28-目标检测

import torch
import matplotlib.pyplot as plt
from sympy.physics.control.control_plots import matplotlib

from d2l import torch as d2l

# plt.figure(figsize=(3.5, 2.5))
img = d2l.plt.imread('./image/catdog.jpg')
# plt.imshow(img)
# plt.show()

def box_corner_to_center(boxes):
    x1, y1, x2, y2 = boxes[:, 0], boxes[:, 1], boxes[:, 2], boxes[:, 3]
    cx = (x1 + x2) / 2
    cy = (y1 + y2) / 2
    w = x2 - x1
    h = y2 - y1
    boxes = torch.stack([cx, cy, w, h], axis=-1)

    return boxes

def box_center_to_corner(boxes):
    """从（中间，宽度，高度）转换到（左上，右下）"""
    cx, cy, w, h = boxes[:, 0], boxes[:, 1], boxes[:, 2], boxes[:, 3]
    x1 = cx - 0.5 * w
    y1 = cy - 0.5 * h
    x2 = cx + 0.5 * w
    y2 = cy + 0.5 * h
    boxes = torch.stack((x1, y1, x2, y2), axis=1)
    return boxes

dog_bbox, cat_bbox = [60.0, 45.0, 378.0, 516.0], [400.0, 112.0, 655.0, 493.0]

boxes = torch.tensor((dog_bbox, cat_bbox))
print(box_center_to_corner(box_corner_to_center(boxes)) == boxes)
print(box_center_to_corner(box_corner_to_center(boxes)))

def bbox_to_rect(bbox, color):
    return d2l.plt.Rectangle(xy=(bbox[0], bbox[1]), width = bbox[2] - bbox[0], height=bbox[3] - bbox[1], fill=False, edgecolor=color)

fig = d2l.plt.imshow(img)
fig.axes.add_patch(bbox_to_rect(dog_bbox, 'blue'))
fig.axes.add_patch(bbox_to_rect(cat_bbox, 'red'))