fix: OCR rupee-symbol-misread-as-8 denomination fix + frozen ₹2000 regression test

app/currency_detector.py

@@ -459,8 +459,16 @@ class CurrencyDetector:
         counts, word_hits = {}, set()
         words = cls._ocr_words(ocr_items)
         for tok in words:
-            stripped = tok.lstrip("₹RS").strip() or tok
-            for cand in {tok, stripped}:
+            stripped = tok.lstrip("₹RS8").strip() or tok
+            # EasyOCR frequently misreads the ₹ glyph as a leading "8" digit
+            # (measured on a real ₹2000 note: "₹2000" -> "82000") — a plain
+            # .lstrip("₹RS") can't catch that since "8" is a real digit, so
+            # try stripping one leading "8" specifically when what remains is
+            # itself a valid denomination length.
+            variants = {tok, stripped}
+            if tok.isdigit() and tok.startswith("8") and len(tok) > 1:
+                variants.add(tok[1:])
+            for cand in variants:
                 if cand.isdigit() and int(cand) in candidates:
                     counts[int(cand)] = counts.get(int(cand), 0) + 1
                     break

test_currency_v2.py

@@ -29,6 +29,7 @@ GEN_DIR = os.path.join(TEST_DIR, "generated")
 REAL = os.path.join(TEST_DIR, "reaal_200rs_1.png")
 FAKE1 = os.path.join(TEST_DIR, "fake1.jpg")
 FAKE2 = os.path.join(TEST_DIR, "fake2.jpg")
+REAL_2000 = os.path.join(TEST_DIR, "Rs2000note.webp")
 
 GENUINE_VERDICTS = {"LIKELY_GENUINE", "GENUINE_FEATURES"}
 FAKE_VERDICTS = {"LIKELY_COUNTERFEIT", "SUSPECT_FEATURES"}
@@ -100,6 +101,10 @@ CASES = [
     ("real_partial", os.path.join(GEN_DIR, "real_partial.png"), None, FAKE_VERDICTS, True),
     # a ₹30 note does not exist — must never clear as genuine
     ("prop_30_note", os.path.join(GEN_DIR, "prop_30_note.png"), None, GENUINE_VERDICTS, False),
+    # genuine ₹2000 (withdrawn denomination) at low resolution — the
+    # denomination is often unreadable via OCR on this exact photo (borderline
+    # confidence), which is fine: it must NEVER read as counterfeit either way
+    ("real_2000", REAL_2000, None, FAKE_VERDICTS, True),
 ]