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| import numpy as np | |
| class FasterRcnnBoxCoder: | |
| """Faster RCNN box coder. | |
| Notes: | |
| boxes should be in cxcywh format. | |
| """ | |
| def __init__(self, stddevs=None): | |
| """Constructor for FasterRcnnBoxCoder. | |
| Args: | |
| stddevs: List of 4 positive scalars to scale ty, tx, th and tw. | |
| If set to None, does not perform scaling. For Faster RCNN, | |
| the open-source implementation recommends using [0.1, 0.1, 0.2, 0.2]. | |
| """ | |
| if stddevs: | |
| assert len(stddevs) == 4 | |
| for scalar in stddevs: | |
| assert scalar > 0 | |
| self.stddevs = stddevs | |
| def encode(self, boxes, reference_boxes, copy=True): | |
| """Encode boxes with respect to reference boxes. | |
| """ | |
| if copy: | |
| boxes = boxes.copy() | |
| boxes[..., 2:4] += 1e-8 | |
| reference_boxes[..., 2:4] += 1e-8 | |
| boxes[..., 0:2] -= reference_boxes[..., 0:2] | |
| boxes[..., 0:2] /= reference_boxes[..., 2:4] | |
| boxes[..., 2:4] /= reference_boxes[..., 2:4] | |
| boxes[..., 2:4] = np.log(boxes[..., 2:4], boxes[..., 2:4]) | |
| if self.stddevs: | |
| boxes[..., 0:4] /= self.stddevs | |
| return boxes | |
| def decode(self, rel_boxes, reference_boxes, copy=True): | |
| """Decode relative codes to boxes. | |
| """ | |
| if copy: | |
| rel_boxes = rel_boxes.copy() | |
| if self.stddevs: | |
| rel_boxes[..., 0:4] *= self.stddevs | |
| rel_boxes[..., 0:2] *= reference_boxes[..., 2:4] | |
| rel_boxes[..., 0:2] += reference_boxes[..., 0:2] | |
| rel_boxes[..., 2:4] = np.exp(rel_boxes[..., 2:4], rel_boxes[..., 2:4]) | |
| rel_boxes[..., 2:4] *= reference_boxes[..., 2:4] | |
| return rel_boxes | |
| def decode_points(self, rel_points, reference_boxes, copy=True): | |
| """Decode relative codes to points. | |
| """ | |
| if copy: | |
| rel_points = rel_points.copy() | |
| if self.stddevs: | |
| rel_points[..., 0::2] *= self.stddevs[0] | |
| rel_points[..., 1::2] *= self.stddevs[1] | |
| rel_points[..., 0::2] *= reference_boxes[..., 2:3] | |
| rel_points[..., 1::2] *= reference_boxes[..., 3:4] | |
| rel_points[..., 0::2] += reference_boxes[..., 0:1] | |
| rel_points[..., 1::2] += reference_boxes[..., 1:2] | |
| return rel_points | |