- tool_gaussian_blur: Gaussian blur denoising, suitable for noisy plates
- tool_grayscale: Convert to grayscale, simplifies downstream processing
- tool_binarize_otsu: OTSU binarization, separates foreground/background
- tool_edge_detect_canny: Canny edge detection
- tool_affine_correct: Affine transform tilt correction
- tool_tesseract_ocr: Tesseract 5.4 whole-plate recognition (chi_sim+eng)
- tool_lookup_confusion: Query confusion character mapping table
- tool_search_blacklist: Query blacklist database
- After dual-channel OCR, prefer the result with more recognized characters
- Same character count: prefer higher confidence
- One channel fails: use the other
- Gaussian blur kernel=5 is the key parameter
- Return ONLY the plate number string, no extra text
- Failed plates: return "recognition failed"
- Do NOT include JSON, markdown formatting, or explanations