app.py

from io import BytesIO

import matplotlib.pyplot as plt
import requests
import streamlit as st
import torch
from PIL import Image
from torchvision import models
from torchvision.transforms.functional import normalize, resize, to_pil_image, to_tensor

from torchcam import methods
from torchcam.methods._utils import locate_candidate_layer
from torchcam.utils import overlay_mask

CAM_METHODS = ["CAM", "GradCAM", "GradCAMpp", "SmoothGradCAMpp", "ScoreCAM", "SSCAM", "ISCAM", "XGradCAM", "LayerCAM"]
TV_MODELS = [
    "resnet18",
    "resnet50",
    "mobilenet_v3_small",
    "mobilenet_v3_large",
    "regnet_y_400mf",
    "convnext_tiny",
    "convnext_small",
]
LABEL_MAP = requests.get(
    "https://raw.githubusercontent.com/anishathalye/imagenet-simple-labels/master/imagenet-simple-labels.json"
).json()


def main():

    # Wide mode
    st.set_page_config(layout="wide")

    # Designing the interface
    st.title("TorchCAM: class activation explorer")
    # For newline
    st.write("\n")
    # Set the columns
    cols = st.columns((1, 1, 1))
    cols[0].header("Input image")
    cols[1].header("Raw CAM")
    cols[-1].header("Overlayed CAM")

    # Sidebar
    # File selection
    st.sidebar.title("Input selection")
    # Disabling warning
    st.set_option("deprecation.showfileUploaderEncoding", False)
    # Choose your own image
    uploaded_file = st.sidebar.file_uploader("Upload files", type=["png", "jpeg", "jpg"])
    if uploaded_file is not None:
        img = Image.open(BytesIO(uploaded_file.read()), mode="r").convert("RGB")

        cols[0].image(img, use_column_width=True)

    # Model selection
    st.sidebar.title("Setup")
    tv_model = st.sidebar.selectbox(
        "Classification model",
        TV_MODELS,
        help="Supported models from Torchvision",
    )
    default_layer = ""
    if tv_model is not None:
        with st.spinner("Loading model..."):
            model = models.__dict__[tv_model](pretrained=True).eval()
        default_layer = locate_candidate_layer(model, (3, 224, 224))

    if torch.cuda.is_available():
        model = model.cuda()

    target_layer = st.sidebar.text_input(
        "Target layer",
        default_layer,
        help='If you want to target several layers, add a "+" separator (e.g. "layer3+layer4")',
    )
    cam_method = st.sidebar.selectbox(
        "CAM method",
        CAM_METHODS,
        help="The way your class activation map will be computed",
    )
    if cam_method is not None:
        cam_extractor = methods.__dict__[cam_method](
            model, target_layer=[s.strip() for s in target_layer.split("+")] if len(target_layer) > 0 else None
        )

    class_choices = [f"{idx + 1} - {class_name}" for idx, class_name in enumerate(LABEL_MAP)]
    class_selection = st.sidebar.selectbox("Class selection", ["Predicted class (argmax)"] + class_choices)

    # For newline
    st.sidebar.write("\n")

    if st.sidebar.button("Compute CAM"):

        if uploaded_file is None:
            st.sidebar.error("Please upload an image first")

        else:
            with st.spinner("Analyzing..."):

                # Preprocess image
                img_tensor = normalize(to_tensor(resize(img, (224, 224))), [0.485, 0.456, 0.406], [0.229, 0.224, 0.225])

                if torch.cuda.is_available():
                    img_tensor = img_tensor.cuda()

                # Forward the image to the model
                out = model(img_tensor.unsqueeze(0))
                # Select the target class
                if class_selection == "Predicted class (argmax)":
                    class_idx = out.squeeze(0).argmax().item()
                else:
                    class_idx = LABEL_MAP.index(class_selection.rpartition(" - ")[-1])
                # Retrieve the CAM
                act_maps = cam_extractor(class_idx, out)
                # Fuse the CAMs if there are several
                activation_map = act_maps[0] if len(act_maps) == 1 else cam_extractor.fuse_cams(act_maps)
                # Plot the raw heatmap
                fig, ax = plt.subplots()
                ax.imshow(activation_map.squeeze(0).cpu().numpy())
                ax.axis("off")
                cols[1].pyplot(fig)

                # Overlayed CAM
                fig, ax = plt.subplots()
                result = overlay_mask(img, to_pil_image(activation_map, mode="F"), alpha=0.5)
                ax.imshow(result)
                ax.axis("off")
                cols[-1].pyplot(fig)


if __name__ == "__main__":
    main()