EdgeAI_Digit_Recognition/inference.py

import threading
import queue
import time
import logging
import cv2
import numpy as np
import tflite_runtime.interpreter as tflite
from config import Config

logger = logging.getLogger(__name__)

class InferenceWorker:
    def __init__(self):
        self.input_queue = queue.Queue(maxsize=10)
        self.result_queue = queue.Queue()
        self.running = False
        self.interpreter = None
        self.input_details = None
        self.output_details = None

        self.lock = threading.Lock()
        
        # Load Model
        self.load_model()

    def load_model(self):
        try:
            logger.info(f"Loading TFLite model from: {Config.MODEL_PATH}")
            self.interpreter = tflite.Interpreter(model_path=Config.MODEL_PATH)
            self.interpreter.allocate_tensors()
            self.input_details = self.interpreter.get_input_details()
            self.output_details = self.interpreter.get_output_details()
            
            # Store original input shape for resizing logic
            self.original_input_shape = self.input_details[0]['shape']
            logger.info(f"Model loaded. Default input shape: {self.original_input_shape}")
            
        except Exception as e:
            logger.critical(f"Failed to load TFLite model: {e}")
            self.interpreter = None

    def start(self):
        if self.running: return
        self.running = True
        threading.Thread(target=self._worker_loop, daemon=True).start()
        logger.info("Inference worker started.")

    def add_task(self, camera_id, rois, frame):
        """Add task (non-blocking)."""
        if not self.interpreter: return
        try:
            task = {
                'camera_id': camera_id,
                'rois': rois,
                'frame': frame,
                'timestamp': time.time()
            }
            self.input_queue.put(task, block=False)
        except queue.Full:
            pass

    def get_result(self):
        try:
            return self.result_queue.get(block=False)
        except queue.Empty:
            return None

    def _worker_loop(self):
        while self.running:
            try:
                task = self.input_queue.get(timeout=1)
            except queue.Empty:
                continue

            cam_id = task['camera_id']
            rois = task['rois']
            frame = task['frame']

            try:
                # 1. Crop all ROIs
                crops = self._crop_rois(frame, rois)
                if not crops: continue

                # 2. Batch Predict (Optimized Step)
                digits = self.predict_batch(crops)

                # 3. Combine
                valid_digits = [d for d in digits if d.isdigit()]
                if len(valid_digits) == len(digits) and len(valid_digits) > 0:
                    final_number = int("".join(valid_digits))
                    
                    self.result_queue.put({
                        'camera_id': cam_id,
                        'value': final_number,
                        'digits': valid_digits
                    })
                    
            except Exception as e:
                logger.error(f"Inference error for {cam_id}: {e}")

    def _crop_rois(self, image, roi_list):
        cropped_images = []
        for roi in roi_list:
            try:
                x, y, w, h = roi['x'], roi['y'], roi['width'], roi['height']
                cropped = image[y:y+h, x:x+w]
                if cropped.size > 0:
                    cropped_images.append(cropped)
            except Exception:
                pass
        return cropped_images

    def predict_batch(self, images):
        """Run inference on a batch of images at once."""
        with self.lock:              # <--- Add this wrapper
            if not self.interpreter: return []
            
            num_images = len(images)
            if num_images == 0: return []

            input_index = self.input_details[0]['index']
            output_index = self.output_details[0]['index']

            # Preprocess all images into a single batch array
            # Shape: [N, 32, 20, 3] (assuming model expects 32x20 rgb)
            batch_input = []
            
            target_h, target_w = 32, 20  # Based on your previous code logic
            
            for img in images:
                # Resize
                roi_resized = cv2.resize(img, (target_w, target_h))
                # Color
                roi_rgb = cv2.cvtColor(roi_resized, cv2.COLOR_BGR2RGB)
                # Normalize
                roi_norm = roi_rgb.astype(np.float32)
                batch_input.append(roi_norm)
            
            # Create batch tensor
            input_tensor = np.array(batch_input)
            
            # --- DYNAMIC RESIZING ---
            # TFLite models have a fixed input size (usually batch=1).
            # We must resize the input tensor to match our current batch size (N).
            
            # 1. Resize input tensor
            self.interpreter.resize_tensor_input(input_index, [num_images, target_h, target_w, 3])
            
            # 2. Re-allocate tensors (This is expensive! See note below)
            self.interpreter.allocate_tensors()
            
            # 3. Run Inference
            self.interpreter.set_tensor(input_index, input_tensor)
            self.interpreter.invoke()
            
            # 4. Get Results
            output_data = self.interpreter.get_tensor(output_index)
            
            # Result shape is [N, 10] (probabilities for 10 digits)
            predictions = []
            for i in range(num_images):
                digit_class = np.argmax(output_data[i])
                predictions.append(str(digit_class))
                
            return predictions