YOLOv11改进 | 添加注意力篇 | 一文带你改进GAM、CBAM、CA、ECA等通道注意力机制和多头注意力机制

import torch
import torch.nn as nn
 
'''
https://arxiv.org/abs/2112.05561
'''
 
class GAM(nn.Module):
    def __init__(self, in_channels, rate=4):
        super().__init__()
        out_channels = in_channels
        in_channels = int(in_channels)
        out_channels = int(out_channels)
        inchannel_rate = int(in_channels/rate)
 
 
        self.linear1 = nn.Linear(in_channels, inchannel_rate)
        self.relu = nn.ReLU(inplace=True)
        self.linear2 = nn.Linear(inchannel_rate, in_channels)
        
 
        self.conv1=nn.Conv2d(in_channels, inchannel_rate,kernel_size=7,padding=3,padding_mode='replicate')
 
        self.conv2=nn.Conv2d(inchannel_rate, out_channels,kernel_size=7,padding=3,padding_mode='replicate')
 
        self.norm1 = nn.BatchNorm2d(inchannel_rate)
        self.norm2 = nn.BatchNorm2d(out_channels)
        self.sigmoid = nn.Sigmoid()
 
    def forward(self,x):
        b, c, h, w = x.shape
        # B,C,H,W ==> B,H*W,C
        x_permute = x.permute(0, 2, 3, 1).view(b, -1, c)
        
        # B,H*W,C ==> B,H,W,C
        x_att_permute = self.linear2(self.relu(self.linear1(x_permute))).view(b, h, w, c)
 
        # B,H,W,C ==> B,C,H,W
        x_channel_att = x_att_permute.permute(0, 3, 1, 2)
 
        x = x * x_channel_att
 
        x_spatial_att = self.relu(self.norm1(self.conv1(x)))
        x_spatial_att = self.sigmoid(self.norm2(self.conv2(x_spatial_att)))
        
        out = x * x_spatial_att
 
        return out
 
if __name__ == '__main__':
    img = torch.rand(1,64,32,48)
    b, c, h, w = img.shape
    net = GAM(in_channels=c, out_channels=c)
    output = net(img)
    print(output.shape)

import torch
import torch.nn as nn
 
 
class ChannelAttention(nn.Module):
    """Channel-attention module https://github.com/open-mmlab/mmdetection/tree/v3.0.0rc1/configs/rtmdet."""
 
    def __init__(self, channels: int) -> None:
        """Initializes the class and sets the basic configurations and instance variables required."""
        super().__init__()
        self.pool = nn.AdaptiveAvgPool2d(1)
        self.fc = nn.Conv2d(channels, channels, 1, 1, 0, bias=True)
        self.act = nn.Sigmoid()
 
    def forward(self, x: torch.Tensor) -> torch.Tensor:
        """Applies forward pass using activation on convolutions of the input, optionally using batch normalization."""
        return x * self.act(self.fc(self.pool(x)))
 
 
class SpatialAttention(nn.Module):
    """Spatial-attention module."""
 
    def __init__(self, kernel_size=7):
        """Initialize Spatial-attention module with kernel size argument."""
        super().__init__()
        assert kernel_size in (3, 7), "kernel size must be 3 or 7"
        padding = 3 if kernel_size == 7 else 1
        self.cv1 = nn.Conv2d(2, 1, kernel_size, padding=padding, bias=False)
        self.act = nn.Sigmoid()
 
    def forward(self, x):
        """Apply channel and spatial attention on input for feature recalibration."""
        return x * self.act(self.cv1(torch.cat([torch.mean(x, 1, keepdim=True), torch.max(x, 1, keepdim=True)[0]], 1)))
 
 
class CBAM(nn.Module):
    """Convolutional Block Attention Module."""
 
    def __init__(self, c1, kernel_size=7):
        """Initialize CBAM with given input channel (c1) and kernel size."""
        super().__init__()
        self.channel_attention = ChannelAttention(c1)
        self.spatial_attention = SpatialAttention(kernel_size)
 
    def forward(self, x):
        """Applies the forward pass through C1 module."""
        return self.spatial_attention(self.channel_attention(x))

import torch
import torch.nn as nn
import math
import torch.nn.functional as F
 
class h_sigmoid(nn.Module):
    def __init__(self, inplace=True):
        super(h_sigmoid, self).__init__()
        self.relu = nn.ReLU6(inplace=inplace)
 
    def forward(self, x):
        return self.relu(x + 3) / 6
 
class h_swish(nn.Module):
    def __init__(self, inplace=True):
        super(h_swish, self).__init__()
        self.sigmoid = h_sigmoid(inplace=inplace)
 
    def forward(self, x):
        return x * self.sigmoid(x)
 
class CoordAtt(nn.Module):
    def __init__(self, inp, reduction=32):
        super(CoordAtt, self).__init__()
        oup = inp
        self.pool_h = nn.AdaptiveAvgPool2d((None, 1))
        self.pool_w = nn.AdaptiveAvgPool2d((1, None))
 
        mip = max(8, inp // reduction)
 
        self.conv1 = nn.Conv2d(inp, mip, kernel_size=1, stride=1, padding=0)
        self.bn1 = nn.BatchNorm2d(mip)
        self.act = h_swish()
        
        self.conv_h = nn.Conv2d(mip, oup, kernel_size=1, stride=1, padding=0)
        self.conv_w = nn.Conv2d(mip, oup, kernel_size=1, stride=1, padding=0)
        
 
    def forward(self, x):
        identity = x
        
        n,c,h,w = x.size()
        x_h = self.pool_h(x)
        x_w = self.pool_w(x).permute(0, 1, 3, 2)
 
        y = torch.cat([x_h, x_w], dim=2)
        y = self.conv1(y)
        y = self.bn1(y)
        y = self.act(y) 
        
        x_h, x_w = torch.split(y, [h, w], dim=2)
        x_w = x_w.permute(0, 1, 3, 2)
 
        a_h = self.conv_h(x_h).sigmoid()
        a_w = self.conv_w(x_w).sigmoid()
 
        out = identity * a_w * a_h
 
        return out

import torch
from torch import nn
from torch.nn.parameter import Parameter
 
class ECA(nn.Module):
    """Constructs a ECA module.
    Args:
        channel: Number of channels of the input feature map
        k_size: Adaptive selection of kernel size
    """
    def __init__(self, channel, k_size=3):
        super(ECA, self).__init__()
        self.avg_pool = nn.AdaptiveAvgPool2d(1)
        self.conv = nn.Conv1d(1, 1, kernel_size=k_size, padding=(k_size - 1) // 2, bias=False) 
        self.sigmoid = nn.Sigmoid()
 
    def forward(self, x):
        # feature descriptor on the global spatial information
        y = self.avg_pool(x)
 
        # Two different branches of ECA module
        y = self.conv(y.squeeze(-1).transpose(-1, -2)).transpose(-1, -2).unsqueeze(-1)
 
        # Multi-scale information fusion
        y = self.sigmoid(y)
 
        return x * y.expand_as(x)

# Ultralytics YOLO 🚀, AGPL-3.0 license
# YOLO11 object detection model with P3-P5 outputs. For Usage examples see https://docs.ultralytics.com/tasks/detect
 
# Parameters
nc: 80 # number of classes
scales: # model compound scaling constants, i.e. 'model=yolo11n.yaml' will call yolo11.yaml with scale 'n'
  # [depth, width, max_channels]
  n: [0.50, 0.25, 1024] # summary: 319 layers, 2624080 parameters, 2624064 gradients, 6.6 GFLOPs
  s: [0.50, 0.50, 1024] # summary: 319 layers, 9458752 parameters, 9458736 gradients, 21.7 GFLOPs
  m: [0.50, 1.00, 512] # summary: 409 layers, 20114688 parameters, 20114672 gradients, 68.5 GFLOPs
  l: [1.00, 1.00, 512] # summary: 631 layers, 25372160 parameters, 25372144 gradients, 87.6 GFLOPs
  x: [1.00, 1.50, 512] # summary: 631 layers, 56966176 parameters, 56966160 gradients, 196.0 GFLOPs
 
# YOLO11n backbone
backbone:
  # [from, repeats, module, args]
  - [-1, 1, Conv, [64, 3, 2]] # 0-P1/2
  - [-1, 1, Conv, [128, 3, 2]] # 1-P2/4
  - [-1, 2, C3k2, [256, False, 0.25]]
  - [-1, 1, Conv, [256, 3, 2]] # 3-P3/8
  - [-1, 2, C3k2, [512, False, 0.25]]
  - [-1, 1, Conv, [512, 3, 2]] # 5-P4/16
  - [-1, 2, C3k2, [512, True]]
  - [-1, 1, Conv, [1024, 3, 2]] # 7-P5/32
  - [-1, 2, C3k2, [1024, True]]
  - [-1, 1, SPPF, [1024, 5]] # 9
  - [-1, 2, C2PSA, [1024]] # 10
 
# YOLO11n head
head:
  - [-1, 1, nn.Upsample, [None, 2, "nearest"]]
  - [[-1, 6], 1, Concat, [1]] # cat backbone P4
  - [-1, 2, C3k2, [512, False]] # 13
 
  - [-1, 1, nn.Upsample, [None, 2, "nearest"]]
  - [[-1, 4], 1, Concat, [1]] # cat backbone P3
  - [-1, 2, C3k2, [256, False]] # 16 (P3/8-small)
 
  - [-1, 1, Conv, [256, 3, 2]]
  - [[-1, 13], 1, Concat, [1]] # cat head P4
  - [-1, 2, C3k2, [512, False]] # 19 (P4/16-medium)
 
  - [-1, 1, Conv, [512, 3, 2]]
  - [[-1, 10], 1, Concat, [1]] # cat head P5
  - [-1, 2, C3k2, [1024, True]] # 22 (P5/32-large)
  - [-1, 1, CBAM, []]  # 23 这里默认先用的CBAM大家使用那个只需要把其他的注释掉即可，这里是在大目标检测曾层输出位置添加一个注意力机制。
  #  - [-1, 1, ECA, []]  # 23
  #  - [-1, 1, GAM, []]  # 23
  #  - [-1, 1, CoordAtt, []]  # 23
  - [[16, 19, 23], 1, Detect, [nc]] # Detect(P3, P4, P5)