YOLO算法改进4【中阶改进篇】：添加DeformableConvolution v2可变形卷积模块

news2024/11/23 21:25:55

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论文地址： https://arxiv.org/abs/1811.11168
源码地址：https://github.com/msracver/Deformable-ConvNets

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传统的卷积操作是将特征图分成一个个与卷积核大小相同的部分，然后进行卷积操作，每部分在特征图上的位置都是固定的。这样，对于形变比较复杂的物体，使用这种卷积的效果就可能不太好了。对于这种情况，传统做法有丰富数据集，引入更多复杂形变的样本、使用各种数据增强和trick，以及人工设计一些手工特征和算法。
基于数据集和数据增强的做法都有点“暴力”，通常收敛慢而且需要较复杂的网络结构来配合；而基于手工特征算法就实在是有点“太难了”。特变是物体形变可能千变万化，这种做法本身难度就很大，而且不灵活。这时候，Deformable Conv 出道了！他站上演讲台，说他是个性boy，他会变形，不像常规卷积那样死板，他更灵活，可以应对上述提到的物体复杂形变的场景。

1.增加 DCnv2文件
添加至/models/文件中

# parameters
nc: 80  # number of classes
depth_multiple: 0.33  # model depth multiple
width_multiple: 0.50  # layer channel multiple
 
# anchors
anchors:
  - [10,13, 16,30, 33,23]  # P3/8
  - [30,61, 62,45, 59,119]  # P4/16
  - [116,90, 156,198, 373,326]  # P5/32
 
# YOLOv5 v6.0 backbone
  backbone:
  # [from, number, module, args]
  [[-1, 1, Conv, [64, 6, 2, 2]],  # 0-P1/2
   [-1, 1, DCnv2, [128, 3, 2]],  # 1-P2/4  [32,64,3,2]
   [-1, 3, C3, [128]],                   #[64,64,1]
   [-1, 1, DCnv2, [256, 3, 2]],  # 3-P3/8  [64,128,3,2]
   [-1, 6, C3, [256]],                   #[128,128,2]
   [-1, 1, DCnv2, [512, 3, 2]],  # 5-P4/16 #[128,256,3,2]
   [-1, 9, C3, [512]],                     #[256,256,3]
   [-1, 1, Conv, [1024, 3, 2]],  # 7-P5/32 #[256,512,3,2]
   [-1, 3, C3, [1024]],  # 9
   [-1, 1, SPPF, [1024, 5]],
  ]
# YOLOv5 v6.0 head
head:
  [[-1, 1, Conv, [512, 1, 1]],
   [-1, 1, nn.Upsample, [None, 2, 'nearest']],
   [[-1, 6], 1, Concat, [1]],  # cat backbone P4
   [-1, 3, C3, [512, False]],  # 13
 
   [-1, 1, Conv, [256, 1, 1]],
   [-1, 1, nn.Upsample, [None, 2, 'nearest']],
   [[-1, 4], 1, Concat, [1]],  # cat backbone P3
   [-1, 3, C3, [256, False]],  # 17 (P3/8-small)
 
   [-1, 1, Conv, [256, 3, 2]],
   [[-1, 14], 1, Concat, [1]],  # cat head P4
   [-1, 3, C3, [512, False]],  # 20 (P4/16-medium)
 
   [-1, 1, Conv, [512, 3, 2]],
   [[-1, 10], 1, Concat, [1]],  # cat head P5
   [-1, 3, C3, [1024, False]],  # 23 (P5/32-large)
 
   [[17, 20, 23], 1, Detect, [nc, anchors]],  # Detect(P3, P4, P5)
  ]

2.common.py配置
在./models/common.py文件中增加以下模板代码

from torchvision.ops import DeformConv2d  # 导入模块

class DCnv2(nn.Module):
    def __init__(self, c1, c2, k=3, s=1, p=1, g=1, act=True):
        super(DCnv2, self).__init__()
        self.conv1 = nn.Conv2d(c1, c2, kernel_size=k, stride=1, padding=p, groups=g, bias=False)
        deformable_groups = 1
        offset_channels = 18
        mask_channels = 9
        self.conv2_offset = nn.Conv2d(c2, deformable_groups * offset_channels, kernel_size=k, stride=s, padding=p)
        self.conv2_mask = nn.Conv2d(c2, deformable_groups*mask_channels, kernel_size=k, stride=s, padding=p)
        # init_mask = torch.Tensor(np.zeros([mask_channels, 3, 3, 3])) + np.array([0.5])
        # self.conv2_mask.weight = torch.nn.Parameter(init_mask)
        self.conv2 = DeformConv2d(c2, c2, kernel_size=k, stride=s, padding=1, bias=True)
 
        self.bn1 = nn.BatchNorm2d(c2)
        self.act1 = nn.SiLU() if act is True else (act if isinstance(act, nn.Module) else nn.Identity())
        self.bn2 = nn.BatchNorm2d(c2)
        self.act2 = nn.SiLU() if act is True else (act if isinstance(act, nn.Module) else nn.Identity())
 
    def forward(self, x):
        x = self.act1(self.bn1(self.conv1(x)))
        offset = self.conv2_offset(x)
        mask = torch.sigmoid(self.conv2_mask(x))
        x = self.act2(self.bn2(self.conv2(x, offset=offset, mask=mask)))
 
        return x

3.yolo.py配置
找到 models/yolo.py 文件中 parse_model() 图数的对DCnv2类进行声明。DCnv2声明的位置如下图所示。

if m in {
                Conv, GhostConv, Bottleneck, GhostBottleneck, SPP, SPPF, DWConv, MixConv2d, Focus, CrossConv,
                BottleneckCSP, C3, C3TR, C3SPP, C3Ghost, nn.ConvTranspose2d, DWConvTranspose2d, C3x,DCnv2 }: