox transformations.
        # roi = loc2bbox(anchor, loc)
        roi = loc2bbox(anchor, loc)

        # Clip predicted boxes to image.
        roi[:, slice(0, 4, 2)] = np.clip(
            roi[:, slice(0, 4, 2)], 0, img_size[0])
        roi[:, slice(1, 4, 2)] = np.clip(
            roi[:, slice(1, 4, 2)], 0, img_size[1])

        # Remove predicted boxes with either height or width < threshold.
        min_size = self.min_size * scale
        hs = roi[:, 2] - roi[:, 0]
        ws = roi[:, 3] - roi[:, 1]
        keep = np.where((hs >= min_size) & (ws >= min_size))[0]
        roi = roi[keep, :]
        score = score[keep]

        # Sort all (proposal, score) pairs by score from highest to lowest.
        # Take top pre_nms_topN (e.g. 6000).
        order = score.ravel().argsort()[::-1]
        if n_pre_nms > 0:
            order = order[:n_pre_nms]
        roi = roi[order, :]

        # Apply nms (e.g. threshold = 0.7).
        # Take after_nms_topN (e.g. 300).

        # unNOTE: somthing is wrong here!
        # TODO: remove cuda.to_gpu
        keep = non_maximum_suppression(
            cp.ascontiguousarray(cp.asarray(roi)),
            thresh=self.nms_thresh)
        if n_post_nms > 0:
            keep = keep[:n_post_nms]
        roi = roi[keep]
        return roi