Update app.py

app.py

@@ -255,26 +255,82 @@ def preprocess_plate_for_ocr(plate_img):
 # ============================================================
 # OCR FUNCTION
 # ============================================================
+# ============================================================
+# IMPROVED LICENSE PLATE OCR
+# ============================================================
 
 def read_license_plate(plate_img):
 
     if reader is None:
-
         return "OCR_UNAVAILABLE"
 
     try:
+        # Convert PIL image to OpenCV image
+        img = np.array(plate_img)
+
+        if img.size == 0:
+            return "UNKNOWN"
 
-        processed = preprocess_plate_for_ocr(
-            plate_img
+        # RGB -> Grayscale
+        gray = cv2.cvtColor(
+            img,
+            cv2.COLOR_RGB2GRAY
         )
 
-        if processed is None:
-            return "UNKNOWN"
+        # --------------------------------------------------------
+        # Enlarge plate image
+        # --------------------------------------------------------
+        gray = cv2.resize(
+            gray,
+            None,
+            fx=4,
+            fy=4,
+            interpolation=cv2.INTER_CUBIC
+        )
+
+        # --------------------------------------------------------
+        # Noise reduction
+        # --------------------------------------------------------
+        gray = cv2.bilateralFilter(
+            gray,
+            9,
+            75,
+            75
+        )
+
+        # --------------------------------------------------------
+        # Improve contrast
+        # --------------------------------------------------------
+        clahe = cv2.createCLAHE(
+            clipLimit=2.0,
+            tileGridSize=(8, 8)
+        )
 
+        gray = clahe.apply(gray)
+
+        # --------------------------------------------------------
+        # Sharpen image
+        # --------------------------------------------------------
+        kernel = np.array([
+            [0, -1, 0],
+            [-1, 5, -1],
+            [0, -1, 0]
+        ])
+
+        sharpened = cv2.filter2D(
+            gray,
+            -1,
+            kernel
+        )
+
+        # --------------------------------------------------------
+        # OCR
+        # --------------------------------------------------------
         results = reader.readtext(
-            processed,
+            sharpened,
             detail=1,
-            paragraph=False
+            paragraph=False,
+            allowlist="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
         )
 
         if not results:
@@ -284,55 +340,111 @@ def read_license_plate(plate_img):
 
         for result in results:
 
-            if len(result) >= 3:
+            if len(result) < 3:
+                continue
 
-                text = str(
-                    result[1]
-                ).strip()
+            text = str(result[1]).upper().strip()
 
-                confidence = float(
-                    result[2]
-                )
+            confidence = float(result[2])
+
+            if confidence < 0.20:
+                continue
 
-                if confidence >= 0.20:
+            # ----------------------------------------------------
+            # Remove spaces and special characters
+            # ----------------------------------------------------
+            cleaned = "".join(
+                char
+                for char in text
+                if char.isalnum()
+            )
+
+            if cleaned == "":
+                continue
 
-                    candidates.append(
-                        (text, confidence)
+            # ----------------------------------------------------
+            # Common OCR corrections
+            # ----------------------------------------------------
+            replacements = {
+                "O": "0",
+                "I": "1",
+                "L": "1",
+                "Z": "2",
+                "S": "5",
+                "B": "8"
+            }
+
+            # Apply corrections only when the character is
+            # surrounded by digits, where OCR commonly confuses
+            # letters and numbers.
+            corrected = ""
+
+            for i, char in enumerate(cleaned):
+
+                if char in replacements:
+
+                    prev_char = (
+                        cleaned[i - 1]
+                        if i > 0
+                        else ""
                     )
 
+                    next_char = (
+                        cleaned[i + 1]
+                        if i < len(cleaned) - 1
+                        else ""
+                    )
+
+                    if (
+                        prev_char.isdigit()
+                        or next_char.isdigit()
+                    ):
+                        char = replacements[char]
+
+                corrected += char
+
+            # ----------------------------------------------------
+            # Keep realistic Indian plate length
+            # ----------------------------------------------------
+            if 4 <= len(corrected) <= 12:
+
+                candidates.append(
+                    (
+                        corrected,
+                        confidence
+                    )
+                )
+
         if not candidates:
             return "UNKNOWN"
 
-        # Select highest-confidence result
+        # Highest-confidence OCR result
         candidates.sort(
             key=lambda x: x[1],
             reverse=True
         )
 
-        text = candidates[0][0]
+        plate_number = candidates[0][0]
 
-        # Remove unwanted characters
-        cleaned = "".join(
-            char
-            for char in text
-            if char.isalnum()
+        # --------------------------------------------------------
+        # Final cleanup
+        # --------------------------------------------------------
+        plate_number = "".join(
+            c
+            for c in plate_number
+            if c.isalnum()
         )
 
-        if cleaned == "":
-            return "UNKNOWN"
-
-        return cleaned.upper()
+        return plate_number.upper()
 
     except Exception as e:
 
         print(
-            "OCR error:",
+            "Improved OCR error:",
             e
         )
 
         return "UNKNOWN"
-
-
 # ============================================================
 # DUPLICATE VEHICLE CHECK
 # ============================================================