Пример #1
0
    def __getitem__(self, idx):
        img, anno = super(COCODataset, self).__getitem__(idx)

        # filter crowd annotations
        # TODO might be better to add an extra field
        anno = [obj for obj in anno if obj["iscrowd"] == 0]

        boxes = [obj["bbox"] for obj in anno]
        boxes = torch.as_tensor(boxes).reshape(-1, 4)  # guard against no boxes
        target = BoxList(boxes, img.size, mode="xywh").convert("xyxy")

        classes = [obj["category_id"] for obj in anno]
        classes = [self.json_category_id_to_contiguous_id[c] for c in classes]
        classes = torch.tensor(classes)
        target.add_field("labels", classes)

        masks = [obj["segmentation"] for obj in anno]
        masks = SegmentationMask(masks, img.size)
        target.add_field("masks", masks)

        if anno and "keypoints" in anno[0]:
            keypoints = [obj["keypoints"] for obj in anno]
            keypoints = PersonKeypoints(keypoints, img.size)
            target.add_field("keypoints", keypoints)

        target = target.clip_to_image(remove_empty=True)

        if self.transforms is not None:
            img, target = self.transforms(img, target)

        return img, target, idx
Пример #2
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    def forward_for_single_feature_map(self, anchors, objectness,
                                       box_regression):
        """
        Arguments:
            anchors: list[BoxList]
            objectness: tensor of size N, A, H, W
            box_regression: tensor of size N, A * 4, H, W
        """
        device = objectness.device
        N, A, H, W = objectness.shape

        # put in the same format as anchors
        objectness = permute_and_flatten(objectness, N, A, 1, H, W).view(N, -1)
        objectness = objectness.sigmoid()

        box_regression = permute_and_flatten(box_regression, N, A, 4, H, W)

        num_anchors = A * H * W

        pre_nms_top_n = min(self.pre_nms_top_n, num_anchors)
        objectness, topk_idx = objectness.topk(pre_nms_top_n,
                                               dim=1,
                                               sorted=True)

        batch_idx = torch.arange(N, device=device)[:, None]
        box_regression = box_regression[batch_idx, topk_idx]

        image_shapes = [box.size for box in anchors]
        concat_anchors = torch.cat([a.bbox for a in anchors], dim=0)
        concat_anchors = concat_anchors.reshape(N, -1, 4)[batch_idx, topk_idx]

        proposals = self.box_coder.decode(box_regression.view(-1, 4),
                                          concat_anchors.view(-1, 4))

        proposals = proposals.view(N, -1, 4)

        result = []
        for proposal, score, im_shape in zip(proposals, objectness,
                                             image_shapes):
            boxlist = BoxList(proposal, im_shape, mode="xyxy")
            boxlist.add_field("objectness", score)
            boxlist = boxlist.clip_to_image(remove_empty=False)
            boxlist = remove_small_boxes(boxlist, self.min_size)
            boxlist = boxlist_nms(
                boxlist,
                self.nms_thresh,
                max_proposals=self.post_nms_top_n,
                score_field="objectness",
            )
            result.append(boxlist)
        return result
def _test_feature_extractors(self, extractors, overwrite_cfgs,
                             overwrite_in_channels):
    ''' Make sure roi box feature extractors run '''

    self.assertGreater(len(extractors), 0)

    in_channels_default = 64

    for name, builder in extractors.items():
        print('Testing {}...'.format(name))
        if name in overwrite_cfgs:
            cfg = load_config(overwrite_cfgs[name])
        else:
            # Use default config if config file is not specified
            cfg = copy.deepcopy(g_cfg)

        in_channels = overwrite_in_channels.get(name, in_channels_default)

        fe = builder(cfg, in_channels)
        self.assertIsNotNone(
            getattr(fe, 'out_channels', None),
            'Need to provide out_channels for feature extractor {}'.format(
                name))

        N, C_in, H, W = 2, in_channels, 24, 32
        input = torch.rand([N, C_in, H, W], dtype=torch.float32)
        bboxes = [[1, 1, 10, 10], [5, 5, 8, 8], [2, 2, 3, 4]]
        img_size = [384, 512]
        box_list = BoxList(bboxes, img_size, "xyxy")
        out = fe([input], [box_list] * N)
        self.assertEqual(out.shape[:2],
                         torch.Size([N * len(bboxes), fe.out_channels]))
Пример #4
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 def prepare_boxlist(self, boxes, scores, image_shape):
     """
     Returns BoxList from `boxes` and adds probability scores information
     as an extra field
     `boxes` has shape (#detections, 4 * #classes), where each row represents
     a list of predicted bounding boxes for each of the object classes in the
     dataset (including the background class). The detections in each row
     originate from the same object proposal.
     `scores` has shape (#detection, #classes), where each row represents a list
     of object detection confidence scores for each of the object classes in the
     dataset (including the background class). `scores[i, j]`` corresponds to the
     box at `boxes[i, j * 4:(j + 1) * 4]`.
     """
     boxes = boxes.reshape(-1, 4)
     scores = scores.reshape(-1)
     boxlist = BoxList(boxes, image_shape, mode="xyxy")
     boxlist.add_field("scores", scores)
     return boxlist
Пример #5
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    def __getitem__(self, item):
        img = Image.open(self.image_lists[item]).convert("RGB")

        # dummy target
        w, h = img.size
        target = BoxList([[0, 0, w, h]], img.size, mode="xyxy")

        if self.transforms is not None:
            img, target = self.transforms(img, target)

        return img, target
Пример #6
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    def forward(self, x, boxes):
        """
        Arguments:
            x (Tensor): the mask logits
            boxes (list[BoxList]): bounding boxes that are used as
                reference, one for ech image

        Returns:
            results (list[BoxList]): one BoxList for each image, containing
                the extra field mask
        """
        mask_prob = x.sigmoid()

        # select masks coresponding to the predicted classes
        num_masks = x.shape[0]
        labels = [bbox.get_field("labels") for bbox in boxes]
        labels = torch.cat(labels)
        index = torch.arange(num_masks, device=labels.device)
        mask_prob = mask_prob[index, labels][:, None]

        boxes_per_image = [len(box) for box in boxes]
        mask_prob = mask_prob.split(boxes_per_image, dim=0)

        if self.masker:
            mask_prob = self.masker(mask_prob, boxes)

        results = []
        for prob, box in zip(mask_prob, boxes):
            bbox = BoxList(box.bbox, box.size, mode="xyxy")
            for field in box.fields():
                bbox.add_field(field, box.get_field(field))
            bbox.add_field("mask", prob)
            results.append(bbox)

        return results
Пример #7
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 def forward(self, image_list, feature_maps):
     grid_sizes = [feature_map.shape[-2:] for feature_map in feature_maps]
     anchors_over_all_feature_maps = self.grid_anchors(grid_sizes)
     anchors = []
     for i, (image_height, image_width) in enumerate(image_list.image_sizes):
         anchors_in_image = []
         for anchors_per_feature_map in anchors_over_all_feature_maps:
             boxlist = BoxList(
                 anchors_per_feature_map, (image_width, image_height), mode="xyxy"
             )
             self.add_visibility_to(boxlist)
             anchors_in_image.append(boxlist)
         anchors.append(anchors_in_image)
     return anchors
Пример #8
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    def __getitem__(self, idx):
        filename = self.img_key_list[idx]

        img = cv2.imread(self.img_dict[filename], cv2.IMREAD_COLOR)
        img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

        # img = Image.open(self.img_dict[filename]).convert("RGB")
        height, width = img.shape[:2]

        # target settings
        boxes = []
        temp_masks = []
        masks = []
        gt_classes = []

        for ann_info in self.ann_info[filename]:
            mask = np.zeros((height, width))

            bndbox = ann_info[:4]
            mask[bndbox[1]:bndbox[3], bndbox[0]:bndbox[2]] = 1

            x1, y1, x2, y2 = ann_info[:4]
            temp_mask = [[x1, y1, x1, y2, x2, y2, x2, y1]]
            temp_masks.append(temp_mask)

            boxes.append(bndbox)
            masks.append([mask])

            # 만약 클래스가 번호가 아닌 이름으로 있다면 아래 코드를 사용한다.
            # gt_classes.append(self.class_to_ind[ann_info[-1]])
            gt_classes.append(ann_info[-1])

        img, boxes, temp_masks = img_and_key_point_augmentation(
            self.augmentation, img, boxes, temp_masks)
        img = Image.fromarray(img, mode="RGB")

        target = BoxList(torch.tensor(boxes, dtype=torch.float32),
                         (width, height),
                         mode="xyxy")
        target.add_field("labels", torch.tensor(gt_classes))

        seg_masks = SegmentationMask(temp_masks, (width, height),
                                     type=self.mask_type)
        target.add_field("masks", seg_masks)

        target = target.clip_to_image(remove_empty=True)

        if self.transforms is not None:
            img, target = self.transforms(img, target)

        return img, target, idx
Пример #9
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    def get_groundtruth(self, index):
        img_id = self.ids[index]
        anno = ET.parse(self._annopath % img_id).getroot()
        anno = self._preprocess_annotation(anno)

        height, width = anno["im_info"]
        target = BoxList(anno["boxes"], (width, height), mode="xyxy")
        target.add_field("labels", anno["labels"])
        target.add_field("difficult", anno["difficult"])
        return target
Пример #10
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    def get_groundtruth(self, filename, width, height, aug_det):
        anno = self._preprocess_annotation(self.ann_info[filename], aug_det)

        target = BoxList(anno["boxes"], (width, height), mode="xyxy")  # .convert("xyxy")
        target.add_field("labels", anno["labels"])

        masks = SegmentationMask(anno["masks"], (width, height), type=self.mask_type)
        target.add_field("masks", masks)

        return target
    def get_groundtruth(self, filename):

        # filename = '1.2.840.113619.2.256.896737935203.1468394276.4947'
        img = cv2.imread(self.img_dict[filename], cv2.IMREAD_COLOR)
        # img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
        img, ratio, pad = self.img_resize_keep_aspect_ratio_with_padding(img)
        height, width = img.shape[:2]

        boxes = []
        masks = []
        gt_classes = []

        for ann_info in self.ann_info[filename]:
            cls_num, mask_file = ann_info
            mask = cv2.imread(mask_file, cv2.IMREAD_GRAYSCALE)

            # 하나의 클래스의 여러 분절된 세그먼테이션을 모두 포함하는 바운딩 박스를 구함
            bbox_points, mask_points = self.find_bounding_square(mask)
            bbox_points, mask_points = self.apply_bb_pts_ratio_pad(
                bbox_points, mask_points, ratio, pad)
            mask_points = self.simple_pts(mask_points)

            x1, y1, x2, y2 = self.getBiggestBoundbox(bbox_points)
            bbox = [x1, y1, x2, y2]

            # # # for debug
            # debug_show_img_pts(self.img_resize_keep_aspect_ratio_with_padding(mask)[0], mask_points)
            # debug_show_img_pts(self.img_resize_keep_aspect_ratio_with_padding(mask)[0], [bbox])
            # exit()

            boxes.append(bbox)
            masks.append(mask_points)
            gt_classes.append(cls_num)

        img, boxes, masks = img_and_key_point_augmentation(
            self.augmentation, img, boxes, masks)

        anno = {
            "boxes": torch.tensor(boxes, dtype=torch.float32),
            "masks": masks,
            "labels": torch.tensor(gt_classes),
        }

        target = BoxList(anno["boxes"], (width, height), mode="xyxy")
        target.add_field("labels", anno["labels"])

        masks = SegmentationMask(anno["masks"], (width, height),
                                 type=self.mask_type)
        target.add_field("masks", masks)

        return img, target
Пример #12
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    def select_over_all_levels(self, boxlists):
        num_images = len(boxlists)
        results = []
        for i in range(num_images):
            scores = boxlists[i].get_field("scores")
            labels = boxlists[i].get_field("labels")
            boxes = boxlists[i].bbox
            boxlist = boxlists[i]
            result = []
            # skip the background
            for j in range(1, self.num_classes):
                inds = (labels == j).nonzero().view(-1)

                scores_j = scores[inds]
                boxes_j = boxes[inds, :].view(-1, 4)
                boxlist_for_class = BoxList(boxes_j, boxlist.size, mode="xyxy")
                boxlist_for_class.add_field("scores", scores_j)
                boxlist_for_class = boxlist_nms(boxlist_for_class,
                                                self.nms_thresh,
                                                score_field="scores")
                num_labels = len(boxlist_for_class)
                boxlist_for_class.add_field(
                    "labels",
                    torch.full((num_labels, ),
                               j,
                               dtype=torch.int64,
                               device=scores.device))
                result.append(boxlist_for_class)

            result = cat_boxlist(result)
            number_of_detections = len(result)

            # Limit to max_per_image detections **over all classes**
            if number_of_detections > self.fpn_post_nms_top_n > 0:
                cls_scores = result.get_field("scores")
                image_thresh, _ = torch.kthvalue(
                    cls_scores.cpu(),
                    number_of_detections - self.fpn_post_nms_top_n + 1)
                keep = cls_scores >= image_thresh.item()
                keep = torch.nonzero(keep).squeeze(1)
                result = result[keep]
            results.append(result)
        return results
Пример #13
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    def filter_results(self, boxlist, num_classes):
        """Returns bounding-box detection results by thresholding on scores and
        applying non-maximum suppression (NMS).
        """
        # unwrap the boxlist to avoid additional overhead.
        # if we had multi-class NMS, we could perform this directly on the boxlist
        boxes = boxlist.bbox.reshape(-1, num_classes * 4)
        scores = boxlist.get_field("scores").reshape(-1, num_classes)

        device = scores.device
        result = []
        # Apply threshold on detection probabilities and apply NMS
        # Skip j = 0, because it's the background class
        inds_all = scores > self.score_thresh
        for j in range(1, num_classes):
            inds = inds_all[:, j].nonzero().squeeze(1)
            scores_j = scores[inds, j]
            boxes_j = boxes[inds, j * 4 : (j + 1) * 4]
            boxlist_for_class = BoxList(boxes_j, boxlist.size, mode="xyxy")
            boxlist_for_class.add_field("scores", scores_j)
            boxlist_for_class = boxlist_nms(
                boxlist_for_class, self.nms
            )
            num_labels = len(boxlist_for_class)
            boxlist_for_class.add_field(
                "labels", torch.full((num_labels,), j, dtype=torch.int64, device=device)
            )
            result.append(boxlist_for_class)

        result = cat_boxlist(result)
        number_of_detections = len(result)

        # Limit to max_per_image detections **over all classes**
        if number_of_detections > self.detections_per_img > 0:
            cls_scores = result.get_field("scores")
            image_thresh, _ = torch.kthvalue(
                cls_scores.cpu(), number_of_detections - self.detections_per_img + 1
            )
            keep = cls_scores >= image_thresh.item()
            keep = torch.nonzero(keep).squeeze(1)
            result = result[keep]
        return result
Пример #14
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    def get_groundtruth(self, filename):
        img = cv2.imread(self.img_dict[filename], cv2.IMREAD_COLOR)
        # img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
        img = self.resize_keep_aspect_ratio_with_padding(img)
        height, width = img.shape[:2]

        boxes = []
        masks = []
        gt_classes = []

        for ann_info in self.ann_info[filename]:
            cls_num, mask_file = ann_info
            mask = cv2.imread(mask_file, cv2.IMREAD_GRAYSCALE)
            mask = self.resize_keep_aspect_ratio_with_padding(mask)

            # 하나의 클래스의 여러 분절된 세그먼테이션을 모두 포함하는 바운딩 박스를 구함
            bbox_points, mask_points = self.find_bounding_square(mask)

            x1, y1, x2, y2 = self.getBiggestBoundbox(bbox_points)
            bbox = [x1, y1, x2, y2]
            # print('w:{} h:{} len:{} pts:{} x1<x2:{} y1<y2:{} name:{}'.format(x2-x1, y2-y1, len(bbox_points), bbox_points, x1<x2, y1<y2, filename))

            boxes.append(bbox)
            masks.append(mask_points)
            gt_classes.append(cls_num)

        img, boxes, masks = img_and_key_point_augmentation(self.augmentation, img, boxes, masks)

        anno = {
            "boxes": torch.tensor(boxes, dtype=torch.float32),
            "masks": masks,
            "labels": torch.tensor(gt_classes),
        }

        target = BoxList(anno["boxes"], (width, height), mode="xyxy")
        target.add_field("labels", anno["labels"])

        masks = SegmentationMask(anno["masks"], (width, height), type=self.mask_type)
        target.add_field("masks", masks)

        return img, target
Пример #15
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    def forward(self, x, boxes):
        mask_prob = x

        scores = None
        if self.keypointer:
            mask_prob, scores = self.keypointer(x, boxes)

        assert len(boxes) == 1, "Only non-batched inference supported for now"
        boxes_per_image = [box.bbox.size(0) for box in boxes]
        mask_prob = mask_prob.split(boxes_per_image, dim=0)
        scores = scores.split(boxes_per_image, dim=0)

        results = []
        for prob, box, score in zip(mask_prob, boxes, scores):
            bbox = BoxList(box.bbox, box.size, mode="xyxy")
            for field in box.fields():
                bbox.add_field(field, box.get_field(field))
            prob = PersonKeypoints(prob, box.size)
            prob.add_field("logits", score)
            bbox.add_field("keypoints", prob)
            results.append(bbox)

        return results
Пример #16
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    def forward_for_single_feature_map(self, anchors, box_cls, box_regression):
        """
        Arguments:
            anchors: list[BoxList]
            box_cls: tensor of size N, A * C, H, W
            box_regression: tensor of size N, A * 4, H, W
        """
        device = box_cls.device
        N, _, H, W = box_cls.shape
        A = box_regression.size(1) // 4
        C = box_cls.size(1) // A

        # put in the same format as anchors
        box_cls = permute_and_flatten(box_cls, N, A, C, H, W)
        box_cls = box_cls.sigmoid()

        box_regression = permute_and_flatten(box_regression, N, A, 4, H, W)
        box_regression = box_regression.reshape(N, -1, 4)

        num_anchors = A * H * W

        candidate_inds = box_cls > self.pre_nms_thresh

        pre_nms_top_n = candidate_inds.view(N, -1).sum(1)
        pre_nms_top_n = pre_nms_top_n.clamp(max=self.pre_nms_top_n)

        results = []
        for per_box_cls, per_box_regression, per_pre_nms_top_n, \
        per_candidate_inds, per_anchors in zip(
            box_cls,
            box_regression,
            pre_nms_top_n,
            candidate_inds,
            anchors):

            # Sort and select TopN
            # TODO most of this can be made out of the loop for
            # all images.
            # TODO:Yang: Not easy to do. Because the numbers of detections are
            # different in each image. Therefore, this part needs to be done
            # per image.
            per_box_cls = per_box_cls[per_candidate_inds]

            per_box_cls, top_k_indices = \
                    per_box_cls.topk(per_pre_nms_top_n, sorted=False)

            per_candidate_nonzeros = \
                    per_candidate_inds.nonzero()[top_k_indices, :]

            per_box_loc = per_candidate_nonzeros[:, 0]
            per_class = per_candidate_nonzeros[:, 1]
            per_class += 1

            detections = self.box_coder.decode(
                per_box_regression[per_box_loc, :].view(-1, 4),
                per_anchors.bbox[per_box_loc, :].view(-1, 4))

            boxlist = BoxList(detections, per_anchors.size, mode="xyxy")
            boxlist.add_field("labels", per_class)
            boxlist.add_field("scores", per_box_cls)
            boxlist = boxlist.clip_to_image(remove_empty=False)
            boxlist = remove_small_boxes(boxlist, self.min_size)
            results.append(boxlist)

        return results
Пример #17
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def calc_detection_voc_prec_rec(gt_boxlists, pred_boxlists, iou_thresh=0.5):
    """Calculate precision and recall based on evaluation code of PASCAL VOC.
    This function calculates precision and recall of
    predicted bounding boxes obtained from a dataset which has :math:`N`
    images.
    The code is based on the evaluation code used in PASCAL VOC Challenge.
   """
    n_pos = defaultdict(int)
    score = defaultdict(list)
    match = defaultdict(list)
    for gt_boxlist, pred_boxlist in zip(gt_boxlists, pred_boxlists):
        pred_bbox = pred_boxlist.bbox.numpy()
        pred_label = pred_boxlist.get_field("labels").numpy()
        pred_score = pred_boxlist.get_field("scores").numpy()
        gt_bbox = gt_boxlist.bbox.numpy()
        gt_label = gt_boxlist.get_field("labels").numpy()
        gt_difficult = gt_boxlist.get_field("difficult").numpy()

        for l in np.unique(np.concatenate((pred_label, gt_label)).astype(int)):
            pred_mask_l = pred_label == l
            pred_bbox_l = pred_bbox[pred_mask_l]
            pred_score_l = pred_score[pred_mask_l]
            # sort by score
            order = pred_score_l.argsort()[::-1]
            pred_bbox_l = pred_bbox_l[order]
            pred_score_l = pred_score_l[order]

            gt_mask_l = gt_label == l
            gt_bbox_l = gt_bbox[gt_mask_l]
            gt_difficult_l = gt_difficult[gt_mask_l]

            n_pos[l] += np.logical_not(gt_difficult_l).sum()
            score[l].extend(pred_score_l)

            if len(pred_bbox_l) == 0:
                continue
            if len(gt_bbox_l) == 0:
                match[l].extend((0, ) * pred_bbox_l.shape[0])
                continue

            # VOC evaluation follows integer typed bounding boxes.
            pred_bbox_l = pred_bbox_l.copy()
            pred_bbox_l[:, 2:] += 1
            gt_bbox_l = gt_bbox_l.copy()
            gt_bbox_l[:, 2:] += 1
            iou = boxlist_iou(
                BoxList(pred_bbox_l, gt_boxlist.size),
                BoxList(gt_bbox_l, gt_boxlist.size),
            ).numpy()
            gt_index = iou.argmax(axis=1)
            # set -1 if there is no matching ground truth
            gt_index[iou.max(axis=1) < iou_thresh] = -1
            del iou

            selec = np.zeros(gt_bbox_l.shape[0], dtype=bool)
            for gt_idx in gt_index:
                if gt_idx >= 0:
                    if gt_difficult_l[gt_idx]:
                        match[l].append(-1)
                    else:
                        if not selec[gt_idx]:
                            match[l].append(1)
                        else:
                            match[l].append(0)
                    selec[gt_idx] = True
                else:
                    match[l].append(0)

    n_fg_class = max(n_pos.keys()) + 1
    prec = [None] * n_fg_class
    rec = [None] * n_fg_class

    for l in n_pos.keys():
        score_l = np.array(score[l])
        match_l = np.array(match[l], dtype=np.int8)

        order = score_l.argsort()[::-1]
        match_l = match_l[order]

        tp = np.cumsum(match_l == 1)
        fp = np.cumsum(match_l == 0)

        # If an element of fp + tp is 0,
        # the corresponding element of prec[l] is nan.
        prec[l] = tp / (fp + tp)
        # If n_pos[l] is 0, rec[l] is None.
        if n_pos[l] > 0:
            rec[l] = tp / n_pos[l]

    return prec, rec
Пример #18
0
def evaluate_box_proposals(predictions,
                           dataset,
                           thresholds=None,
                           area="all",
                           limit=None):
    """Evaluate detection proposal recall metrics. This function is a much
    faster alternative to the official COCO API recall evaluation code. However,
    it produces slightly different results.
    """
    # Record max overlap value for each gt box
    # Return vector of overlap values
    areas = {
        "all": 0,
        "small": 1,
        "medium": 2,
        "large": 3,
        "96-128": 4,
        "128-256": 5,
        "256-512": 6,
        "512-inf": 7,
    }
    area_ranges = [
        [0**2, 1e5**2],  # all
        [0**2, 32**2],  # small
        [32**2, 96**2],  # medium
        [96**2, 1e5**2],  # large
        [96**2, 128**2],  # 96-128
        [128**2, 256**2],  # 128-256
        [256**2, 512**2],  # 256-512
        [512**2, 1e5**2],
    ]  # 512-inf
    assert area in areas, "Unknown area range: {}".format(area)
    area_range = area_ranges[areas[area]]
    gt_overlaps = []
    num_pos = 0

    for image_id, prediction in enumerate(predictions):
        original_id = dataset.id_to_img_map[image_id]

        img_info = dataset.get_img_info(image_id)
        image_width = img_info["width"]
        image_height = img_info["height"]
        prediction = prediction.resize((image_width, image_height))

        # sort predictions in descending order
        # TODO maybe remove this and make it explicit in the documentation
        inds = prediction.get_field("objectness").sort(descending=True)[1]
        prediction = prediction[inds]

        ann_ids = dataset.coco.getAnnIds(imgIds=original_id)
        anno = dataset.coco.loadAnns(ann_ids)
        gt_boxes = [obj["bbox"] for obj in anno if obj["iscrowd"] == 0]
        gt_boxes = torch.as_tensor(gt_boxes).reshape(
            -1, 4)  # guard against no boxes
        gt_boxes = BoxList(gt_boxes, (image_width, image_height),
                           mode="xywh").convert("xyxy")
        gt_areas = torch.as_tensor(
            [obj["area"] for obj in anno if obj["iscrowd"] == 0])

        if len(gt_boxes) == 0:
            continue

        valid_gt_inds = (gt_areas >= area_range[0]) & (gt_areas <=
                                                       area_range[1])
        gt_boxes = gt_boxes[valid_gt_inds]

        num_pos += len(gt_boxes)

        if len(gt_boxes) == 0:
            continue

        if len(prediction) == 0:
            continue

        if limit is not None and len(prediction) > limit:
            prediction = prediction[:limit]

        overlaps = boxlist_iou(prediction, gt_boxes)

        _gt_overlaps = torch.zeros(len(gt_boxes))
        for j in range(min(len(prediction), len(gt_boxes))):
            # find which proposal box maximally covers each gt box
            # and get the iou amount of coverage for each gt box
            max_overlaps, argmax_overlaps = overlaps.max(dim=0)

            # find which gt box is 'best' covered (i.e. 'best' = most iou)
            gt_ovr, gt_ind = max_overlaps.max(dim=0)
            assert gt_ovr >= 0
            # find the proposal box that covers the best covered gt box
            box_ind = argmax_overlaps[gt_ind]
            # record the iou coverage of this gt box
            _gt_overlaps[j] = overlaps[box_ind, gt_ind]
            assert _gt_overlaps[j] == gt_ovr
            # mark the proposal box and the gt box as used
            overlaps[box_ind, :] = -1
            overlaps[:, gt_ind] = -1

        # append recorded iou coverage level
        gt_overlaps.append(_gt_overlaps)
    gt_overlaps = torch.cat(gt_overlaps, dim=0)
    gt_overlaps, _ = torch.sort(gt_overlaps)

    if thresholds is None:
        step = 0.05
        thresholds = torch.arange(0.5, 0.95 + 1e-5, step, dtype=torch.float32)
    recalls = torch.zeros_like(thresholds)
    # compute recall for each iou threshold
    for i, t in enumerate(thresholds):
        recalls[i] = (gt_overlaps >= t).float().sum() / float(num_pos)
    # ar = 2 * np.trapz(recalls, thresholds)
    ar = recalls.mean()
    return {
        "ar": ar,
        "recalls": recalls,
        "thresholds": thresholds,
        "gt_overlaps": gt_overlaps,
        "num_pos": num_pos,
    }