目标检测和边界框

代维7

于 2022-07-16 19:29:10 发布

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分类专栏：深度学习文章标签：目标检测深度学习 pytorch

本文链接：https://blog.youkuaiyun.com/Recursions/article/details/125823682

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这段代码展示了如何将图像中的边界框从左上和右下坐标转换为中间点和宽高，以及反之。它还提供了用于在图像上绘制边界框的辅助函数。示例应用在'catdog.jpg'图片上，用蓝色和红色分别标记了狗和猫的边界框。

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import torch
from d2l import torch as d2l

d2l.set_figsize()
img = d2l.plt.imread('./catdog.jpg')
d2l.plt.imshow(img)

#@save
def box_corner_to_center(boxes):
    """从左上右下到中间宽和高"""
    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

#@save
def box_center_to_corner(boxes):
    """从中间宽高到左上右下"""
    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))

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,linewidth = 2
    )

img = d2l.plt.imread('./catdog.jpg')
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'))