target_layer.py

# Copyright (c) 2020 PaddlePaddle Authors. All Rights Reserved. 
#   
# Licensed under the Apache License, Version 2.0 (the "License");   
# you may not use this file except in compliance with the License.  
# You may obtain a copy of the License at   
#   
#     http://www.apache.org/licenses/LICENSE-2.0    
#   
# Unless required by applicable law or agreed to in writing, software   
# distributed under the License is distributed on an "AS IS" BASIS, 
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  
# See the License for the specific language governing permissions and   
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import paddle

from ppdet.core.workspace import register, serializable

from .target import rpn_anchor_target, generate_proposal_target, generate_mask_target


@register
@serializable
class RPNTargetAssign(object):
    """
    RPN targets assignment module

    The assignment consists of three steps:
        1. Match anchor and ground-truth box, label the anchor with foreground
           or background sample
        2. Sample anchors to keep the properly ratio between foreground and 
           background
        3. Generate the targets for classification and regression branch


    Args:
        batch_size_per_im (int): Total number of RPN samples per image. 
            default 256
        fg_fraction (float): Fraction of anchors that is labeled
            foreground, default 0.5
        positive_overlap (float): Minimum overlap required between an anchor
            and ground-truth box for the (anchor, gt box) pair to be 
            a foreground sample. default 0.7
        negative_overlap (float): Maximum overlap allowed between an anchor
            and ground-truth box for the (anchor, gt box) pair to be 
            a background sample. default 0.3
        use_random (bool): Use random sampling to choose foreground and 
            background boxes, default true.
    """

    def __init__(self,
                 batch_size_per_im=256,
                 fg_fraction=0.5,
                 positive_overlap=0.7,
                 negative_overlap=0.3,
                 use_random=True):
        super(RPNTargetAssign, self).__init__()
        self.batch_size_per_im = batch_size_per_im
        self.fg_fraction = fg_fraction
        self.positive_overlap = positive_overlap
        self.negative_overlap = negative_overlap
        self.use_random = use_random

    def __call__(self, inputs, anchors):
        """
        inputs: ground-truth instances.
        anchor_box (Tensor): [num_anchors, 4], num_anchors are all anchors in all feature maps.
        """
        gt_boxes = inputs['gt_bbox']
        batch_size = len(gt_boxes)
        tgt_labels, tgt_bboxes, tgt_deltas = rpn_anchor_target(
            anchors, gt_boxes, self.batch_size_per_im, self.positive_overlap,
            self.negative_overlap, self.fg_fraction, self.use_random,
            batch_size)
        norm = self.batch_size_per_im * batch_size

        return tgt_labels, tgt_bboxes, tgt_deltas, norm


@register
class BBoxAssigner(object):
    __shared__ = ['num_classes']
    """
    RCNN targets assignment module

    The assignment consists of three steps:
        1. Match RoIs and ground-truth box, label the RoIs with foreground
           or background sample
        2. Sample anchors to keep the properly ratio between foreground and 
           background
        3. Generate the targets for classification and regression branch

    Args:
        batch_size_per_im (int): Total number of RoIs per image. 
            default 512 
        fg_fraction (float): Fraction of RoIs that is labeled
            foreground, default 0.25
        positive_overlap (float): Minimum overlap required between a RoI
            and ground-truth box for the (roi, gt box) pair to be 
            a foreground sample. default 0.5
        negative_overlap (float): Maximum overlap allowed between a RoI 
            and ground-truth box for the (roi, gt box) pair to be 
            a background sample. default 0.5
        use_random (bool): Use random sampling to choose foreground and 
            background boxes, default true
        cascade_iou (list[iou]): The list of overlap to select foreground and 
            background of each stage, which is only used In Cascade RCNN.
        num_classes (int): The number of class.
    """

    def __init__(self,
                 batch_size_per_im=512,
                 fg_fraction=.25,
                 fg_thresh=.5,
                 bg_thresh=.5,
                 use_random=True,
                 cascade_iou=[0.5, 0.6, 0.7],
                 num_classes=80):
        super(BBoxAssigner, self).__init__()
        self.batch_size_per_im = batch_size_per_im
        self.fg_fraction = fg_fraction
        self.fg_thresh = fg_thresh
        self.bg_thresh = bg_thresh
        self.use_random = use_random
        self.cascade_iou = cascade_iou
        self.num_classes = num_classes

    def __call__(self,
                 rpn_rois,
                 rpn_rois_num,
                 inputs,
                 stage=0,
                 is_cascade=False):
        gt_classes = inputs['gt_class']
        gt_boxes = inputs['gt_bbox']
        # rois, tgt_labels, tgt_bboxes, tgt_gt_inds
        # new_rois_num
        outs = generate_proposal_target(
            rpn_rois, gt_classes, gt_boxes, self.batch_size_per_im,
            self.fg_fraction, self.fg_thresh, self.bg_thresh, self.num_classes,
            self.use_random, is_cascade, self.cascade_iou[stage])
        rois = outs[0]
        rois_num = outs[-1]
        # tgt_labels, tgt_bboxes, tgt_gt_inds
        targets = outs[1:4]
        return rois, rois_num, targets


@register
@serializable
class MaskAssigner(object):
    __shared__ = ['num_classes', 'mask_resolution']
    """
    Mask targets assignment module

    The assignment consists of three steps:
        1. Select RoIs labels with foreground.
        2. Encode the RoIs and corresponding gt polygons to generate 
           mask target

    Args:
        num_classes (int): The number of class
        mask_resolution (int): The resolution of mask target, default 14
    """

    def __init__(self, num_classes=80, mask_resolution=14):
        super(MaskAssigner, self).__init__()
        self.num_classes = num_classes
        self.mask_resolution = mask_resolution

    def __call__(self, rois, tgt_labels, tgt_gt_inds, inputs):
        gt_segms = inputs['gt_poly']

        outs = generate_mask_target(gt_segms, rois, tgt_labels, tgt_gt_inds,
                                    self.num_classes, self.mask_resolution)

        # mask_rois, mask_rois_num, tgt_classes, tgt_masks, mask_index, tgt_weights
        return outs