app.py

from fastapi import FastAPI
from fastapi.staticfiles import StaticFiles
from fastapi.responses import FileResponse
import io, base64
import torch
import torch.nn as nn
import torchvision.transforms as transforms
from PIL import Image, ImageOps

# ----------------------------------------
# 1. Create the FastAPI app FIRST
# ----------------------------------------
app = FastAPI()

from fastapi.middleware.cors import CORSMiddleware

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# ----------------------------------------
# 2. Serve index.html (no static folder needed)
# ----------------------------------------
@app.get("/")
def serve_home():
    return FileResponse("index.html")


# ----------------------------------------
# 3. Your model definition
# ----------------------------------------
class LeNet5(nn.Module):
    def __init__(self, num_classes=10):
        super().__init__()
        self.layer1 = nn.Sequential(
            nn.Conv2d(1, 6, 5),
            nn.BatchNorm2d(6),
            nn.ReLU(),
            nn.MaxPool2d(2)
        )
        self.layer2 = nn.Sequential(
            nn.Conv2d(6, 16, 5),
            nn.BatchNorm2d(16),
            nn.ReLU(),
            nn.MaxPool2d(2)
        )
        self.flatten = nn.Flatten()
        self.fc = nn.Linear(16 * 5 * 5, 120)
        self.fc1 = nn.Linear(120, 84)
        self.fc2 = nn.Linear(84, num_classes)
        self.relu = nn.ReLU()

    def forward(self, x):
        x = self.layer1(x)
        x = self.layer2(x)
        x = self.flatten(x)
        x = self.relu(self.fc(x))
        x = self.relu(self.fc1(x))
        return self.fc2(x)

model = LeNet5()
model.load_state_dict(torch.load("lenet5.pth", map_location="cpu"))
model.eval()


# ----------------------------------------
# 4. Predict route (base64 image)
# ----------------------------------------
from pydantic import BaseModel

class CanvasImage(BaseModel):
    image: str

@app.post("/predict")
async def predict_digit(data: CanvasImage):
    img_data = data.image.split(",")[1]
    img_bytes = base64.b64decode(img_data)
    image = Image.open(io.BytesIO(img_bytes)).convert("L")

    image = image.resize((28, 28))
    image = ImageOps.invert(image)

    transform = transforms.Compose([
        transforms.ToTensor(),
        transforms.Normalize((0.1307,), (0.3081,))
    ])

    img = transform(image).unsqueeze(0)
    img = torch.nn.functional.pad(img, (2,2,2,2))

    with torch.no_grad():
        output = model(img)
        pred = output.argmax(1).item()

    return {"prediction": pred}