Saliency

Visualize Saliency Maps & Class Activation Maps

Implement the Guided-ReLU visualization used in the paper:

• Striving for Simplicity: The All Convolutional Net

And the class activation mapping (CAM) visualization proposed in the paper:

• Learning Deep Features for Discriminative Localization

Saliency Maps

saliency-maps.py takes an image, and produce its saliency map by running a ResNet-50 and backprop its maximum activations back to the input image space. Similar techinques can be used to visualize the concept learned by each filter in the network.

Usage:

wget http://download.tensorflow.org/models/resnet_v1_50_2016_08_28.tar.gz
tar -xzvf resnet_v1_50_2016_08_28.tar.gz
./saliency-maps.py cat.jpg

Left to right:

• the original cat image
• the magnitude in the saliency map
• the magnitude blended with the original image
• positive correlated pixels (keep original color)
• negative correlated pixels (keep original color)

CAM

CAM-resnet.py fine-tune a Preact-ResNet to have 2x larger last-layer feature maps, then produce CAM visualizations.

Usage:

1. Fine tune or retrain the ResNet:

./CAM-resnet.py --data /path/to/imagenet [--load ImageNet-ResNet18-Preact.npz] [--gpu 0,1,2,3]

Pretrained and fine-tuned ResNet can be downloaded in the model zoo.

2. Generate CAM on ImageNet validation set:

./CAM-resnet.py --data /path/to/imagenet --load ImageNet-ResNet18-Preact-2xGAP.npz --cam