feat: 用 Grad-CAM 从分类模型生成弱监督框标签
分类模型只学过"是什么缺陷"，Grad-CAM 把分类分数对卷积特征的梯度当作通道重要性， 加权求和得到空间热力图，阈值化 + 连通域外接矩形即得到框标签，输出 YOLO 格式， 可直接接入既有的检测训练链路。 - engine/gradcam.py：整批一次 backward 的 Grad-CAM（各样本只回传自己那一类的分数）、 numpy 实现的 4-邻接连通域标记（不为这一处引入 scipy/opencv）、CAM 转归一化框 - scripts/gradcam_boxes.py：遍历数据集生成标签，并输出「原图 | 热力图 | 叠加+框」 三联图供人工核对；框的类别取自图片所在目录而非模型预测 两处按实图定下的默认值： - --stage 默认 6（layer3, 8×8）。layer4 只有 4×4 太粗，layer2 响应太散导致 40% 出不了框 - --peak-ratio 0.75：次要连通域峰值需达全局最大值的 75%，否则会在无缺陷的角落刷假框； 实测把两框比例从 53% 降到 20% 全量 11,212 张已生成：61.8% 出 1 框、35.2% 出 2 框、3.0% 无框，每类留 25 张可视化。 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Shaun Zhou
co-authored by
Claude Opus 5
Claude Opus 5
parent
33fdf396ee
commit
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#!/usr/bin/env python
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"""用训练好的分类模型 + Grad-CAM 为每张图生成框标签。
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uv run python scripts/gradcam_boxes.py --checkpoint runs/classify/best.pth
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分类模型只学过"这是什么缺陷"。Grad-CAM 把分类分数对卷积特征的梯度当作通道重要性，
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加权求和得到空间热力图——这是分类模型隐含的定位线索。阈值化 + 取连通域外接矩形，
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就得到弱监督的框标签。
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产出：
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```
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runs/gradcam_boxes/
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├── labels/<类别>/<图名>.txt # YOLO 格式：class_id cx cy w h（归一化）
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├── viz/<类别>/<图名>.png # 原图 | 热力图 | 叠加+框，供人工核对匹配程度
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├── data.yaml # 类别表，可直接喂给检测训练
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└── summary.json
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```
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**框的类别取自图片所在目录**（人工归类的结果），不是模型预测——即使模型分错，
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我们要的也是该图真实类别的热力区域。
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分辨率是主要限制：resnet18 在 128×128 输入下 layer4 只有 4×4、layer3 有 8×8。
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`--stage` 可选层（4~7 对应 layer1~4），层越浅越精细但类别判别性越弱。
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"""
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from __future__ import annotations
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import argparse
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import json
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import sys
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from collections import Counter
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from pathlib import Path
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sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
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import numpy as np # noqa: E402
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import torch # noqa: E402
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from PIL import Image # noqa: E402
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from torch.utils.data import DataLoader # noqa: E402
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from datasets import FolderClassificationDataset, classification_collate # noqa: E402
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from datasets.yolo import write_data_yaml # noqa: E402
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from engine import load_checkpoint # noqa: E402
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from engine.gradcam import cam_to_boxes, grad_cam, to_yolo_line # noqa: E402
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from models import build_model # noqa: E402
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from utils import load_config, setup_logging # noqa: E402
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from utils.device import DeviceNotAvailableError, describe_device, resolve_device # noqa: E402
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logger = None
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def save_visualization(path: Path, image_path: Path, cam: np.ndarray, boxes, title: str) -> None:
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"""三联图：原图 | 热力图 | 叠加+框。人工一眼就能看出热力区域与框合不合。"""
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import matplotlib
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matplotlib.use("Agg")
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import matplotlib.pyplot as plt
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from matplotlib.patches import Rectangle
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with Image.open(image_path) as raw:
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image = np.asarray(raw.convert("RGB"))
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height, width = image.shape[:2]
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heat = np.asarray(
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Image.fromarray((cam * 255).astype(np.uint8)).resize((width, height), Image.BILINEAR)
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) / 255.0
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fig, axes = plt.subplots(1, 3, figsize=(11, 4))
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axes[0].imshow(image)
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axes[0].set_title("original")
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axes[1].imshow(heat, cmap="jet", vmin=0, vmax=1)
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axes[1].set_title(f"grad-cam {cam.shape[0]}x{cam.shape[1]}")
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axes[2].imshow(image)
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axes[2].imshow(heat, cmap="jet", alpha=0.45, vmin=0, vmax=1)
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for x1, y1, x2, y2 in boxes:
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axes[2].add_patch(
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Rectangle(
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(x1 * width, y1 * height), (x2 - x1) * width, (y2 - y1) * height,
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fill=False, edgecolor="lime", linewidth=2,
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)
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)
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axes[2].set_title(f"overlay + {len(boxes)} box")
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for ax in axes:
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ax.axis("off")
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fig.suptitle(title, fontsize=10)
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fig.tight_layout()
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path.parent.mkdir(parents=True, exist_ok=True)
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fig.savefig(path, dpi=110)
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plt.close(fig)
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def main() -> int:
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global logger
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parser = argparse.ArgumentParser(
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description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter
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)
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parser.add_argument("--checkpoint", default="runs/classify/best.pth", help="分类模型权重")
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parser.add_argument("--config", default="configs/classify/film.yaml", help="训练时的配置")
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parser.add_argument("--out", default="runs/gradcam_boxes", help="输出目录")
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parser.add_argument("--set", nargs="*", default=[], metavar="KEY=VALUE")
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parser.add_argument("--device", default=None)
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parser.add_argument(
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"--stage", type=int, default=6,
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help="取骨架 features 的第几层做 CAM（4~7 = layer1~4）；默认 6 即 layer3",
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)
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parser.add_argument("--threshold", type=float, default=0.4, help="热力图阈值（相对最大值）")
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parser.add_argument("--padding", type=float, default=0.1, help="框四周外扩比例")
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parser.add_argument("--max-boxes", type=int, default=2, help="每张图最多几个框")
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parser.add_argument(
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"--min-area-ratio", type=float, default=0.02, help="连通域面积下限（占整图比例）"
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)
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parser.add_argument(
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"--peak-ratio", type=float, default=0.75,
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help="次要连通域的峰值至少要达到全局最大值的这个比例才保留，用于滤掉弱响应假框",
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)
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parser.add_argument(
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"--viz-per-class", type=int, default=20, help="每个类别存多少张可视化，0 = 不存"
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)
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parser.add_argument("--viz-all", action="store_true", help="每张图都存可视化（很慢很占盘）")
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parser.add_argument("--limit", type=int, default=0, help="只处理前 N 张，用于快速试参数")
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args = parser.parse_args()
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out_dir = Path(args.out)
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out_dir.mkdir(parents=True, exist_ok=True)
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logger = setup_logging(out_dir / "gradcam.log")
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cfg = load_config(args.config, args.set)
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try:
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device = resolve_device(args.device or cfg.get("device", "auto"))
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except DeviceNotAvailableError as exc:
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logger.error("%s", exc)
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return 1
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data_cfg = cfg["data"]
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dataset = FolderClassificationDataset(
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root=data_cfg["root"],
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split="all", # 为每个样本都生成，不分训练/验证
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classes=data_cfg.get("classes"),
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transforms=data_cfg["val_transforms"],
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exclude=data_cfg.get("exclude") or [],
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)
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if args.limit:
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dataset.samples = dataset.samples[: args.limit]
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classes = dataset.classes
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model_cfg = dict(cfg["model"])
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model_cfg.setdefault("num_classes", len(classes))
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model_cfg["init_from"] = None # 权重从 checkpoint 来，不要再读自监督骨架
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model = build_model(model_cfg)
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load_checkpoint(args.checkpoint, model, map_location=device)
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model.to(device).eval()
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for param in model.parameters(): # Grad-CAM 需要梯度，但不更新权重
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param.requires_grad_(True)
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logger.info("设备: %s | 权重: %s", describe_device(device), args.checkpoint)
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logger.info("数据集 %s：%d 张，%d 类", data_cfg["root"], len(dataset), len(classes))
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logger.info(
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"CAM 目标层 features[%d] | 阈值 %.2f | 外扩 %.2f | 每图最多 %d 框",
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args.stage, args.threshold, args.padding, args.max_boxes,
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)
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loader = DataLoader(
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dataset,
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batch_size=int(data_cfg.get("loader", {}).get("batch_size", 64)),
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shuffle=False,
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num_workers=int(data_cfg.get("loader", {}).get("num_workers", 4)),
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collate_fn=classification_collate,
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)
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labels_dir = out_dir / "labels"
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viz_dir = out_dir / "viz"
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viz_done: Counter[str] = Counter()
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box_counts: Counter[int] = Counter()
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per_class_boxes: Counter[str] = Counter()
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correct = 0
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cam_shape = None
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for step, batch in enumerate(loader):
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images = batch["images"].to(device)
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targets = batch["labels"].to(device)
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cams = grad_cam(model.backbone, model.head, images, targets, stage=args.stage)
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with torch.no_grad():
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correct += int((model(images).argmax(1) == targets).sum())
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cam_shape = tuple(cams.shape[-2:])
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for cam, target, meta in zip(cams.cpu().numpy(), targets.cpu().tolist(), batch["meta"],
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strict=True):
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name = classes[target]
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boxes = cam_to_boxes(
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cam,
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threshold=args.threshold,
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min_area_ratio=args.min_area_ratio,
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max_boxes=args.max_boxes,
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padding=args.padding,
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peak_ratio=args.peak_ratio,
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)
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box_counts[len(boxes)] += 1
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per_class_boxes[name] += len(boxes)
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source = Path(meta["path"])
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label_path = labels_dir / name / f"{source.stem}.txt"
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label_path.parent.mkdir(parents=True, exist_ok=True)
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label_path.write_text(
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"\n".join(to_yolo_line(box, target) for box in boxes) + ("\n" if boxes else ""),
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encoding="utf-8",
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)
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if args.viz_all or viz_done[name] < args.viz_per_class:
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viz_done[name] += 1
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save_visualization(
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viz_dir / name / f"{source.stem}.png", source, cam, boxes,
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f"{name} | {len(boxes)} box | thr={args.threshold}",
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)
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if step % 20 == 0:
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logger.info("处理 [%d/%d]", step, len(loader))
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total = sum(box_counts.values())
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write_data_yaml(out_dir / "data.yaml", classes, root=out_dir)
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summary = {
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"checkpoint": args.checkpoint,
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"dataset": str(data_cfg["root"]),
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"num_images": total,
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"cam_shape": list(cam_shape) if cam_shape else None,
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"stage": args.stage,
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"threshold": args.threshold,
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"padding": args.padding,
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"max_boxes": args.max_boxes,
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"min_area_ratio": args.min_area_ratio,
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"peak_ratio": args.peak_ratio,
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"classification_accuracy_on_all": correct / total if total else 0.0,
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"boxes_per_image": {str(k): v for k, v in sorted(box_counts.items())},
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"boxes_per_class": dict(sorted(per_class_boxes.items())),
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}
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(out_dir / "summary.json").write_text(
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json.dumps(summary, ensure_ascii=False, indent=2), encoding="utf-8"
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)
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logger.info("CAM 分辨率 %s | 全量分类准确率 %.4f", cam_shape, summary["classification_accuracy_on_all"])
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for count, number in sorted(box_counts.items()):
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logger.info(" 生成 %d 个框的图片: %d 张 (%.1f%%)", count, number, 100 * number / total)
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logger.info("标签写入 %s，可视化 %d 张写入 %s", labels_dir, sum(viz_done.values()), viz_dir)
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return 0
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if __name__ == "__main__":
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raise SystemExit(main())
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