Pytorch：搭建卷积神经网络完成MNIST分类任务：-Toy模板网

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2023.7.18

MNIST百科：

MNIST数据集简介与使用_bwqiang的博客-CSDN博客

数据集官网：MNIST handwritten digit database, Yann LeCun, Corinna Cortes and Chris Burges

MNIST数据集获取并转换成图片格式：

数据集将按以图片和文件夹名为标签的形式保存：

Pytorch：搭建卷积神经网络完成MNIST分类任务：,pytorch,cnn,分类

代码：下载mnist数据集并转还为图片


import os
from PIL import Image
from torchvision import datasets, transforms

# 定义数据转换
transform = transforms.Compose([
    transforms.ToTensor(),  # 转换为张量
    transforms.Normalize((0.5,), (0.5,))  # 标准化
])

# 下载并加载训练集和测试集
train_dataset = datasets.MNIST(root=os.getcwd(), train=True, transform=transform, download=True)
test_dataset = datasets.MNIST(root=os.getcwd(), train=False, transform=transform, download=True)

# 路径
train_path = './images/train'
test_path = './images/test'

# 将训练集中的图像保存为图片
for i in range(10):
    file_name = train_path + os.sep + str(i)
    if not os.path.exists(file_name):
        os.mkdir(file_name)

for i in range(10):
    file_name = test_path + os.sep + str(i)
    if not os.path.exists(file_name):
        os.mkdir(file_name)

for i, (image, label) in enumerate(train_dataset):
    train_label = label
    image_path = f'images/train/{train_label}/{i}.png'
    image = image.squeeze().numpy()  # 去除通道维度，并转换为 numpy 数组
    image = (image * 0.5) + 0.5  # 反标准化，将范围调整为 [0, 1]
    image = (image * 255).astype('uint8')  # 将范围调整为 [0, 255]，并转换为整数类型
    Image.fromarray(image).save(image_path)

# 将测试集中的图像保存为图片
for i, (image, label) in enumerate(test_dataset):
    text_label = label
    image_path = f'images/test/{text_label}/{i}.png'
    image = image.squeeze().numpy()  # 去除通道维度，并转换为 numpy 数组
    image = (image * 0.5) + 0.5  # 反标准化，将范围调整为 [0, 1]
    image = (image * 255).astype('uint8')  # 将范围调整为 [0, 255]，并转换为整数类型
    Image.fromarray(image).save(image_path)

训练代码：


import os
import torch
import torch.nn as nn
import torch.optim as optim
import numpy as np
import torchvision.transforms as transforms
from PIL import Image

# 调动显卡进行计算
device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")


class MyDataset(torch.utils.data.Dataset):
    def __init__(self, root_dir, transform=None):
        self.root_dir = root_dir
        self.transform = transform
        self.names_list = []

        for dirs in os.listdir(self.root_dir):
            dir_path = self.root_dir + '/' + dirs
            for imgs in os.listdir(dir_path):
                img_path = dir_path + '/' + imgs
                self.names_list.append((img_path, dirs))

    def __len__(self):
        return len(self.names_list)

    def __getitem__(self, index):
        image_path, label = self.names_list[index]
        if not os.path.isfile(image_path):
            print(image_path + '不存在该路径')
            return None
        image = Image.open(image_path)

        label = np.array(label).astype(int)
        label = torch.from_numpy(label)

        if self.transform:
            image = self.transform(image)

        return image, label


# 定义卷积神经网络模型
class CNN(nn.Module):
    def __init__(self):
        super(CNN, self).__init__()
        self.conv1 = nn.Conv2d(1, 16, kernel_size=3, stride=1, padding=1)
        self.relu = nn.ReLU()
        self.maxpool = nn.MaxPool2d(kernel_size=2, stride=2)
        self.fc = nn.Linear(16 * 14 * 14, 10)

    def forward(self, x):
        x = self.conv1(x)  # 卷积
        x = self.relu(x)  # 激活函数
        x = self.maxpool(x)  # 最大值池化
        x = x.view(x.size(0), -1)
        x = self.fc(x)  # 全连接层
        return x


# 加载手写数字数据集
train_dataset = MyDataset('./dataset/images/train', transform=transforms.ToTensor())
val_dataset = MyDataset('./dataset/images/val', transform=transforms.ToTensor())

# 定义超参数
batch_size = 8192  # 批处理大小
learning_rate = 0.001  # 学习率
num_epochs = 30  # 迭代次数

# 创建数据加载器
train_loader = torch.utils.data.DataLoader(dataset=train_dataset, batch_size=batch_size, shuffle=True)
val_loader = torch.utils.data.DataLoader(dataset=val_dataset, batch_size=batch_size, shuffle=False)

# 实例化模型、损失函数和优化器
model = CNN().to(device)
criterion = nn.CrossEntropyLoss()  # 损失函数
optimizer = optim.Adam(model.parameters(), lr=learning_rate)  # 优化器

# 记录验证的次数
total_train_step = 0
total_val_step = 0

# 模型训练和验证
print("-------------TRAINING-------------")
total_step = len(train_loader)
for epoch in range(num_epochs):
    print("Epoch=", epoch)
    for i, (images, labels) in enumerate(train_loader):
        images = images.to(device)
        labels = labels.to(device)
        output = model(images)
        loss = criterion(output, labels.long())

        optimizer.zero_grad()
        loss.backward()
        optimizer.step()

        total_train_step = total_train_step + 1
        print("train_times:{},Loss:{}".format(total_train_step, loss.item()))

    # 测试验证
    total_val_loss = 0
    total_accuracy = 0
    with torch.no_grad():
        for i, (images, labels) in enumerate(val_loader):
            images = images.to(device)
            labels = labels.to(device)
            outputs = model(images)
            loss = criterion(outputs, labels.long())

            total_val_loss = total_val_loss + loss.item()  # 计算损失值的和
            accuracy = 0

            for j in labels:  # 计算精确度的和
                if outputs.argmax(1)[j] == labels[j]:
                    accuracy = accuracy + 1

            total_accuracy = total_accuracy + accuracy

    print('Accuracy =', float(total_accuracy / len(val_dataset)))  # 输出正确率
    torch.save(model, "cnn_{}.pth".format(epoch))  # 模型保存

# # 模型评估
# with torch.no_grad():
#     correct = 0
#     total = 0
#     for images, labels in test_loader:
#         outputs = model(images)
#         _, predicted = torch.max(outputs.data, 1)
#         total += labels.size(0)
#         correct += (predicted == labels).sum().item()

测试代码：

import torch
from torchvision import transforms
import torch.nn as nn
import os
from PIL import Image

device = torch.device('cuda:0' if torch.cuda.is_available() else 'cpu')  # 判断是否有GPU


class CNN(nn.Module):
    def __init__(self):
        super(CNN, self).__init__()
        self.conv1 = nn.Conv2d(1, 16, kernel_size=3, stride=1, padding=1)
        self.relu = nn.ReLU()
        self.maxpool = nn.MaxPool2d(kernel_size=2, stride=2)
        self.fc = nn.Linear(16 * 14 * 14, 10)

    def forward(self, x):
        x = self.conv1(x)  # 卷积
        x = self.relu(x)  # 激活函数
        x = self.maxpool(x)  # 最大值池化
        x = x.view(x.size(0), -1)
        x = self.fc(x)  # 全连接层
        return x


model = torch.load('cnn.pth')  # 加载模型

path = "./dataset/images/test/"  # 测试集

imgs = os.listdir(path)

test_num = len(imgs)
print(f"test_dataset_quantity={test_num}")

for img_name in imgs:
    img = Image.open(path + img_name)

    test_transform = transforms.Compose([transforms.ToTensor()])

    img = test_transform(img)
    img = img.to(device)
    img = img.unsqueeze(0)
    outputs = model(img)  # 将图片输入到模型中
    _, predicted = outputs.max(1)

    pred_type = predicted.item()
    print(img_name, 'pred_type:', pred_type)

分类正确率不错：

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