pytorch 实现Grad-CAM:Visual Explanations from Deep Networks via Gradient-based Localization 和
Grad-CAM++: Improved Visual Explanations for Deep Convolutional Networks
- 依赖
- 使用方法
- 样例分析
3.1 单个对象
3.3 多个对象 - 总结
- 目标检测-faster-r-cnn
5.1 detectron2安装
5.2 测试
5.3 Grad-CAM结果
5.4 总结 - 目标检测-retinanet
6.1 detectron2安装
6.2 测试
6.3 Grad-CAM结果
6.4 总结 - 目标检测-fcos
7.1 AdelaiDet安装
7.2 测试
7.3 Grad-CAM结果
7.4 总结
Grad-CAM整体架构
Grad-CAM++与Grad-CAM的异同
python 3.6.x
pytoch 1.0.1+
torchvision 0.2.2
opencv-python
matplotlib
scikit-image
numpypython main.py --image-path examples/pic1.jpg \
--network densenet121 \
--weight-path /opt/pretrained_model/densenet121-a639ec97.pth参数说明：
-
image-path：需要可视化的图像路径(可选,默认
./examples/pic1.jpg) -
network: 网络名称(可选,默认
resnet50) -
weight-path: 网络对应的与训练参数权重路径(可选,默认从pytorch官网下载对应的预训练权重)
-
layer-name: Grad-CAM使用的层名(可选,默认最后一个卷积层)
-
class-id：Grad-CAM和Guided Back Propagation反向传播使用的类别id（可选,默认网络预测的类别)
-
output-dir：可视化结果图像保存目录(可选，默认
results目录)
原始图像
效果
| network | HeatMap | Grad-CAM | HeatMap++ | Grad-CAM++ | Guided backpropagation | Guided Grad-CAM |
|---|---|---|---|---|---|---|
| vgg16 |  |
 |
 |
 |
 |
 |
| vgg19 |  |
 |
 |
 |
 |
 |
| resnet50 |  |
 |
 |
 |
 |
 |
| resnet101 |  |
 |
 |
|
 |
 |
| densenet121 |  |
 |
 |
 |
 |
 |
| inception_v3 |  |
 |
 |
 |
 |
 |
| mobilenet_v2 |  |
 |
 |
 |
 |
 |
| shufflenet_v2 |  |
 |
 |
 |
 |
 |
对应多个图像Grad-CAM++比Grad-CAM覆盖要更全面一些，这也是Grad-CAM++最主要的优势
原始图像
效果
| network | HeatMap | Grad-CAM | HeatMap++ | Grad-CAM++ | Guided backpropagation | Guided Grad-CAM |
|---|---|---|---|---|---|---|
| vgg16 |  |
 |
 |
 |
 |
 |
| vgg19 |  |
 |
 |
 |
 |
 |
| resnet50 |  |
 |
 |
 |
 |
 |
| resnet101 |  |
 |
 |
|
 |
 |
| densenet121 |  |
 |
 |
 |
 |
 |
| inception_v3 |  |
 |
 |
 |
 |
 |
| mobilenet_v2 |  |
 |
 |
 |
 |
 |
| shufflenet_v2 |  |
 |
 |
 |
 |
 |
- vgg模型的Grad-CAM并没有覆盖整个对象,相对来说resnet和denset覆盖更全,特别是densenet;从侧面说明就模型的泛化和鲁棒性而言densenet>resnet>vgg
- Grad-CAM++相对于Grad-CAM也是覆盖对象更全面，特别是对于同一个类别有多个实例的情况下,Grad-CAM可能只覆盖部分对象，Grad-CAM++基本覆盖所有对象;但是这仅仅对于vgg而言,想densenet直接使用Grad-CAM也基本能够覆盖所有对象
- MobileNet V2的Grad-CAM覆盖也很全面
- Inception V3和MobileNet V2的Guided backpropagation图轮廓很模糊，但是ShuffleNet V2的轮廓则比较清晰
有位网友SHAOSIHAN问道怎样在目标检测中使用Grad-CAM;在Grad-CAM和Grad-CAM++论文中都没有提及对目标检测生成CAM图。我想主要有两个原因：
a) 目标检测不同于分类，分类网络只有一个分类损失，而且所有网络都是一样的(几个类别最后一层就是几个神经元)，最后的预测输出都是单一的类别得分分布。目标检测则不同，输出都不是单一的，而且不同的网络如Faster R-CNN, CornerNet,CenterNet,FCOS，它们的建模方式不一样，输出的含义都不相同。所以不会有统一的生成Grad-CAM图的方法。
b) 分类属于弱监督，通过CAM可以了解网络预测时主要关注的空间位置，也就是"看哪里"，对分析问题有实际的价值；而目标检测，本身是强监督，预测边框就直接指示了“看哪里”。
这里以detetron2中的faster-rcnn网络为例，生成Grad-CAM图。主要思路是直接获取预测分值最高的边框;将该边框的预测分值反向传播梯度到，该边框对应的proposal 边框的feature map上，生成此feature map的CAM图。
a) 下载
git clone https://github.com/facebookresearch/detectron2.gitb) 修改detectron2/modeling/roi_heads/fast_rcnn.py文件中的fast_rcnn_inference_single_image函数，主要是增加索引号，记录分值高的预测边框是由第几个proposal边框生成的；修改后的fast_rcnn_inference_single_image函数如下：
def fast_rcnn_inference_single_image(
boxes, scores, image_shape, score_thresh, nms_thresh, topk_per_image
):
"""
Single-image inference. Return bounding-box detection results by thresholding
on scores and applying non-maximum suppression (NMS).
Args:
Same as `fast_rcnn_inference`, but with boxes, scores, and image shapes
per image.
Returns:
Same as `fast_rcnn_inference`, but for only one image.
"""
valid_mask = torch.isfinite(boxes).all(dim=1) & torch.isfinite(scores).all(dim=1)
indices = torch.arange(start=0, end=scores.shape[0], dtype=int)
indices = indices.expand((scores.shape[1], scores.shape[0])).T
if not valid_mask.all():
boxes = boxes[valid_mask]
scores = scores[valid_mask]
indices = indices[valid_mask]
scores = scores[:, :-1]
indices = indices[:, :-1]
num_bbox_reg_classes = boxes.shape[1] // 4
# Convert to Boxes to use the `clip` function ...
boxes = Boxes(boxes.reshape(-1, 4))
boxes.clip(image_shape)
boxes = boxes.tensor.view(-1, num_bbox_reg_classes, 4) # R x C x 4
# Filter results based on detection scores
filter_mask = scores > score_thresh # R x K
# R' x 2. First column contains indices of the R predictions;
# Second column contains indices of classes.
filter_inds = filter_mask.nonzero()
if num_bbox_reg_classes == 1:
boxes = boxes[filter_inds[:, 0], 0]
else:
boxes = boxes[filter_mask]
scores = scores[filter_mask]
indices = indices[filter_mask]
# Apply per-class NMS
keep = batched_nms(boxes, scores, filter_inds[:, 1], nms_thresh)
if topk_per_image >= 0:
keep = keep[:topk_per_image]
boxes, scores, filter_inds = boxes[keep], scores[keep], filter_inds[keep]
indices = indices[keep]
result = Instances(image_shape)
result.pred_boxes = Boxes(boxes)
result.scores = scores
result.pred_classes = filter_inds[:, 1]
result.indices = indices
return result, filter_inds[:, 0]c) 安装;如遇到问题，请参考detectron2；不同操作系统安装有差异
cd detectron2
pip install -e .a) 预训练模型下载
wget https://dl.fbaipublicfiles.com/detectron2/PascalVOC-Detection/faster_rcnn_R_50_C4/142202221/model_final_b1acc2.pklb) 测试Grad-CAM图像生成
在本工程目录下执行如下命令
export KMP_DUPLICATE_LIB_OK=TRUE
python detection/demo.py --config-file detection/faster_rcnn_R_50_C4.yaml \
--input ./examples/pic1.jpg \
--opts MODEL.WEIGHTS /Users/yizuotian/pretrained_model/model_final_b1acc2.pkl MODEL.DEVICE cpu| 原始图像 | 检测边框 | Grad-CAM HeatMap | Grad-CAM++ HeatMap | 边框预测类别 |
|---|---|---|---|---|
 |
 |
 |
 |
Dog |
 |
 |
 |
 |
Aeroplane |
 |
 |
 |
 |
Person |
 |
 |
 |
 |
Horse |
对于目标检测Grad-CAM++的效果并没有比Grad-CAM效果好，推测目标检测中预测边框已经是单个对象了,Grad-CAM++在多个对象的情况下优于Grad-CAM
在目标检测网络faster r-cnn的Grad-CAM完成后，有两位网友abhigoku10 、wangzyon问道怎样在retinanet中实现Grad-CAM。retinanet与faster r-cnn网络结构不同，CAM的生成也有一些差异；以下是详细的过程：
a) 下载
git clone https://github.com/facebookresearch/detectron2.gitb) 修改detectron2/modeling/meta_arch/retinanet.py 文件中的inference_single_image函数，主要是增加feature level 索引，记录分值高的预测边框是由第几层feature map生成的；修改后的inference_single_image函数如下：
def inference_single_image(self, box_cls, box_delta, anchors, image_size):
"""
Single-image inference. Return bounding-box detection results by thresholding
on scores and applying non-maximum suppression (NMS).
Arguments:
box_cls (list[Tensor]): list of #feature levels. Each entry contains
tensor of size (H x W x A, K)
box_delta (list[Tensor]): Same shape as 'box_cls' except that K becomes 4.
anchors (list[Boxes]): list of #feature levels. Each entry contains
a Boxes object, which contains all the anchors for that
image in that feature level.
image_size (tuple(H, W)): a tuple of the image height and width.
Returns:
Same as `inference`, but for only one image.
"""
boxes_all = []
scores_all = []
class_idxs_all = []
feature_level_all = []
# Iterate over every feature level
for i, (box_cls_i, box_reg_i, anchors_i) in enumerate(zip(box_cls, box_delta, anchors)):
# (HxWxAxK,)
box_cls_i = box_cls_i.flatten().sigmoid_()
# Keep top k top scoring indices only.
num_topk = min(self.topk_candidates, box_reg_i.size(0))
# torch.sort is actually faster than .topk (at least on GPUs)
predicted_prob, topk_idxs = box_cls_i.sort(descending=True)
predicted_prob = predicted_prob[:num_topk]
topk_idxs = topk_idxs[:num_topk]
# filter out the proposals with low confidence score
keep_idxs = predicted_prob > self.score_threshold
predicted_prob = predicted_prob[keep_idxs]
topk_idxs = topk_idxs[keep_idxs]
anchor_idxs = topk_idxs // self.num_classes
classes_idxs = topk_idxs % self.num_classes
box_reg_i = box_reg_i[anchor_idxs]
anchors_i = anchors_i[anchor_idxs]
# predict boxes
predicted_boxes = self.box2box_transform.apply_deltas(box_reg_i, anchors_i.tensor)
boxes_all.append(predicted_boxes)
scores_all.append(predicted_prob)
class_idxs_all.append(classes_idxs)
feature_level_all.append(torch.ones_like(classes_idxs) * i)
boxes_all, scores_all, class_idxs_all, feature_level_all = [
cat(x) for x in [boxes_all, scores_all, class_idxs_all, feature_level_all]
]
keep = batched_nms(boxes_all, scores_all, class_idxs_all, self.nms_threshold)
keep = keep[: self.max_detections_per_image]
result = Instances(image_size)
result.pred_boxes = Boxes(boxes_all[keep])
result.scores = scores_all[keep]
result.pred_classes = class_idxs_all[keep]
result.feature_levels = feature_level_all[keep]
return resultc) 修改detectron2/modeling/meta_arch/retinanet.py 文件增加predict函数，具体如下：
def predict(self, batched_inputs):
"""
Args:
batched_inputs: a list, batched outputs of :class:`DatasetMapper` .
Each item in the list contains the inputs for one image.
For now, each item in the list is a dict that contains:
* image: Tensor, image in (C, H, W) format.
* instances: Instances
Other information that's included in the original dicts, such as:
* "height", "width" (int): the output resolution of the model, used in inference.
See :meth:`postprocess` for details.
Returns:
dict[str: Tensor]:
mapping from a named loss to a tensor storing the loss. Used during training only.
"""
images = self.preprocess_image(batched_inputs)
features = self.backbone(images.tensor)
features = [features[f] for f in self.in_features]
box_cls, box_delta = self.head(features)
anchors = self.anchor_generator(features)
results = self.inference(box_cls, box_delta, anchors, images.image_sizes)
processed_results = []
for results_per_image, input_per_image, image_size in zip(
results, batched_inputs, images.image_sizes
):
height = input_per_image.get("height", image_size[0])
width = input_per_image.get("width", image_size[1])
r = detector_postprocess(results_per_image, height, width)
processed_results.append({"instances": r})
return processed_resultsd) 安装;如遇到问题，请参考detectron2；不同操作系统安装有差异
cd detectron2
pip install -e .a) 预训练模型下载
wget https://dl.fbaipublicfiles.com/detectron2/COCO-Detection/retinanet_R_50_FPN_3x/137849486/model_final_4cafe0.pklb) 测试Grad-CAM图像生成
在本工程目录下执行如下命令:
export KMP_DUPLICATE_LIB_OK=TRUE
python detection/demo_retinanet.py --config-file detection/retinanet_R_50_FPN_3x.yaml \
--input ./examples/pic1.jpg \
--layer-name head.cls_subnet.0 \
--opts MODEL.WEIGHTS /Users/yizuotian/pretrained_model/model_final_4cafe0.pkl MODEL.DEVICE cpu| 图像1 | 图像2 | 图像3 | 图像4 | |
|---|---|---|---|---|
| 原图 | |
|
|
|
| 预测边框 |  |
 |
 |
 |
| GradCAM-cls_subnet.0 |  |
 |
 |
 |
| GradCAM-cls_subnet.1 |  |
 |
 |
 |
| GradCAM-cls_subnet.2 |  |
 |
 |
 |
| GradCAM-cls_subnet.3 |  |
 |
 |
 |
| GradCAM-cls_subnet.4 |  |
 |
 |
 |
| GradCAM-cls_subnet.5 |  |
 |
 |
 |
| GradCAM-cls_subnet.6 |  |
 |
 |
 |
| GradCAM-cls_subnet.7 |  |
 |
 |
 |
| GradCAM++-cls_subnet.0 |  |
 |
 |
 |
| GradCAM++-cls_subnet.1 |  |
 |
 |
 |
| GradCAM++-cls_subnet.2 |  |
 |
 |
 |
| GradCAM++-cls_subnet.3 |  |
 |
 |
 |
| GradCAM++-cls_subnet.4 |  |
 |
 |
 |
| GradCAM++-cls_subnet.5 |  |
 |
 |
 |
| GradCAM++-cls_subnet.6 |  |
 |
 |
 |
| GradCAM++-cls_subnet.7 |  |
 |
 |
 |
注：以上分别对head.cls_subnet.0~head.cls_subnet.7共8个层生成Grad-CAM图，这8层分别对应retinanet分类子网络的4层卷积feature map及ReLu激活后的feature map
a) retinanet的Grad-CAM图效果都不算好，相对来说中间层head.cls_subnet.2~head.cls_subnet.4相对好一点
b) 个人认为retinanet效果不要的原因是，retinanet最后的分类是卷积层，卷积核实3*3，也就是说反向传播到最后一个卷积层的feature map上，只有3*3个单元有梯度。而分类网络或者faster r-cnn分类都是全连接层，感受全局信息，最后一个卷积层的feature map上所有单元都有梯度。
c) 反向传播到浅层的feature map上，有梯度的单元会逐渐增加，但是就像Grad-CAM论文中说的，越浅层的feature map语义信息越弱，所以可以看到head.cls_subnet.0的CAM图效果很差。
在目标检测网络faster r-cnn和retinanet的Grad-CAM完成后，有位网友linsy-ai 问道怎样在fcos中实现Grad-CAM。fcos与retinanet基本类似，因为它们整体网络结构类似；这里使用AdelaiDet 工程中的fcos网络，以下是详细的过程：
a) 下载
git clone https://github.com/aim-uofa/AdelaiDet.gitb) 安装
cd AdelaiDet
python setup.py build develop注意：1. AdelaiDet安装依赖detectron2,需要首先安装$\color{red}{detectron2}$
2. fcos的不支持CPU,只支持GPU,请确保在$\color{red}{GPU环境}$下安装和测试
a) 预训练模型下载
wget https://cloudstor.aarnet.edu.au/plus/s/glqFc13cCoEyHYy/download -O fcos_R_50_1x.pthb) 测试Grad-CAM图像生成
在本工程目录下执行如下命令:
export CUDA_DEVICE_ORDER="PCI_BUS_ID"
export CUDA_VISIBLE_DEVICES="0"
python AdelaiDet/demo_fcos.py --config-file AdelaiDet/R_50_1x.yaml \
--input ./examples/pic1.jpg \
--layer-name proposal_generator.fcos_head.cls_tower.8 \
--opts MODEL.WEIGHTS /path/to/fcos_R_50_1x.pth MODEL.DEVICE cuda| 图像1 | 图像2 | 图像3 | 图像4 | |
|---|---|---|---|---|
| 原图 | |
|
|
|
| 预测边框 |  |
 |
 |
 |
| GradCAM-cls_tower.0 |  |
 |
 |
 |
| GradCAM-cls_tower.1 |  |
 |
 |
 |
| GradCAM-cls_tower.2 |  |
 |
 |
 |
| GradCAM-cls_tower.3 |  |
 |
 |
 |
| GradCAM-cls_tower.4 |  |
 |
 |
 |
| GradCAM-cls_tower.5 |  |
 |
 |
 |
| GradCAM-cls_tower.6 |  |
 |
 |
 |
| GradCAM-cls_tower.7 |  |
 |
 |
 |
| GradCAM-cls_tower.8 |  |
 |
 |
 |
| GradCAM-cls_tower.9 |  |
 |
 |
 |
| GradCAM-cls_tower.10 |  |
 |
 |
 |
| GradCAM-cls_tower.11 |  |
 |
 |
 |
| GradCAM++-cls_tower.0 |  |
 |
 |
 |
| GradCAM++-cls_tower.1 |  |
 |
 |
 |
| GradCAM++-cls_tower.2 |  |
 |
 |
 |
| GradCAM++-cls_tower.3 |  |
 |
 |
 |
| GradCAM++-cls_tower.4 |  |
 |
 |
 |
| GradCAM++-cls_tower.5 |  |
 |
 |
 |
| GradCAM++-cls_tower.6 |  |
 |
 |
 |
| GradCAM++-cls_tower.7 |  |
 |
 |
 |
| GradCAM++-cls_tower.8 |  |
 |
 |
 |
| GradCAM++-cls_tower.9 |  |
 |
 |
 |
| GradCAM++-cls_tower.10 |  |
 |
 |
 |
| GradCAM++-cls_tower.11 |  |
 |
 |
 |
注：以上分别对proposal_generator.fcos_head.cls_tower..0~head.cls_subnet.11共12个层生成Grad-CAM图，这12层分别对应fcos分类子网络的4层卷积feature map、组标准化后的feature map及ReLu激活后的feature map
不总结了，看图效果吧！
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent