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| #!/usr/bin/python | |
| # | |
| # Copyright 2018 Google LLC | |
| # | |
| # 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 | |
| # limitations under the License. | |
| import torch | |
| """ | |
| Utilities for dealing with bounding boxes | |
| """ | |
| def box_abs2rel(boxes, inside_boxes, obj_to_img): | |
| inside_boxes = inside_boxes[obj_to_img] | |
| ix0, iy0, ix1, iy1 = inside_boxes[:, 0], inside_boxes[:, 1], inside_boxes[:, 2], inside_boxes[:, 3] | |
| xc = (boxes[:, 0] - ix0) / (ix1 - ix0) | |
| yc = (boxes[:, 1] - iy0) / (iy1 - iy0) | |
| w = boxes[:, 2] / (ix1 - ix0) | |
| h = boxes[:, 3] / (iy1 - iy0) | |
| return torch.stack([xc, yc, w, h], dim=1) | |
| def box_rel2abs(boxes, inside_boxes, obj_to_img): | |
| inside_boxes = inside_boxes[obj_to_img] | |
| ix0, iy0, ix1, iy1 = inside_boxes[:, 0], inside_boxes[:, 1], inside_boxes[:, 2], inside_boxes[:, 3] | |
| xc = boxes[:, 0] * (ix1 - ix0) + ix0 | |
| yc = boxes[:, 1] * (iy1 - iy0) + iy0 | |
| w = boxes[:, 2] * (ix1 - ix0) | |
| h = boxes[:, 3] * (iy1 - iy0) | |
| return torch.stack([xc, yc, w, h], dim=1) | |
| def norms_to_indices(boxes,H,W=None): | |
| if W is None: | |
| W=H | |
| x0,x1 = boxes[:,0]*(W-1),boxes[:,2]*(W-1)+1 | |
| y0,y1 = boxes[:,1]*(H-1),boxes[:,3]*(H-1)+1 | |
| return torch.stack([x0, y0, x1, y1], dim=1).round().long() | |
| def apply_box_transform(anchors, transforms): | |
| """ | |
| Apply box transforms to a set of anchor boxes. | |
| Inputs: | |
| - anchors: Anchor boxes of shape (N, 4), where each anchor is specified | |
| in the form [xc, yc, w, h] | |
| - transforms: Box transforms of shape (N, 4) where each transform is | |
| specified as [tx, ty, tw, th] | |
| Returns: | |
| - boxes: Transformed boxes of shape (N, 4) where each box is in the | |
| format [xc, yc, w, h] | |
| """ | |
| # Unpack anchors | |
| xa, ya = anchors[:, 0], anchors[:, 1] | |
| wa, ha = anchors[:, 2], anchors[:, 3] | |
| # Unpack transforms | |
| tx, ty = transforms[:, 0], transforms[:, 1] | |
| tw, th = transforms[:, 2], transforms[:, 3] | |
| x = xa + tx * wa | |
| y = ya + ty * ha | |
| w = wa * tw.exp() | |
| h = ha * th.exp() | |
| boxes = torch.stack([x, y, w, h], dim=1) | |
| return boxes | |
| def invert_box_transform(anchors, boxes): | |
| """ | |
| Compute the box transform that, when applied to anchors, would give boxes. | |
| Inputs: | |
| - anchors: Box anchors of shape (N, 4) in the format [xc, yc, w, h] | |
| - boxes: Target boxes of shape (N, 4) in the format [xc, yc, w, h] | |
| Returns: | |
| - transforms: Box transforms of shape (N, 4) in the format [tx, ty, tw, th] | |
| """ | |
| # Unpack anchors | |
| xa, ya = anchors[:, 0], anchors[:, 1] | |
| wa, ha = anchors[:, 2], anchors[:, 3] | |
| # Unpack boxes | |
| x, y = boxes[:, 0], boxes[:, 1] | |
| w, h = boxes[:, 2], boxes[:, 3] | |
| tx = (x - xa) / wa | |
| ty = (y - ya) / ha | |
| tw = w.log() - wa.log() | |
| th = h.log() - ha.log() | |
| transforms = torch.stack([tx, ty, tw, th], dim=1) | |
| return transforms | |
| def centers_to_extents(boxes): | |
| """ | |
| Convert boxes from [xc, yc, w, h] format to [x0, y0, x1, y1] format | |
| Input: | |
| - boxes: Input boxes of shape (N, 4) in [xc, yc, w, h] format | |
| Returns: | |
| - boxes: Output boxes of shape (N, 4) in [x0, y0, x1, y1] format | |
| """ | |
| xc, yc = boxes[:, 0], boxes[:, 1] | |
| w, h = boxes[:, 2], boxes[:, 3] | |
| x0 = xc - w / 2 | |
| x1 = x0 + w | |
| y0 = yc - h / 2 | |
| y1 = y0 + h | |
| boxes_out = torch.stack([x0, y0, x1, y1], dim=1) | |
| return boxes_out | |
| def extents_to_centers(boxes): | |
| """ | |
| Convert boxes from [x0, y0, x1, y1] format to [xc, yc, w, h] format | |
| Input: | |
| - boxes: Input boxes of shape (N, 4) in [x0, y0, x1, y1] format | |
| Returns: | |
| - boxes: Output boxes of shape (N, 4) in [xc, yc, w, h] format | |
| """ | |
| x0, y0 = boxes[:, 0], boxes[:, 1] | |
| x1, y1 = boxes[:, 2], boxes[:, 3] | |
| xc = 0.5 * (x0 + x1) | |
| yc = 0.5 * (y0 + y1) | |
| w = x1 - x0 | |
| h = y1 - y0 | |
| boxes_out = torch.stack([xc, yc, w, h], dim=1) | |
| return boxes_out | |