卷积神经网络实现咖啡豆分类 - P7

• 本文为365天深度学习训练营 中的学习记录博客
• 原作者：K同学啊 | 接辅导、项目定制
• 文章来源：K同学的学习圈子

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环境

• 系统: Linux
• 语言: Python3.8.10
• 深度学习框架: Pytorch2.0.0+cu118
• 显卡：A5000 24G

步骤

环境设置

包引用

import torch
import torch.nn as nn # 网络
import torch.optim as optim # 优化器
from torch.utils.data import DataLoader, random_split # 数据集划分
from torchvision import datasets, transforms # 数据集加载，转换

import pathlib, random, copy # 文件夹遍历，实现模型深拷贝
from PIL import Image # python自带的图像类
import matplotlib.pyplot as plt # 图表
import numpy as np 
from torchinfo import summary # 打印模型参数

全局设备对象

方便将模型和数据统一拷贝到目标设备中

device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')

数据准备

查看图像的信息

data_path = 'coffee_data'
data_lib = pathlib.Path(data_path)
coffee_images = list(data_lib.glob('*/*'))

# 打印5张图像的信息
for _ in range(5):
	image = random.choice(coffee_images)
	print(np.array(Image.open(str(image))).shape)

通过打印的信息，可以看出图像的尺寸都是224x224的，这是一个CV经常使用的图像大小，所以后面我就不使用Resize来缩放图像了。

# 打印20张图像粗略的看一下
plt.figure(figsize=(20, 4))
for i in range(20):
	plt.subplot(2, 10, i+1)
	plt.axis('off')
	image = random.choice(coffee_images) # 随机选出一个图像
	plt.title(image.parts[-2]) # 通过glob对象取出它的文件夹名称，也就是分类名
	plt.imshow(Image.open(str(image))) # 展示

通过展示，对数据集内的图像有个大概的了解

制作数据集

先编写数据的预处理过程，用来使用pytorch的api加载文件夹中的图像

transform = transforms.Compose([
	transforms.ToTensor(), # 先把图像转成张量
	transforms.Normalize( # 对像素值做归一化，将数据范围弄到-1,1
       mean=[0.485, 0.456, 0.406], 
        std=[0.229, 0.224, 0.225],
	),
])

加载文件夹

dataset = datasets.ImageFolder(data_path, transform=transform)

从数据中取所有的分类名

class_names = [k for k in dataset.class_to_idx]
print(class_names)

将数据集划分出训练集和验证集

train_size = int(len(dataset) * 0.8)
test_size = len(dataset) - train_size

train_dataset, test_dataset = random_split(dataset, [train_size, test_size])

将数据集按划分成批次，以便使用小批量梯度下降

batch_size = 32
train_loader = DataLoader(train_dataset, shuffle=True, batch_size=batch_size)
test_loader = DataLoader(test_dataset, batch_size=batch_size)

模型设计

在一开始时，直接手动创建了Vgg-16网络，发现少数几个迭代后模型就收敛了，于是开始精简模型。

手动搭建的vgg16网络

class Vgg16(nn.Module):
	def __init__(self, num_classes):
		super().__init__()
		
		self.block1 = nn.Sequential(
			nn.Conv2d(3, 64, 3, padding=1),
			nn.BatchNorm2d(64),
			nn.ReLU(),
			nn.Conv2d(64, 64, 3, padding=1),
			nn.BatchNorm2d(64),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)
		self.block2 = nn.Sequential(
			nn.Conv2d(64, 128, 3, padding=1),
			nn.BatchNorm2d(128),
			nn.ReLU(),
			nn.Conv2d(128, 128, 3, padding=1),
			nn.BatchNorm2d(128),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)
		self.block3 = nn.Sequential(
			nn.Conv2d(128, 256, 3, padding=1),
			nn.BatchNorm2d(256),
			nn.ReLU(),
			nn.Conv2d(256, 256, 3, padding=1),
			nn.BatchNorm2d(256),
			nn.ReLU(),
			nn.Conv2d(256, 256, 3, padding=1),
			nn.BatchNorm2d(256),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)
		self.block4 = nn.Sequential(
			nn.Conv2d(256, 512, 3, padding=1),
			nn.BatchNorm2d(512),
			nn.ReLU(),
			nn.Conv2d(512, 512, 3, padding=1),
			nn.BatchNorm2d(512),
			nn.ReLU(),
			nn.Conv2d(512, 512, 3, padding=1),
			nn.BatchNorm2d(512),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)
		self.block5 = nn.Sequential(
			nn.Conv2d(512, 512, 3, padding=1),
			nn.BatchNorm2d(512),
			nn.ReLU(),
			nn.Conv2d(512, 512, 3, padding=1),
			nn.BatchNorm2d(512),
			nn.ReLU(),
			nn.Conv2d(512, 512, 3, padding=1),
			nn.BatchNorm2d(512),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)
		self.pool = nn.AdaptiveAvgPool2d(7)
		self.classifier = nn.Sequential(
			nn.Linear(7*7*512, 4096),
			nn.Dropout(0.5),
			nn.ReLU(),
			nn.Linear(4096, 4096),
			nn.Dropout(0.5),
			nn.ReLU(),
			nn.Linear(4096, num_classes),
		)

	def forward(self, x):
		x = self.block1(x)
		x = self.block2(x)
		x = self.block3(x)
		x = self.block4(x)
		x = self.block5(x)
		x = self.pool(x)
		x = x.view(x.size(0),-1)
		x = self.classifier(x)
		return x
vgg = Vgg16(len(class_names)).to(device)
summary(vgg, input_size=(32, 3, 224, 224))

通过模型结构的打印可以发现，VGG-16网络共有134285380个可训练参数（我加了BatchNorm，和官方的比会稍微多出一些），参数量非常巨大，对于咖啡豆识别这种小场景，这么多可训练参数肯定浪费，于是对原始的VGG-16网络结构进行精简。

精简后的咖啡豆识别网络

class Network(nn.Module):
	def __init__(self, num_classes):
		super().__init__()
		
		self.block1 = nn.Sequential(
			nn.Conv2d(3, 64, 3, padding=1),
			nn.BatchNorm2d(64),
			nn.ReLU(),
			nn.Conv2d(64, 64, 3, padding=1),
			nn.BatchNorm2d(64),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)

		self.block2 = nn.Sequential(
			nn.Conv2d(64, 128, 3, padding=1),
			nn.BatchNorm2d(128),
			nn.ReLU(),
			nn.Conv2d(128, 128, 3, padding=1),
			nn.BatchNorm2d(128),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)
		
		self.block3 = nn.Sequential(
			nn.Conv2d(128, 64, 3, padding=1),
			nn.BatchNorm2d(64),
			nn.ReLU(),
			nn.Conv2d(64, 64, 3, padding=1),
			nn.BatchNorm2d(64),
			nn.ReLU(),
			nn.MaxPool2d(2),
		)

		self.pool = nn.AdaptiveAvgPool2d(7),

		self.classifier = nn.Sequential(
			nn.Linear(7*7*64, 64),
			nn.Dropout(0.4),
			nn.ReLU(),
			nn.Linear(64, num_classes)
		)
	
	def forward(self, x):
		x = self.block1(x)
		x = self.block2(x)
		x = self.block3(x)
		x = self.pool(x)
		x = x.view(x.size(0), -1)
		x = self.classifier(x)
		return x
model = Network(len(class_names)).to(device)
summary(model, input_size=(32, 3, 224, 224))

可以看到精简后的网络模型参数量还不到原来的1/10，但是其在测试集上的正确率依然能够达到100%！

模型训练

编写训练函数

def train(train_loader, model, loss_fn, optimizer):
	size = len(train_loader.dataset)
	num_batches = len(train_loader)

	train_loss, train_acc = 0, 0
	for x, y in train_loader:
		x, y = x.to(device), y.to(device)
	
		pred = model(x)
		loss = loss_fn(pred, y)

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

		train_loss += loss.item()
		train_acc += (pred.argmax(1) == y).type(torch.float).sum().item()

	train_loss /= num_batches
	train_acc /= size

	return train_loss, train_acc

编写测试函数

def test(test_loader, model, loss_fn):
	size = len(test_loader.dataset)
	num_batches = len(test_loader)
	
	test_loss, test_acc = 0, 0
	for x, y in test_loader:
		x, y = x.to(device), y.to(device)

		pred = model(x)
		loss = loss_fn(pred, y)

		test_loss += loss.item()
		test_acc += (pred.argmax(1) == y).type(torch.float).sum().item()

	test_loss /= num_batches
	test_acc /= size

	return test_loss, test_acc

开始训练

首先定义损失函数，优化器设置学习率，这里我们再弄一个学习率的衰减，再加上总的迭代次数，最佳模型的保存位置

epochs = 30
loss_fn = nn.CrossEntropyLoss()
optimizer = optim.Adam(model.parameters(), lr=1e-4)
scheduler = optim.lr_scheduler.LambdaLR(optimizer=optimizer, lr_lambda=lambda epoch: 0.92**(epoch//2))
best_model_path = 'best_coffee_model.pth'

然后编写训练+测试的循环，并记录训练过程的数据

best_acc = 0
train_loss, train_acc = [], []
test_loss, test_acc = [], []
for epoch in epochs:
	model.train()
	epoch_train_loss, epoch_train_acc = train(train_loader, model, loss_fn, optimizer)
	scheduler.step()

	model.eval()
	with torch.no_grad();
		epoch_test_loss, epoch_test_acc = test(test_loader, model, loss_fn)
	
	train_loss.append(epoch_train_loss)
	train_acc.append(epoch_train_acc)
	test_loss.append(epoch_test_loss)
	test_acc.append(epoch_test_acc)

	lr = optimizer.state_dict()['param_groups'][0]['lr']

	if best_acc < epoch_test_acc:
		best_acc = epoch_test_acc
		best_model = copy.deepcopy(model)

	print(f"Epoch: {epoch+1}, Lr:{lr}, TrainAcc: {epoch_train_acc*100:.1f}, TrainLoss: {epoch_train_loss:.3f}, TestAcc: {epoch_test_acc*100:.1f}， TestLoss: {epoch_test_loss:.3f}")

print(f"Saving Best Model with Accuracy: {best_acc*100:.1f} to {best_model_path}")
torch.save(best_model.state_dict(), best_model_path)
print('Done')

可以看出，模型在测试集上的正确率最高达到了100%

展示训练过程

epoch_ranges = range(epochs)
plt.figure(figsize=(20,6))
plt.subplot(121)
plt.plot(epoch_ranges, train_loss, label='train loss')
plt.plot(epoch_ranges, test_loss, label='validation loss')
plt.legend(loc='upper right')
plt.title('Loss')

plt.figure(figsize=(20,6))
plt.subplot(122)
plt.plot(epoch_ranges, train_acc, label='train accuracy')
plt.plot(epoch_ranges, test_acc, label='validation accuracy')
plt.legend(loc='lower right')
plt.title('Accuracy')

模型效果展示

model.load_state_dict(torch.load(best_model_path))
model.to(device)
model.eval()

plt.figure(figsize=(20,4))
for i in range(20):
	plt.subplot(2, 10, i+1)
	plt.axis('off')
	image = random.choice(coffee_images)
	input = transform(Image.open(str(image))).to(device).unsqueeze(0)
	pred = model(input)
	plt.title(f'T:{image.parts[-2]}, P:{class_names[pred.argmax()]}')
	plt.imshow(Image.open(str(image)))

通过结果可以看出，确实是所有的咖啡豆都正确的识别了。

总结与心得体会

• 因为目前网络还是很快就收敛到一个很高的水平，所以应该还有很大的精简的空间，但是可能会稍微牺牲一些正确率。
• 模型的选取要根据实际任务来确定，像咖啡豆种类识别这种任务，使用VGG-16太浪费了。
• 在精简的过程中，没有感觉到训练速度有明显的变化 ，说明参数量和训练速度并没有直接的相关关系。
• 连续多层参数一样的卷积操作好像比只用一层效果要好。