import torch import torch.nn as nn from mmcv.cnn import ConvModule, normal_init from mmcv.ops import DeformConv2d from mmdet.core import multi_apply, multiclass_nms from ..builder import HEADS from .anchor_free_head import AnchorFreeHead INF = 1e8 class FeatureAlign(nn.Module): def __init__(self, in_channels, out_channels, kernel_size=3, deform_groups=4): super(FeatureAlign, self).__init__() offset_channels = kernel_size * kernel_size * 2 self.conv_offset = nn.Conv2d( 4, deform_groups * offset_channels, 1, bias=False) self.conv_adaption = DeformConv2d( in_channels, out_channels, kernel_size=kernel_size, padding=(kernel_size - 1) // 2, deform_groups=deform_groups) self.relu = nn.ReLU(inplace=True) def init_weights(self): normal_init(self.conv_offset, std=0.1) normal_init(self.conv_adaption, std=0.01) def forward(self, x, shape): offset = self.conv_offset(shape) x = self.relu(self.conv_adaption(x, offset)) return x @HEADS.register_module() class FoveaHead(AnchorFreeHead): """FoveaBox: Beyond Anchor-based Object Detector https://arxiv.org/abs/1904.03797 """ def __init__(self, num_classes, in_channels, base_edge_list=(16, 32, 64, 128, 256), scale_ranges=((8, 32), (16, 64), (32, 128), (64, 256), (128, 512)), sigma=0.4, with_deform=False, deform_groups=4, **kwargs): self.base_edge_list = base_edge_list self.scale_ranges = scale_ranges self.sigma = sigma self.with_deform = with_deform self.deform_groups = deform_groups super().__init__(num_classes, in_channels, **kwargs) def _init_layers(self): # box branch super()._init_reg_convs() self.conv_reg = nn.Conv2d(self.feat_channels, 4, 3, padding=1) # cls branch if not self.with_deform: super()._init_cls_convs() self.conv_cls = nn.Conv2d( self.feat_channels, self.cls_out_channels, 3, padding=1) else: self.cls_convs = nn.ModuleList() self.cls_convs.append( ConvModule( self.feat_channels, (self.feat_channels * 4), 3, stride=1, padding=1, conv_cfg=self.conv_cfg, norm_cfg=self.norm_cfg, bias=self.norm_cfg is None)) self.cls_convs.append( ConvModule((self.feat_channels * 4), (self.feat_channels * 4), 1, stride=1, padding=0, conv_cfg=self.conv_cfg, norm_cfg=self.norm_cfg, bias=self.norm_cfg is None)) self.feature_adaption = FeatureAlign( self.feat_channels, self.feat_channels, kernel_size=3, deform_groups=self.deform_groups) self.conv_cls = nn.Conv2d( int(self.feat_channels * 4), self.cls_out_channels, 3, padding=1) def init_weights(self): super().init_weights() if self.with_deform: self.feature_adaption.init_weights() def forward_single(self, x): cls_feat = x reg_feat = x for reg_layer in self.reg_convs: reg_feat = reg_layer(reg_feat) bbox_pred = self.conv_reg(reg_feat) if self.with_deform: cls_feat = self.feature_adaption(cls_feat, bbox_pred.exp()) for cls_layer in self.cls_convs: cls_feat = cls_layer(cls_feat) cls_score = self.conv_cls(cls_feat) return cls_score, bbox_pred def _get_points_single(self, *args, **kwargs): y, x = super()._get_points_single(*args, **kwargs) return y + 0.5, x + 0.5 def loss(self, cls_scores, bbox_preds, gt_bbox_list, gt_label_list, img_metas, gt_bboxes_ignore=None): assert len(cls_scores) == len(bbox_preds) featmap_sizes = [featmap.size()[-2:] for featmap in cls_scores] points = self.get_points(featmap_sizes, bbox_preds[0].dtype, bbox_preds[0].device) num_imgs = cls_scores[0].size(0) flatten_cls_scores = [ cls_score.permute(0, 2, 3, 1).reshape(-1, self.cls_out_channels) for cls_score in cls_scores ] flatten_bbox_preds = [ bbox_pred.permute(0, 2, 3, 1).reshape(-1, 4) for bbox_pred in bbox_preds ] flatten_cls_scores = torch.cat(flatten_cls_scores) flatten_bbox_preds = torch.cat(flatten_bbox_preds) flatten_labels, flatten_bbox_targets = self.get_targets( gt_bbox_list, gt_label_list, featmap_sizes, points) # FG cat_id: [0, num_classes -1], BG cat_id: num_classes pos_inds = ((flatten_labels >= 0) & (flatten_labels < self.num_classes)).nonzero().view(-1) num_pos = len(pos_inds) loss_cls = self.loss_cls( flatten_cls_scores, flatten_labels, avg_factor=num_pos + num_imgs) if num_pos > 0: pos_bbox_preds = flatten_bbox_preds[pos_inds] pos_bbox_targets = flatten_bbox_targets[pos_inds] pos_weights = pos_bbox_targets.new_zeros( pos_bbox_targets.size()) + 1.0 loss_bbox = self.loss_bbox( pos_bbox_preds, pos_bbox_targets, pos_weights, avg_factor=num_pos) else: loss_bbox = torch.tensor( 0, dtype=flatten_bbox_preds.dtype, device=flatten_bbox_preds.device) return dict(loss_cls=loss_cls, loss_bbox=loss_bbox) def get_targets(self, gt_bbox_list, gt_label_list, featmap_sizes, points): label_list, bbox_target_list = multi_apply( self._get_target_single, gt_bbox_list, gt_label_list, featmap_size_list=featmap_sizes, point_list=points) flatten_labels = [ torch.cat([ labels_level_img.flatten() for labels_level_img in labels_level ]) for labels_level in zip(*label_list) ] flatten_bbox_targets = [ torch.cat([ bbox_targets_level_img.reshape(-1, 4) for bbox_targets_level_img in bbox_targets_level ]) for bbox_targets_level in zip(*bbox_target_list) ] flatten_labels = torch.cat(flatten_labels) flatten_bbox_targets = torch.cat(flatten_bbox_targets) return flatten_labels, flatten_bbox_targets def _get_target_single(self, gt_bboxes_raw, gt_labels_raw, featmap_size_list=None, point_list=None): gt_areas = torch.sqrt((gt_bboxes_raw[:, 2] - gt_bboxes_raw[:, 0]) * (gt_bboxes_raw[:, 3] - gt_bboxes_raw[:, 1])) label_list = [] bbox_target_list = [] # for each pyramid, find the cls and box target for base_len, (lower_bound, upper_bound), stride, featmap_size, \ (y, x) in zip(self.base_edge_list, self.scale_ranges, self.strides, featmap_size_list, point_list): # FG cat_id: [0, num_classes -1], BG cat_id: num_classes labels = gt_labels_raw.new_zeros(featmap_size) + self.num_classes bbox_targets = gt_bboxes_raw.new(featmap_size[0], featmap_size[1], 4) + 1 # scale assignment hit_indices = ((gt_areas >= lower_bound) & (gt_areas <= upper_bound)).nonzero().flatten() if len(hit_indices) == 0: label_list.append(labels) bbox_target_list.append(torch.log(bbox_targets)) continue _, hit_index_order = torch.sort(-gt_areas[hit_indices]) hit_indices = hit_indices[hit_index_order] gt_bboxes = gt_bboxes_raw[hit_indices, :] / stride gt_labels = gt_labels_raw[hit_indices] half_w = 0.5 * (gt_bboxes[:, 2] - gt_bboxes[:, 0]) half_h = 0.5 * (gt_bboxes[:, 3] - gt_bboxes[:, 1]) # valid fovea area: left, right, top, down pos_left = torch.ceil( gt_bboxes[:, 0] + (1 - self.sigma) * half_w - 0.5).long().\ clamp(0, featmap_size[1] - 1) pos_right = torch.floor( gt_bboxes[:, 0] + (1 + self.sigma) * half_w - 0.5).long().\ clamp(0, featmap_size[1] - 1) pos_top = torch.ceil( gt_bboxes[:, 1] + (1 - self.sigma) * half_h - 0.5).long().\ clamp(0, featmap_size[0] - 1) pos_down = torch.floor( gt_bboxes[:, 1] + (1 + self.sigma) * half_h - 0.5).long().\ clamp(0, featmap_size[0] - 1) for px1, py1, px2, py2, label, (gt_x1, gt_y1, gt_x2, gt_y2) in \ zip(pos_left, pos_top, pos_right, pos_down, gt_labels, gt_bboxes_raw[hit_indices, :]): labels[py1:py2 + 1, px1:px2 + 1] = label bbox_targets[py1:py2 + 1, px1:px2 + 1, 0] = \ (stride * x[py1:py2 + 1, px1:px2 + 1] - gt_x1) / base_len bbox_targets[py1:py2 + 1, px1:px2 + 1, 1] = \ (stride * y[py1:py2 + 1, px1:px2 + 1] - gt_y1) / base_len bbox_targets[py1:py2 + 1, px1:px2 + 1, 2] = \ (gt_x2 - stride * x[py1:py2 + 1, px1:px2 + 1]) / base_len bbox_targets[py1:py2 + 1, px1:px2 + 1, 3] = \ (gt_y2 - stride * y[py1:py2 + 1, px1:px2 + 1]) / base_len bbox_targets = bbox_targets.clamp(min=1. / 16, max=16.) label_list.append(labels) bbox_target_list.append(torch.log(bbox_targets)) return label_list, bbox_target_list def get_bboxes(self, cls_scores, bbox_preds, img_metas, cfg=None, rescale=None): assert len(cls_scores) == len(bbox_preds) num_levels = len(cls_scores) featmap_sizes = [featmap.size()[-2:] for featmap in cls_scores] points = self.get_points( featmap_sizes, bbox_preds[0].dtype, bbox_preds[0].device, flatten=True) result_list = [] for img_id in range(len(img_metas)): cls_score_list = [ cls_scores[i][img_id].detach() for i in range(num_levels) ] bbox_pred_list = [ bbox_preds[i][img_id].detach() for i in range(num_levels) ] img_shape = img_metas[img_id]['img_shape'] scale_factor = img_metas[img_id]['scale_factor'] det_bboxes = self._get_bboxes_single(cls_score_list, bbox_pred_list, featmap_sizes, points, img_shape, scale_factor, cfg, rescale) result_list.append(det_bboxes) return result_list def _get_bboxes_single(self, cls_scores, bbox_preds, featmap_sizes, point_list, img_shape, scale_factor, cfg, rescale=False): cfg = self.test_cfg if cfg is None else cfg assert len(cls_scores) == len(bbox_preds) == len(point_list) det_bboxes = [] det_scores = [] for cls_score, bbox_pred, featmap_size, stride, base_len, (y, x) \ in zip(cls_scores, bbox_preds, featmap_sizes, self.strides, self.base_edge_list, point_list): assert cls_score.size()[-2:] == bbox_pred.size()[-2:] scores = cls_score.permute(1, 2, 0).reshape( -1, self.cls_out_channels).sigmoid() bbox_pred = bbox_pred.permute(1, 2, 0).reshape(-1, 4).exp() nms_pre = cfg.get('nms_pre', -1) if (nms_pre > 0) and (scores.shape[0] > nms_pre): max_scores, _ = scores.max(dim=1) _, topk_inds = max_scores.topk(nms_pre) bbox_pred = bbox_pred[topk_inds, :] scores = scores[topk_inds, :] y = y[topk_inds] x = x[topk_inds] x1 = (stride * x - base_len * bbox_pred[:, 0]).\ clamp(min=0, max=img_shape[1] - 1) y1 = (stride * y - base_len * bbox_pred[:, 1]).\ clamp(min=0, max=img_shape[0] - 1) x2 = (stride * x + base_len * bbox_pred[:, 2]).\ clamp(min=0, max=img_shape[1] - 1) y2 = (stride * y + base_len * bbox_pred[:, 3]).\ clamp(min=0, max=img_shape[0] - 1) bboxes = torch.stack([x1, y1, x2, y2], -1) det_bboxes.append(bboxes) det_scores.append(scores) det_bboxes = torch.cat(det_bboxes) if rescale: det_bboxes /= det_bboxes.new_tensor(scale_factor) det_scores = torch.cat(det_scores) padding = det_scores.new_zeros(det_scores.shape[0], 1) # remind that we set FG labels to [0, num_class-1] since mmdet v2.0 # BG cat_id: num_class det_scores = torch.cat([det_scores, padding], dim=1) det_bboxes, det_labels = multiclass_nms(det_bboxes, det_scores, cfg.score_thr, cfg.nms, cfg.max_per_img) return det_bboxes, det_labels