模型构建
构建模型为了直观，需要使用 Jupyter notebook 进行模型的构建，Jupyter notebook 的安装及使用详见公众号历史文章 一文吃透 Jupyter Notebook,进入 JupyterNotebook 页面后即可进行编辑。详细页面如下：
导入所需包
图像识别需要用到深度学习相关模块，所以需要导入相应的包，具体导入的包如下：
%reload_ext autoreload %autoreload 2 import torch from torch.utils.data import DataLoader from torchvision.datasets import ImageFolder from torchvision import transforms as tfs from torchvision import models from torch import nn import matplotlib.pyplot as plt %matplotlib inline import os os.environ["KMP_DUPLICATE_LIB_OK"]="TRUE"
是否使用 GPU
模型的训练主要方式是基于 GPU 或者 CPU 训练，在没有 GPU 的条件下就在 CPU 下进行训练，模型的训练需要花费一定的时间，训练时长根据训练集的数据和硬件性能而定，训练结果精确性根据数据的多少和准确性而且，深度学习需要大量的素材才能判断出精确的结果，所以需要申明使用 CPU 进行训练：
# 是否使用GPU use_gpu = False
数据增强
将拿到的数据进行训练集的数据预处理并设置训练分层数，再将拿到的图片进行水平翻转后对图片进行剪裁， 剪裁后将图片进行随机翻转，增强随机对比度以及图片颜色变化
# 数据增强 train_transform = tfs.Compose([ # 训练集的数据预处理 tfs.Resize([224, 224]), tfs.RandomHorizontalFlip(), tfs.RandomCrop(128), tfs.ToTensor(), tfs.Normalize([0.5,0.5,0.5], [0.5,0.5,0.5]) ]) test_transform = tfs.Compose([ tfs.Resize([224,224]), # tfs.RandomCrop(128), tfs.ToTensor(), tfs.Normalize([0.5,0.5,0.5], [0.5,0.5,0.5]) ]) # 每一个batch的数据集数目 batch_size = 10
数据集和验证集准备
模型训练需要准备数据集和验证集，只有足够的照片才能得到更精准的答案。训练集和验证集部分代码如下：
# 构建训练集和验证集 # train_set = ImageFolder('./dataset1/train', train_transform) train_data = DataLoader(train_set, batch_size, shuffle=True, num_workers=0) valid_set = ImageFolder('./dataset1/valid', test_transform) valid_data = DataLoader(valid_set, 2*batch_size, shuffle=False, num_workers=0) train_set.class_to_idx len(valid_data) # 数据集准备 try: if iter(train_data).next()[0].shape[0] == batch_size and \ iter(valid_data).next()[0].shape[0] == 2*batch_size: print('Dataset is ready!') else: print('Not success, maybe the batch size is wrong') except: print('not success, image transform is wrong!')
模型构建并准备模型
# 构建模型 def get_model(): model = models.resnet50(pretrained=True) model.fc = nn.Linear(2048, 3) return model try: model = get_model() with torch.no_grad(): scorce = model(iter(train_data).next()[0]) print(scorce.shape[0], scorce.shape[1]) if scorce.shape[0] == batch_size and scorce.shape[1] == 3: print('Model is ready!') else: print('Model is failed!') except: print('model is wrong') if use_gpu: model = model.cuda()
构建模型优化器
# 构建loss函数和优化器 criterion = nn.CrossEntropyLoss() optimizer = torch.optim.Adam(model.parameters(), lr = 1e-4) # 训练的epoches数目 max_epoch = 20
模型训练和训练结果可视化
数据集和训练集准备好后进行模型训练和训练结果可视化，部分代码如下：
def train(model, train_data, valid_data, max_epoch, criterion, optimizer): freq_print = int(len(train_data) / 3) metric_log = dict() metric_log['train_loss'] = list() metric_log['train_acc'] = list() if valid_data is not None: metric_log['valid_loss'] = list() metric_log['valid_acc'] = list() for e in range(max_epoch): model.train() running_loss = 0 running_acc = 0 for i, data in enumerate(train_data, 1): img, label = data if use_gpu: img = img.cuda() label = label.cuda() # forward前向传播 out = model(img) # 计算误差 loss = criterion(out, label.long()) # 反向传播，更新参数 optimizer.zero_grad() loss.backward() optimizer.step() # 计算准确率 _, pred = out.max(1) num_correct = (pred == label.long()).sum().item() acc = num_correct/img.shape[0] running_loss += loss.item() running_acc +=acc if i % freq_print == 0: print('[{}]/[{}], train loss: {:.3f}, train acc: {:.3f}' \ .format(i, len(train_data), running_loss / i, running_acc / i)) metric_log['train_loss'].append(running_loss / len(train_data)) metric_log['train_acc'].append(running_acc / len(train_data)) if valid_data is not None: model.eval() running_loss = 0 running_acc = 0 for data in valid_data: img, label = data if use_gpu: img = img.cuda() label = label.cuda() # forward前向传播 out = model(img) # 计算误差 loss = criterion(out, label.long()) # 计算准确度 _, pred = out.max(1) num_correct = (pred==label.long()).sum().item() acc = num_correct/img.shape[0] running_loss += loss.item() running_acc += acc metric_log['valid_loss'].append(running_loss/len(valid_data)) metric_log['valid_acc'].append(running_acc/len(valid_data)) print_str = 'epoch: {}, train loss: {:.3f}, train acc: {:.3f}, \ valid loss: {:.3f}, valid accuracy: {:.3f}'.format( e+1, metric_log['train_loss'][-1], metric_log['train_acc'][-1], metric_log['valid_loss'][-1], metric_log['valid_acc'][-1]) else: print_str = 'epoch: {}, train loss: {:.3f}, train acc: {:.3f}'.format( e+1, metric_log['train_loss'][-1], metric_log['train_acc'][-1]) print(print_str) # 可视化 nrows = 1 ncols = 2 figsize= (10, 5) _, figs = plt.subplots(nrows, ncols, figsize=figsize) if valid_data is not None: figs[0].plot(metric_log['train_loss'], label='train loss') figs[0].plot(metric_log['valid_loss'], label='valid loss') figs[0].axes.set_xlabel('loss') figs[0].legend(loc='best') figs[1].plot(metric_log['train_acc'], label='train acc') figs[1].plot(metric_log['valid_acc'], label='valid acc') figs[1].axes.set_xlabel('acc') figs[1].legend(loc='best') else: figs[0].plot(metric_log['train_loss'], label='train loss') figs[0].axes.set_xlabel('loss') figs[0].legend(loc='best') figs[1].plot(metric_log['train_acc'], label='train acc') figs[1].axes.set_xlabel('acc') figs[1].legend(loc='best')
调参进行模型训练
# 用作调参 train(model, train_data, valid_data, max_epoch, criterion, optimizer)
保存模型
# 保存模型 torch.save(model.state_dict(), './model/save_model2.pth')
总结
今天的文章主要是讲图像识别模型如何构建。希望对大家有所帮助。
你安利到了吗？
