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Python打卡训练营学习记录Day43

article 2025/8/20 12:26:02

作业：

kaggle找到一个图像数据集，用cnn网络进行训练并且用grad-cam做可视化

进阶：并拆分成多个文件

从谷歌图片中拍摄的 10 种不同类别的动物图片

数据预处理

import os
from torchvision import datasets, transforms
from torch.utils.data import DataLoader, random_splitdef load_data(data_dir, batch_size):# 数据预处理data_transform = transforms.Compose([transforms.RandomResizedCrop(224),transforms.RandomHorizontalFlip(),transforms.ToTensor(),transforms.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225])])# 加载数据集image_dataset = datasets.ImageFolder(data_dir, data_transform)# 划分训练集和验证集train_size = int(0.8 * len(image_dataset))val_size = len(image_dataset) - train_sizetrain_dataset, val_dataset = random_split(image_dataset, [train_size, val_size])train_dataloader = DataLoader(train_dataset, batch_size=batch_size, shuffle=True, num_workers=4)val_dataloader = DataLoader(val_dataset, batch_size=batch_size, shuffle=False, num_workers=4)dataloaders = {'train': train_dataloader, 'val': val_dataloader}dataset_sizes = {'train': train_size, 'val': val_size}class_names = image_dataset.classesreturn dataloaders, dataset_sizes, class_names

构建并训练 CNN 模型

import torch.nn as nnclass SimpleCNN(nn.Module):def __init__(self, num_classes):super(SimpleCNN, self).__init__()# 定义特征提取层self.features = nn.Sequential(nn.Conv2d(3, 16, kernel_size=3, padding=1),nn.ReLU(inplace=True),nn.MaxPool2d(kernel_size=2, stride=2),nn.Conv2d(16, 32, kernel_size=3, padding=1),nn.ReLU(inplace=True),nn.MaxPool2d(kernel_size=2, stride=2),nn.Conv2d(32, 64, kernel_size=3, padding=1),nn.ReLU(inplace=True),nn.MaxPool2d(kernel_size=2, stride=2))# 定义分类层self.classifier = nn.Sequential(nn.Linear(64 * 28 * 28, 512),nn.ReLU(inplace=True),nn.Linear(512, num_classes))def forward(self, x):# 前向传播，先通过特征提取层，再通过分类层x = self.features(x)x = x.view(-1, 64 * 28 * 28)x = self.classifier(x)return x

模型训练模块

import torch
import torch.nn as nn
import torch.optim as optimdef train_model(model, dataloaders, dataset_sizes, criterion, optimizer, num_epochs=25):# 判断是否有可用的 GPU，若有则使用 GPU 进行训练device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")model.to(device)for epoch in range(num_epochs):print(f'第 {epoch} 个 epoch，共 {num_epochs - 1} 个 epochs')print('-' * 10)# 每个 epoch 都有一个训练和验证阶段for phase in ['train', 'val']:if phase == 'train':model.train()  # 训练模式else:model.eval()   # 评估模式running_loss = 0.0running_corrects = 0# 迭代数据for inputs, labels in dataloaders[phase]:inputs = inputs.to(device)labels = labels.to(device)# 零参数梯度optimizer.zero_grad()# 前向传播# 只有在训练时才跟踪历史with torch.set_grad_enabled(phase == 'train'):outputs = model(inputs)_, preds = torch.max(outputs, 1)loss = criterion(outputs, labels)# 只有在训练阶段才进行反向传播和优化if phase == 'train':loss.backward()optimizer.step()# 统计running_loss += loss.item() * inputs.size(0)running_corrects += torch.sum(preds == labels.data)epoch_loss = running_loss / dataset_sizes[phase]epoch_acc = running_corrects.double() / dataset_sizes[phase]print(f'{phase} 阶段：损失值: {epoch_loss:.4f} 准确率: {epoch_acc:.4f}')return model

Grad-CAM可视化模块

import torch
import torch.nn.functional as F
import numpy as np
import cv2class GradCAM:def __init__(self, model, target_layer):self.model = modelself.target_layer = target_layerself.gradients = Noneself.activations = None# 反向传播钩子函数，用于捕获梯度def backward_hook(module, grad_input, grad_output):self.gradients = grad_output[0]# 前向传播钩子函数，用于捕获激活值def forward_hook(module, input, output):self.activations = outputtarget_layer.register_forward_hook(forward_hook)target_layer.register_backward_hook(backward_hook)def forward(self, input_tensor):# 将模型设置为评估模式并进行前向传播self.model.eval()output = self.model(input_tensor)return outputdef generate_cam(self, input_tensor, target_class=None):# 进行前向传播output = self.forward(input_tensor)# 如果未指定目标类别，则选择输出概率最大的类别if target_class is None:target_class = torch.argmax(output, dim=1).item()one_hot = torch.zeros_like(output)one_hot[:, target_class] = 1one_hot.requires_grad_(True)# 清零模型参数的梯度self.model.zero_grad()# 计算损失并进行反向传播(one_hot * output).sum().backward(retain_graph=True)gradients = self.gradients[0]activations = self.activations[0]# 对梯度进行全局平均池化pooled_gradients = torch.mean(gradients, dim=[1, 2])for i in range(activations.shape[0]):activations[i, :, :] *= pooled_gradients[i]# 对激活值求和生成 CAM 图cam = torch.sum(activations, dim=0).detach().cpu().numpy()# 取 CAM 图的正值部分cam = np.maximum(cam, 0)# 调整 CAM 图的大小以匹配输入图像cam = cv2.resize(cam, (input_tensor.shape[3], input_tensor.shape[2]))# 归一化 CAM 图cam = cam - np.min(cam)cam = cam / np.max(cam)return cam

主程序

from data_loader import load_data
from model import SimpleCNN
from train import train_model
from grad_cam import GradCAM
import torch
import torch.nn as nn
import torch.optim as optim
from torchvision import transforms
from PIL import Image
import numpy as np
import cv2
import sys
import os
# 将当前目录添加到 Python 模块搜索路径中
sys.path.append(os.path.dirname(os.path.abspath(__file__)))if __name__ == '__main__':# 加载数据，设置批次大小，你可以根据需要调整该值batch_size = 32# 修改解包操作以处理所有返回值dataloaders, dataset_sizes, class_names = load_data('raw-img', batch_size)# 获取类别数量num_classes = len(class_names)# 使用类别数量初始化模型model = SimpleCNN(num_classes)# 定义损失函数和优化器criterion = nn.CrossEntropyLoss()optimizer = optim.SGD(model.parameters(), lr=0.001, momentum=0.9)# 训练模型trained_model = train_model(model, dataloaders, dataset_sizes, criterion, optimizer, num_epochs=5)# 生成 Grad - CAM 可视化结果# 修改此处，选择实际存在的卷积层# grad_cam = GradCAM(model, target_layer=model.conv2)grad_cam = GradCAM(model, target_layer=model.features[0])img_path = 'path/to/your/image.jpg'img = Image.open(img_path).convert('RGB')cam = grad_cam(img)plt.imshow(img)plt.imshow(cam, alpha=0.5, cmap='jet')plt.axis('off')plt.savefig('grad_cam_result.jpg')plt.show()

@浙大疏锦行

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