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import torch
import gradio as gr
from torchvision import transforms
# load imagenet labels
with open("imagenet_classes.txt", "r") as f:
categories = [s.strip() for s in f.readlines()]
# load a resnet18 model pretrained on ImageNet
model = torch.hub.load('pytorch/vision:v0.10.0', 'resnet18', pretrained=True)
model.eval()
# preprocess data
pretrained_std = torch.Tensor([0.229, 0.224, 0.225])
pretrained_mean = torch.Tensor([0.485, 0.456, 0.406])
preprocess = transforms.Compose([
transforms.Resize(224),
transforms.CenterCrop(224),
transforms.ToTensor(),
transforms.Normalize(mean=pretrained_mean, std=pretrained_std),
])
def undo_preprocess(processed_img):
img = processed_img.mul(pretrained_std.view(-1,1,1)).add(pretrained_mean.view(-1,1,1))
img = torch.clamp(img, 0, 1).squeeze()
img = img.detach().numpy().transpose(1,2,0)
return img
def set_example_image(img):
return gr.Image.update(value=img[0])
def generate_adversial_image(img, epsilon):
# convert a PIL image to tensor and set requires_grad to True
processed_img = preprocess(img).unsqueeze(0)
processed_img.requires_grad = True
# forward pass
output = model(processed_img)
# get predictions
probs = torch.nn.functional.softmax(output[0], dim=0)
top5_prob, top5_idx = torch.topk(probs, 5)
preds = {categories[idx]: prob.item() for idx, prob in zip(top5_idx, top5_prob)}
# compute gradient
label = torch.Tensor([top5_idx[0]]).type(torch.LongTensor)
loss = torch.nn.functional.cross_entropy(output, label)
model.zero_grad()
loss.backward()
# generate adversarial image
adv_img = processed_img + epsilon*processed_img.grad.data.sign()
adv_output = model(adv_img)
adv_probs = torch.nn.functional.softmax(adv_output[0], dim=0)
adv_top5_prob, adv_top5_idx = torch.topk(adv_probs, 5)
adv_preds = {categories[idx]: prob.item() for idx, prob in zip(adv_top5_idx, adv_top5_prob)}
return undo_preprocess(processed_img), undo_preprocess(adv_img), preds, adv_preds
with gr.Blocks() as demo:
gr.Markdown('''## Generate Adversarial Image with Fast Gradient Sign Method
Given an input image and a neural network, the adversarial image can be generated from
<code>adv_img = input_img + epsilon*input_img.grad</code>
''')
with gr.Box():
input_image = gr.Image(type="pil", label="Input Image")
example_images = gr.Dataset(components=[input_image],
samples=[['coral.jpg'], ['goldfish.jpg'], ['otter.jpg'], ['panda.jpg']])
with gr.Row():
epsilon = gr.Slider(minimum=0, maximum=0.5, value=0.02, step=0.01, label="epsilon")
btn = gr.Button("Generate Adversarial Image")
gr.Markdown('''### Original Image''')
with gr.Box():
with gr.Row():
img_before = gr.Image(label="Original Image")
label_before = gr.Label(label="Original Prediction")
gr.Markdown('''### Adversarial Image''')
with gr.Box():
with gr.Row():
img_after = gr.Image(label="Adversarial Image")
label_after = gr.Label(label="New Prediction")
gr.Markdown('''The prediction is done by ResNet18. Example images are from [Unsplash](https://unsplash.com).''')
# events
btn.click(fn=generate_adversial_image,
inputs=[input_image, epsilon],
outputs=[img_before, img_after, label_before, label_after])
example_images.click(fn=set_example_image,
inputs=example_images,
outputs=example_images.components)
demo.launch()
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