app.py

import torch
import torch.nn as nn
import torch.nn.functional as F
from torchvision import models, transforms
from fastapi import FastAPI, File, UploadFile
from PIL import Image
import io
import numpy as np

# ---------------------------
# App
# ---------------------------
app = FastAPI(title="Rice Leaf Disease Classification API")

# ---------------------------
# Device (CPU for HF Spaces)
# ---------------------------
device = torch.device("cpu")

# ---------------------------
# Load checkpoint
# ---------------------------
checkpoint = torch.load(
    "rice_leaf_model.pth",
    map_location=device
)

class_names = checkpoint["class_names"]
num_classes = checkpoint["num_classes"]

# ---------------------------
# Model
# ---------------------------
model = models.resnet18(pretrained=False)
num_ftrs = model.fc.in_features
model.fc = nn.Linear(num_ftrs, num_classes)

model.load_state_dict(checkpoint["model_state_dict"])
model.to(device)
model.eval()

print("✅ Model loaded successfully")

# ---------------------------
# Image Transform
# ---------------------------
transform = transforms.Compose([
    transforms.Resize((224, 224)),
    transforms.ToTensor(),
    transforms.Normalize(
        mean=[0.485, 0.456, 0.406],
        std=[0.229, 0.224, 0.225]
    )
])

# ---------------------------
# Helper: preprocess image
# ---------------------------
def preprocess_image(image: Image.Image):
    image = image.convert("RGB")
    image = transform(image)
    image = image.unsqueeze(0)
    return image.to(device)

# ---------------------------
# Routes
# ---------------------------
@app.get("/")
def home():
    return {"message": "Rice Leaf Disease API is running 🚀"}

@app.post("/predict")
async def predict(file: UploadFile = File(...)):
    image_bytes = await file.read()
    image = Image.open(io.BytesIO(image_bytes))

    input_tensor = preprocess_image(image)

    with torch.no_grad():
        outputs = model(input_tensor)
        probs = F.softmax(outputs, dim=1)
        confidence, predicted = torch.max(probs, 1)

    predicted_class = class_names[predicted.item()]

    return {
        "predicted_class": predicted_class,
        "confidence": round(confidence.item(), 4)
    }