本文主要是介绍第97步 深度学习图像目标检测：RetinaNet建模，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
基于WIN10的64位系统演示
一、写在前面
本期开始，我们继续学习深度学习图像目标检测系列，RetinaNet模型。
二、RetinaNet简介
RetinaNet 是由 Facebook AI Research (FAIR) 的研究人员在 2017 年提出的一种目标检测模型。它是一种单阶段（one-stage）的目标检测方法，但通过引入一个名为 Focal Loss 的创新损失函数，RetinaNet 解决了单阶段检测器常面临的正负样本不平衡问题。以下是 RetinaNet 的主要特点：
（1）Focal Loss：
传统的交叉熵损失往往由于背景类（负样本）的数量远大于目标类（正样本）而导致训练不稳定。为了解决这一不平衡问题，RetinaNet 引入了 Focal Loss。Focal Loss 被设计为更重视那些难以分类的负样本，而减少对容易分类的背景类的关注。这有助于提高模型对目标的检测精度。
（2）特征金字塔网络 (FPN)：
RetinaNet 使用了特征金字塔网络 (FPN) 作为其骨干网络，这是一个为多尺度目标检测设计的卷积网络结构。FPN 可以从单张图像中提取多尺度的特征，使得模型能够有效地检测不同大小的物体。
（3）预定义锚框：
与其他一阶段检测器相似，RetinaNet 在其特征图上使用预定义的锚框来预测目标的位置和类别。
三、数据源
来源于公共数据，文件设置如下：
大概的任务就是：用一个框框标记出MTB的位置。
四、RetinaNet实战
直接上代码：
import os
import random
import torch
import torchvision
from torchvision.models.detection import retinanet_resnet50_fpn
from torchvision.transforms import functional as F
from PIL import Image
from torch.utils.data import DataLoader
import xml.etree.ElementTree as ET
import matplotlib.pyplot as plt
from torchvision import transforms
import albumentations as A
from albumentations.pytorch import ToTensorV2
import numpy as np# Function to parse XML annotations
def parse_xml(xml_path):tree = ET.parse(xml_path)root = tree.getroot()boxes = []for obj in root.findall("object"):bndbox = obj.find("bndbox")xmin = int(bndbox.find("xmin").text)ymin = int(bndbox.find("ymin").text)xmax = int(bndbox.find("xmax").text)ymax = int(bndbox.find("ymax").text)# Check if the bounding box is validif xmin < xmax and ymin < ymax:boxes.append((xmin, ymin, xmax, ymax))else:print(f"Warning: Ignored invalid box in {xml_path} - ({xmin}, {ymin}, {xmax}, {ymax})")return boxes# Function to split data into training and validation sets
def split_data(image_dir, split_ratio=0.8):all_images = [f for f in os.listdir(image_dir) if f.endswith(".jpg")]random.shuffle(all_images)split_idx = int(len(all_images) * split_ratio)train_images = all_images[:split_idx]val_images = all_images[split_idx:]return train_images, val_images# Dataset class for the Tuberculosis dataset
class TuberculosisDataset(torch.utils.data.Dataset):def __init__(self, image_dir, annotation_dir, image_list, transform=None):self.image_dir = image_dirself.annotation_dir = annotation_dirself.image_list = image_listself.transform = transformdef __len__(self):return len(self.image_list)def __getitem__(self, idx):image_path = os.path.join(self.image_dir, self.image_list[idx])image = Image.open(image_path).convert("RGB")xml_path = os.path.join(self.annotation_dir, self.image_list[idx].replace(".jpg", ".xml"))boxes = parse_xml(xml_path)# Check for empty bounding boxes and return Noneif len(boxes) == 0:return Noneboxes = torch.as_tensor(boxes, dtype=torch.float32)labels = torch.ones((len(boxes),), dtype=torch.int64)iscrowd = torch.zeros((len(boxes),), dtype=torch.int64)target = {}target["boxes"] = boxestarget["labels"] = labelstarget["image_id"] = torch.tensor([idx])target["iscrowd"] = iscrowd# Apply transformationsif self.transform:image = self.transform(image)return image, target# Define the transformations using torchvision
data_transform = torchvision.transforms.Compose([torchvision.transforms.ToTensor(), # Convert PIL image to tensortorchvision.transforms.Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225]) # Normalize the images
])# Adjusting the DataLoader collate function to handle None values
def collate_fn(batch):batch = list(filter(lambda x: x is not None, batch))return tuple(zip(*batch))def get_retinanet_model_for_finetuning(num_classes):# Load a RetinaNet model with a ResNet-50-FPN backbone without pre-trained weightsmodel = retinanet_resnet50_fpn(pretrained=False, num_classes=num_classes)return model# Function to save the model
def save_model(model, path="RetinaNet_mtb.pth", save_full_model=False):if save_full_model:torch.save(model, path)else:torch.save(model.state_dict(), path)print(f"Model saved to {path}")# Function to compute Intersection over Union
def compute_iou(boxA, boxB):xA = max(boxA[0], boxB[0])yA = max(boxA[1], boxB[1])xB = min(boxA[2], boxB[2])yB = min(boxA[3], boxB[3])interArea = max(0, xB - xA + 1) * max(0, yB - yA + 1)boxAArea = (boxA[2] - boxA[0] + 1) * (boxA[3] - boxA[1] + 1)boxBArea = (boxB[2] - boxB[0] + 1) * (boxB[3] - boxB[1] + 1)iou = interArea / float(boxAArea + boxBArea - interArea)return iou# Adjusting the DataLoader collate function to handle None values and entirely empty batches
def collate_fn(batch):batch = list(filter(lambda x: x is not None, batch))if len(batch) == 0:# Return placeholder batch if entirely emptyreturn [torch.zeros(1, 3, 224, 224)], [{}]return tuple(zip(*batch))#Training function with modifications for collecting IoU and loss
def train_model(model, train_loader, optimizer, device, num_epochs=10):model.train()model.to(device)loss_values = []iou_values = []for epoch in range(num_epochs):epoch_loss = 0.0total_ious = 0num_boxes = 0for images, targets in train_loader:# Skip batches with placeholder dataif len(targets) == 1 and not targets[0]:continue# Skip batches with empty targetsif any(len(target["boxes"]) == 0 for target in targets):continueimages = [image.to(device) for image in images]targets = [{k: v.to(device) for k, v in t.items()} for t in targets]loss_dict = model(images, targets)losses = sum(loss for loss in loss_dict.values())optimizer.zero_grad()losses.backward()optimizer.step()epoch_loss += losses.item()# Compute IoU for evaluationwith torch.no_grad():model.eval()predictions = model(images)for i, prediction in enumerate(predictions):pred_boxes = prediction["boxes"].cpu().numpy()true_boxes = targets[i]["boxes"].cpu().numpy()for pred_box in pred_boxes:for true_box in true_boxes:iou = compute_iou(pred_box, true_box)total_ious += iounum_boxes += 1model.train()avg_loss = epoch_loss / len(train_loader)avg_iou = total_ious / num_boxes if num_boxes != 0 else 0loss_values.append(avg_loss)iou_values.append(avg_iou)print(f"Epoch {epoch+1}/{num_epochs} Loss: {avg_loss} Avg IoU: {avg_iou}")# Plotting loss and IoU valuesplt.figure(figsize=(12, 5))plt.subplot(1, 2, 1)plt.plot(loss_values, label="Training Loss")plt.title("Training Loss across Epochs")plt.xlabel("Epochs")plt.ylabel("Loss")plt.subplot(1, 2, 2)plt.plot(iou_values, label="IoU")plt.title("IoU across Epochs")plt.xlabel("Epochs")plt.ylabel("IoU")plt.show()# Save model after trainingsave_model(model)# Validation function
def validate_model(model, val_loader, device):model.eval()model.to(device)with torch.no_grad():for images, targets in val_loader:images = [image.to(device) for image in images]targets = [{k: v.to(device) for k, v in t.items()} for t in targets]model(images)# Paths to your data
image_dir = "tuberculosis-phonecamera"
annotation_dir = "tuberculosis-phonecamera"# Split data
train_images, val_images = split_data(image_dir)# Create datasets and dataloaders
train_dataset = TuberculosisDataset(image_dir, annotation_dir, train_images, transform=data_transform)
val_dataset = TuberculosisDataset(image_dir, annotation_dir, val_images, transform=data_transform)# Updated DataLoader with new collate function
train_loader = DataLoader(train_dataset, batch_size=4, shuffle=True, collate_fn=collate_fn)
val_loader = DataLoader(val_dataset, batch_size=4, shuffle=False, collate_fn=collate_fn)# Model and optimizer
model = get_retinanet_model_for_finetuning(2)
optimizer = torch.optim.Adam(model.parameters(), lr=0.001)# Train and validate
train_model(model, train_loader, optimizer, device="cuda", num_epochs=10)
validate_model(model, val_loader, device="cuda")#######################################Print Metrics######################################
def calculate_metrics(predictions, ground_truths, iou_threshold=0.5):TP = 0 # True PositivesFP = 0 # False PositivesFN = 0 # False Negativestotal_iou = 0 # to calculate mean IoUfor pred, gt in zip(predictions, ground_truths):pred_boxes = pred["boxes"].cpu().numpy()gt_boxes = gt["boxes"].cpu().numpy()# Match predicted boxes to ground truth boxesfor pred_box in pred_boxes:max_iou = 0matched = Falsefor gt_box in gt_boxes:iou = compute_iou(pred_box, gt_box)if iou > max_iou:max_iou = iouif iou > iou_threshold:matched = Truetotal_iou += max_iouif matched:TP += 1else:FP += 1FN += len(gt_boxes) - TPprecision = TP / (TP + FP) if (TP + FP) != 0 else 0recall = TP / (TP + FN) if (TP + FN) != 0 else 0f1_score = (2 * precision * recall) / (precision + recall) if (precision + recall) != 0 else 0mean_iou = total_iou / (TP + FP) if (TP + FP) != 0 else 0return precision, recall, f1_score, mean_ioudef evaluate_model(model, dataloader, device):model.eval()model.to(device)all_predictions = []all_ground_truths = []with torch.no_grad():for images, targets in dataloader:images = [image.to(device) for image in images]predictions = model(images)all_predictions.extend(predictions)all_ground_truths.extend(targets)precision, recall, f1_score, mean_iou = calculate_metrics(all_predictions, all_ground_truths)return precision, recall, f1_score, mean_ioutrain_precision, train_recall, train_f1, train_iou = evaluate_model(model, train_loader, "cuda")
val_precision, val_recall, val_f1, val_iou = evaluate_model(model, val_loader, "cuda")print("Training Set Metrics:")
print(f"Precision: {train_precision:.4f}, Recall: {train_recall:.4f}, F1 Score: {train_f1:.4f}, Mean IoU: {train_iou:.4f}")print("\nValidation Set Metrics:")
print(f"Precision: {val_precision:.4f}, Recall: {val_recall:.4f}, F1 Score: {val_f1:.4f}, Mean IoU: {val_iou:.4f}")#sheet
header = "| Metric | Training Set | Validation Set |"
divider = "+----------+--------------+----------------+"train_metrics = f"| Precision | {train_precision:.4f} | {val_precision:.4f} |"
recall_metrics = f"| Recall | {train_recall:.4f} | {val_recall:.4f} |"
f1_metrics = f"| F1 Score | {train_f1:.4f} | {val_f1:.4f} |"
iou_metrics = f"| Mean IoU | {train_iou:.4f} | {val_iou:.4f} |"print(header)
print(divider)
print(train_metrics)
print(recall_metrics)
print(f1_metrics)
print(iou_metrics)
print(divider)#######################################Train Set######################################
import numpy as np
import matplotlib.pyplot as pltdef plot_predictions_on_image(model, dataset, device, title):# Select a random image from the datasetidx = np.random.randint(50, len(dataset))image, target = dataset[idx]img_tensor = image.clone().detach().to(device).unsqueeze(0)# Use the model to make predictionsmodel.eval()with torch.no_grad():prediction = model(img_tensor)# Inverse normalization for visualizationinv_normalize = transforms.Normalize(mean=[-0.485/0.229, -0.456/0.224, -0.406/0.225],std=[1/0.229, 1/0.224, 1/0.225])image = inv_normalize(image)image = torch.clamp(image, 0, 1)image = F.to_pil_image(image)# Plot the image with ground truth boxesplt.figure(figsize=(10, 6))plt.title(title + " with Ground Truth Boxes")plt.imshow(image)ax = plt.gca()# Draw the ground truth boxes in bluefor box in target["boxes"]:rect = plt.Rectangle((box[0], box[1]), box[2]-box[0], box[3]-box[1],fill=False, color='blue', linewidth=2)ax.add_patch(rect)plt.show()# Plot the image with predicted boxesplt.figure(figsize=(10, 6))plt.title(title + " with Predicted Boxes")plt.imshow(image)ax = plt.gca()# Draw the predicted boxes in redfor box in prediction[0]["boxes"].cpu():rect = plt.Rectangle((box[0], box[1]), box[2]-box[0], box[3]-box[1],fill=False, color='red', linewidth=2)ax.add_patch(rect)plt.show()# Call the function for a random image from the train dataset
plot_predictions_on_image(model, train_dataset, "cuda", "Selected from Training Set")#######################################Val Set####################################### Call the function for a random image from the validation dataset
plot_predictions_on_image(model, val_dataset, "cuda", "Selected from Validation Set")这回也是需要从头训练的，就不跑了。
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