Files
breakpilot-lehrer/klausur-service/backend/ocr_pipeline_api.py
Benjamin Admin 587b066a40 feat(ocr-pipeline): ground-truth comparison tool for column detection
Side-by-side view: auto result (readonly) vs GT editor where teacher
draws correct columns. Diff table shows Auto vs GT with IoU matching.
GT data persisted per session for algorithm tuning.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-02-27 22:48:37 +01:00

810 lines
27 KiB
Python

"""
OCR Pipeline API - Schrittweise Seitenrekonstruktion.
Zerlegt den OCR-Prozess in 7 einzelne Schritte:
1. Deskewing - Scan begradigen
2. Dewarping - Buchwoelbung entzerren
3. Spaltenerkennung - Unsichtbare Spalten finden
4. Worterkennung - OCR mit Bounding Boxes
5. Koordinatenzuweisung - Exakte Positionen
6. Seitenrekonstruktion - Seite nachbauen
7. Ground Truth Validierung - Gesamtpruefung
Lizenz: Apache 2.0
DATENSCHUTZ: Alle Verarbeitung erfolgt lokal.
"""
import logging
import time
import uuid
from dataclasses import asdict
from datetime import datetime
from typing import Any, Dict, List, Optional
import cv2
import numpy as np
from fastapi import APIRouter, File, Form, HTTPException, UploadFile
from fastapi.responses import Response
from pydantic import BaseModel
from cv_vocab_pipeline import (
analyze_layout,
analyze_layout_by_words,
create_ocr_image,
deskew_image,
deskew_image_by_word_alignment,
dewarp_image,
dewarp_image_manual,
render_image_high_res,
render_pdf_high_res,
)
from ocr_pipeline_session_store import (
create_session_db,
delete_session_db,
get_session_db,
get_session_image,
init_ocr_pipeline_tables,
list_sessions_db,
update_session_db,
)
logger = logging.getLogger(__name__)
router = APIRouter(prefix="/api/v1/ocr-pipeline", tags=["ocr-pipeline"])
# ---------------------------------------------------------------------------
# In-memory cache for active sessions (BGR numpy arrays for processing)
# DB is source of truth, cache holds BGR arrays during active processing.
# ---------------------------------------------------------------------------
_cache: Dict[str, Dict[str, Any]] = {}
async def _load_session_to_cache(session_id: str) -> Dict[str, Any]:
"""Load session from DB into cache, decoding PNGs to BGR arrays."""
session = await get_session_db(session_id)
if not session:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
if session_id in _cache:
return _cache[session_id]
cache_entry: Dict[str, Any] = {
"id": session_id,
**session,
"original_bgr": None,
"deskewed_bgr": None,
"dewarped_bgr": None,
}
# Decode images from DB into BGR numpy arrays
for img_type, bgr_key in [
("original", "original_bgr"),
("deskewed", "deskewed_bgr"),
("dewarped", "dewarped_bgr"),
]:
png_data = await get_session_image(session_id, img_type)
if png_data:
arr = np.frombuffer(png_data, dtype=np.uint8)
bgr = cv2.imdecode(arr, cv2.IMREAD_COLOR)
cache_entry[bgr_key] = bgr
_cache[session_id] = cache_entry
return cache_entry
def _get_cached(session_id: str) -> Dict[str, Any]:
"""Get from cache or raise 404."""
entry = _cache.get(session_id)
if not entry:
raise HTTPException(status_code=404, detail=f"Session {session_id} not in cache — reload first")
return entry
# ---------------------------------------------------------------------------
# Pydantic Models
# ---------------------------------------------------------------------------
class ManualDeskewRequest(BaseModel):
angle: float
class DeskewGroundTruthRequest(BaseModel):
is_correct: bool
corrected_angle: Optional[float] = None
notes: Optional[str] = None
class ManualDewarpRequest(BaseModel):
shear_degrees: float
class DewarpGroundTruthRequest(BaseModel):
is_correct: bool
corrected_shear: Optional[float] = None
notes: Optional[str] = None
class RenameSessionRequest(BaseModel):
name: str
class ManualColumnsRequest(BaseModel):
columns: List[Dict[str, Any]]
class ColumnGroundTruthRequest(BaseModel):
is_correct: bool
corrected_columns: Optional[List[Dict[str, Any]]] = None
notes: Optional[str] = None
# ---------------------------------------------------------------------------
# Session Management Endpoints
# ---------------------------------------------------------------------------
@router.get("/sessions")
async def list_sessions():
"""List all OCR pipeline sessions."""
sessions = await list_sessions_db()
return {"sessions": sessions}
@router.post("/sessions")
async def create_session(
file: UploadFile = File(...),
name: Optional[str] = Form(None),
):
"""Upload a PDF or image file and create a pipeline session."""
file_data = await file.read()
filename = file.filename or "upload"
content_type = file.content_type or ""
session_id = str(uuid.uuid4())
is_pdf = content_type == "application/pdf" or filename.lower().endswith(".pdf")
try:
if is_pdf:
img_bgr = render_pdf_high_res(file_data, page_number=0, zoom=3.0)
else:
img_bgr = render_image_high_res(file_data)
except Exception as e:
raise HTTPException(status_code=400, detail=f"Could not process file: {e}")
# Encode original as PNG bytes
success, png_buf = cv2.imencode(".png", img_bgr)
if not success:
raise HTTPException(status_code=500, detail="Failed to encode image")
original_png = png_buf.tobytes()
session_name = name or filename
# Persist to DB
await create_session_db(
session_id=session_id,
name=session_name,
filename=filename,
original_png=original_png,
)
# Cache BGR array for immediate processing
_cache[session_id] = {
"id": session_id,
"filename": filename,
"name": session_name,
"original_bgr": img_bgr,
"deskewed_bgr": None,
"dewarped_bgr": None,
"deskew_result": None,
"dewarp_result": None,
"ground_truth": {},
"current_step": 1,
}
logger.info(f"OCR Pipeline: created session {session_id} from {filename} "
f"({img_bgr.shape[1]}x{img_bgr.shape[0]})")
return {
"session_id": session_id,
"filename": filename,
"name": session_name,
"image_width": img_bgr.shape[1],
"image_height": img_bgr.shape[0],
"original_image_url": f"/api/v1/ocr-pipeline/sessions/{session_id}/image/original",
}
@router.get("/sessions/{session_id}")
async def get_session_info(session_id: str):
"""Get session info including deskew/dewarp/column results for step navigation."""
session = await get_session_db(session_id)
if not session:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
# Get image dimensions from original PNG
original_png = await get_session_image(session_id, "original")
if original_png:
arr = np.frombuffer(original_png, dtype=np.uint8)
img = cv2.imdecode(arr, cv2.IMREAD_COLOR)
img_w, img_h = img.shape[1], img.shape[0] if img is not None else (0, 0)
else:
img_w, img_h = 0, 0
result = {
"session_id": session["id"],
"filename": session.get("filename", ""),
"name": session.get("name", ""),
"image_width": img_w,
"image_height": img_h,
"original_image_url": f"/api/v1/ocr-pipeline/sessions/{session_id}/image/original",
"current_step": session.get("current_step", 1),
}
if session.get("deskew_result"):
result["deskew_result"] = session["deskew_result"]
if session.get("dewarp_result"):
result["dewarp_result"] = session["dewarp_result"]
if session.get("column_result"):
result["column_result"] = session["column_result"]
return result
@router.put("/sessions/{session_id}")
async def rename_session(session_id: str, req: RenameSessionRequest):
"""Rename a session."""
updated = await update_session_db(session_id, name=req.name)
if not updated:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
return {"session_id": session_id, "name": req.name}
@router.delete("/sessions/{session_id}")
async def delete_session(session_id: str):
"""Delete a session."""
_cache.pop(session_id, None)
deleted = await delete_session_db(session_id)
if not deleted:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
return {"session_id": session_id, "deleted": True}
# ---------------------------------------------------------------------------
# Image Endpoints
# ---------------------------------------------------------------------------
@router.get("/sessions/{session_id}/image/{image_type}")
async def get_image(session_id: str, image_type: str):
"""Serve session images: original, deskewed, dewarped, binarized, or columns-overlay."""
valid_types = {"original", "deskewed", "dewarped", "binarized", "columns-overlay"}
if image_type not in valid_types:
raise HTTPException(status_code=400, detail=f"Unknown image type: {image_type}")
if image_type == "columns-overlay":
return await _get_columns_overlay(session_id)
# Try cache first for fast serving
cached = _cache.get(session_id)
if cached:
png_key = f"{image_type}_png" if image_type != "original" else None
bgr_key = f"{image_type}_bgr" if image_type != "binarized" else None
# For binarized, check if we have it cached as PNG
if image_type == "binarized" and cached.get("binarized_png"):
return Response(content=cached["binarized_png"], media_type="image/png")
# Load from DB
data = await get_session_image(session_id, image_type)
if not data:
raise HTTPException(status_code=404, detail=f"Image '{image_type}' not available yet")
return Response(content=data, media_type="image/png")
# ---------------------------------------------------------------------------
# Deskew Endpoints
# ---------------------------------------------------------------------------
@router.post("/sessions/{session_id}/deskew")
async def auto_deskew(session_id: str):
"""Run both deskew methods and pick the best one."""
# Ensure session is in cache
if session_id not in _cache:
await _load_session_to_cache(session_id)
cached = _get_cached(session_id)
img_bgr = cached.get("original_bgr")
if img_bgr is None:
raise HTTPException(status_code=400, detail="Original image not available")
t0 = time.time()
# Method 1: Hough Lines
try:
deskewed_hough, angle_hough = deskew_image(img_bgr.copy())
except Exception as e:
logger.warning(f"Hough deskew failed: {e}")
deskewed_hough, angle_hough = img_bgr, 0.0
# Method 2: Word Alignment (needs image bytes)
success_enc, png_orig = cv2.imencode(".png", img_bgr)
orig_bytes = png_orig.tobytes() if success_enc else b""
try:
deskewed_wa_bytes, angle_wa = deskew_image_by_word_alignment(orig_bytes)
except Exception as e:
logger.warning(f"Word alignment deskew failed: {e}")
deskewed_wa_bytes, angle_wa = orig_bytes, 0.0
duration = time.time() - t0
# Pick best method
if abs(angle_wa) >= abs(angle_hough) or abs(angle_hough) < 0.1:
method_used = "word_alignment"
angle_applied = angle_wa
wa_array = np.frombuffer(deskewed_wa_bytes, dtype=np.uint8)
deskewed_bgr = cv2.imdecode(wa_array, cv2.IMREAD_COLOR)
if deskewed_bgr is None:
deskewed_bgr = deskewed_hough
method_used = "hough"
angle_applied = angle_hough
else:
method_used = "hough"
angle_applied = angle_hough
deskewed_bgr = deskewed_hough
# Encode as PNG
success, deskewed_png_buf = cv2.imencode(".png", deskewed_bgr)
deskewed_png = deskewed_png_buf.tobytes() if success else b""
# Create binarized version
binarized_png = None
try:
binarized = create_ocr_image(deskewed_bgr)
success_bin, bin_buf = cv2.imencode(".png", binarized)
binarized_png = bin_buf.tobytes() if success_bin else None
except Exception as e:
logger.warning(f"Binarization failed: {e}")
confidence = max(0.5, 1.0 - abs(angle_applied) / 5.0)
deskew_result = {
"angle_hough": round(angle_hough, 3),
"angle_word_alignment": round(angle_wa, 3),
"angle_applied": round(angle_applied, 3),
"method_used": method_used,
"confidence": round(confidence, 2),
"duration_seconds": round(duration, 2),
}
# Update cache
cached["deskewed_bgr"] = deskewed_bgr
cached["binarized_png"] = binarized_png
cached["deskew_result"] = deskew_result
# Persist to DB
db_update = {
"deskewed_png": deskewed_png,
"deskew_result": deskew_result,
"current_step": 2,
}
if binarized_png:
db_update["binarized_png"] = binarized_png
await update_session_db(session_id, **db_update)
logger.info(f"OCR Pipeline: deskew session {session_id}: "
f"hough={angle_hough:.2f} wa={angle_wa:.2f} -> {method_used} {angle_applied:.2f}")
return {
"session_id": session_id,
**deskew_result,
"deskewed_image_url": f"/api/v1/ocr-pipeline/sessions/{session_id}/image/deskewed",
"binarized_image_url": f"/api/v1/ocr-pipeline/sessions/{session_id}/image/binarized",
}
@router.post("/sessions/{session_id}/deskew/manual")
async def manual_deskew(session_id: str, req: ManualDeskewRequest):
"""Apply a manual rotation angle to the original image."""
if session_id not in _cache:
await _load_session_to_cache(session_id)
cached = _get_cached(session_id)
img_bgr = cached.get("original_bgr")
if img_bgr is None:
raise HTTPException(status_code=400, detail="Original image not available")
angle = max(-5.0, min(5.0, req.angle))
h, w = img_bgr.shape[:2]
center = (w // 2, h // 2)
M = cv2.getRotationMatrix2D(center, angle, 1.0)
rotated = cv2.warpAffine(img_bgr, M, (w, h),
flags=cv2.INTER_LINEAR,
borderMode=cv2.BORDER_REPLICATE)
success, png_buf = cv2.imencode(".png", rotated)
deskewed_png = png_buf.tobytes() if success else b""
# Binarize
binarized_png = None
try:
binarized = create_ocr_image(rotated)
success_bin, bin_buf = cv2.imencode(".png", binarized)
binarized_png = bin_buf.tobytes() if success_bin else None
except Exception:
pass
deskew_result = {
**(cached.get("deskew_result") or {}),
"angle_applied": round(angle, 3),
"method_used": "manual",
}
# Update cache
cached["deskewed_bgr"] = rotated
cached["binarized_png"] = binarized_png
cached["deskew_result"] = deskew_result
# Persist to DB
db_update = {
"deskewed_png": deskewed_png,
"deskew_result": deskew_result,
}
if binarized_png:
db_update["binarized_png"] = binarized_png
await update_session_db(session_id, **db_update)
logger.info(f"OCR Pipeline: manual deskew session {session_id}: {angle:.2f}")
return {
"session_id": session_id,
"angle_applied": round(angle, 3),
"method_used": "manual",
"deskewed_image_url": f"/api/v1/ocr-pipeline/sessions/{session_id}/image/deskewed",
}
@router.post("/sessions/{session_id}/ground-truth/deskew")
async def save_deskew_ground_truth(session_id: str, req: DeskewGroundTruthRequest):
"""Save ground truth feedback for the deskew step."""
session = await get_session_db(session_id)
if not session:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
ground_truth = session.get("ground_truth") or {}
gt = {
"is_correct": req.is_correct,
"corrected_angle": req.corrected_angle,
"notes": req.notes,
"saved_at": datetime.utcnow().isoformat(),
"deskew_result": session.get("deskew_result"),
}
ground_truth["deskew"] = gt
await update_session_db(session_id, ground_truth=ground_truth)
# Update cache
if session_id in _cache:
_cache[session_id]["ground_truth"] = ground_truth
logger.info(f"OCR Pipeline: ground truth deskew session {session_id}: "
f"correct={req.is_correct}, corrected_angle={req.corrected_angle}")
return {"session_id": session_id, "ground_truth": gt}
# ---------------------------------------------------------------------------
# Dewarp Endpoints
# ---------------------------------------------------------------------------
@router.post("/sessions/{session_id}/dewarp")
async def auto_dewarp(session_id: str):
"""Detect and correct vertical shear on the deskewed image."""
if session_id not in _cache:
await _load_session_to_cache(session_id)
cached = _get_cached(session_id)
deskewed_bgr = cached.get("deskewed_bgr")
if deskewed_bgr is None:
raise HTTPException(status_code=400, detail="Deskew must be completed before dewarp")
t0 = time.time()
dewarped_bgr, dewarp_info = dewarp_image(deskewed_bgr)
duration = time.time() - t0
# Encode as PNG
success, png_buf = cv2.imencode(".png", dewarped_bgr)
dewarped_png = png_buf.tobytes() if success else b""
dewarp_result = {
"method_used": dewarp_info["method"],
"shear_degrees": dewarp_info["shear_degrees"],
"confidence": dewarp_info["confidence"],
"duration_seconds": round(duration, 2),
}
# Update cache
cached["dewarped_bgr"] = dewarped_bgr
cached["dewarp_result"] = dewarp_result
# Persist to DB
await update_session_db(
session_id,
dewarped_png=dewarped_png,
dewarp_result=dewarp_result,
auto_shear_degrees=dewarp_info.get("shear_degrees", 0.0),
current_step=3,
)
logger.info(f"OCR Pipeline: dewarp session {session_id}: "
f"method={dewarp_info['method']} shear={dewarp_info['shear_degrees']:.3f} "
f"conf={dewarp_info['confidence']:.2f} ({duration:.2f}s)")
return {
"session_id": session_id,
**dewarp_result,
"dewarped_image_url": f"/api/v1/ocr-pipeline/sessions/{session_id}/image/dewarped",
}
@router.post("/sessions/{session_id}/dewarp/manual")
async def manual_dewarp(session_id: str, req: ManualDewarpRequest):
"""Apply shear correction with a manual angle."""
if session_id not in _cache:
await _load_session_to_cache(session_id)
cached = _get_cached(session_id)
deskewed_bgr = cached.get("deskewed_bgr")
if deskewed_bgr is None:
raise HTTPException(status_code=400, detail="Deskew must be completed before dewarp")
shear_deg = max(-2.0, min(2.0, req.shear_degrees))
if abs(shear_deg) < 0.001:
dewarped_bgr = deskewed_bgr
else:
dewarped_bgr = dewarp_image_manual(deskewed_bgr, shear_deg)
success, png_buf = cv2.imencode(".png", dewarped_bgr)
dewarped_png = png_buf.tobytes() if success else b""
dewarp_result = {
**(cached.get("dewarp_result") or {}),
"method_used": "manual",
"shear_degrees": round(shear_deg, 3),
}
# Update cache
cached["dewarped_bgr"] = dewarped_bgr
cached["dewarp_result"] = dewarp_result
# Persist to DB
await update_session_db(
session_id,
dewarped_png=dewarped_png,
dewarp_result=dewarp_result,
)
logger.info(f"OCR Pipeline: manual dewarp session {session_id}: shear={shear_deg:.3f}")
return {
"session_id": session_id,
"shear_degrees": round(shear_deg, 3),
"method_used": "manual",
"dewarped_image_url": f"/api/v1/ocr-pipeline/sessions/{session_id}/image/dewarped",
}
@router.post("/sessions/{session_id}/ground-truth/dewarp")
async def save_dewarp_ground_truth(session_id: str, req: DewarpGroundTruthRequest):
"""Save ground truth feedback for the dewarp step."""
session = await get_session_db(session_id)
if not session:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
ground_truth = session.get("ground_truth") or {}
gt = {
"is_correct": req.is_correct,
"corrected_shear": req.corrected_shear,
"notes": req.notes,
"saved_at": datetime.utcnow().isoformat(),
"dewarp_result": session.get("dewarp_result"),
}
ground_truth["dewarp"] = gt
await update_session_db(session_id, ground_truth=ground_truth)
if session_id in _cache:
_cache[session_id]["ground_truth"] = ground_truth
logger.info(f"OCR Pipeline: ground truth dewarp session {session_id}: "
f"correct={req.is_correct}, corrected_shear={req.corrected_shear}")
return {"session_id": session_id, "ground_truth": gt}
# ---------------------------------------------------------------------------
# Column Detection Endpoints (Step 3)
# ---------------------------------------------------------------------------
@router.post("/sessions/{session_id}/columns")
async def detect_columns(session_id: str):
"""Run column detection on the dewarped image."""
if session_id not in _cache:
await _load_session_to_cache(session_id)
cached = _get_cached(session_id)
dewarped_bgr = cached.get("dewarped_bgr")
if dewarped_bgr is None:
raise HTTPException(status_code=400, detail="Dewarp must be completed before column detection")
t0 = time.time()
# Binarized image for layout analysis
ocr_img = create_ocr_image(dewarped_bgr)
# Word-based detection (with automatic fallback to projection profiles)
regions = analyze_layout_by_words(ocr_img, dewarped_bgr)
duration = time.time() - t0
columns = [asdict(r) for r in regions]
# Determine classification methods used
methods = list(set(
c.get("classification_method", "") for c in columns
if c.get("classification_method")
))
column_result = {
"columns": columns,
"classification_methods": methods,
"duration_seconds": round(duration, 2),
}
# Persist to DB
await update_session_db(
session_id,
column_result=column_result,
current_step=3,
)
# Update cache
cached["column_result"] = column_result
col_count = len([c for c in columns if c["type"].startswith("column")])
logger.info(f"OCR Pipeline: columns session {session_id}: "
f"{col_count} columns detected ({duration:.2f}s)")
return {
"session_id": session_id,
**column_result,
}
@router.post("/sessions/{session_id}/columns/manual")
async def set_manual_columns(session_id: str, req: ManualColumnsRequest):
"""Override detected columns with manual definitions."""
column_result = {
"columns": req.columns,
"duration_seconds": 0,
"method": "manual",
}
await update_session_db(session_id, column_result=column_result)
if session_id in _cache:
_cache[session_id]["column_result"] = column_result
logger.info(f"OCR Pipeline: manual columns session {session_id}: "
f"{len(req.columns)} columns set")
return {"session_id": session_id, **column_result}
@router.post("/sessions/{session_id}/ground-truth/columns")
async def save_column_ground_truth(session_id: str, req: ColumnGroundTruthRequest):
"""Save ground truth feedback for the column detection step."""
session = await get_session_db(session_id)
if not session:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
ground_truth = session.get("ground_truth") or {}
gt = {
"is_correct": req.is_correct,
"corrected_columns": req.corrected_columns,
"notes": req.notes,
"saved_at": datetime.utcnow().isoformat(),
"column_result": session.get("column_result"),
}
ground_truth["columns"] = gt
await update_session_db(session_id, ground_truth=ground_truth)
if session_id in _cache:
_cache[session_id]["ground_truth"] = ground_truth
return {"session_id": session_id, "ground_truth": gt}
@router.get("/sessions/{session_id}/ground-truth/columns")
async def get_column_ground_truth(session_id: str):
"""Retrieve saved ground truth for column detection, including auto vs GT diff."""
session = await get_session_db(session_id)
if not session:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
ground_truth = session.get("ground_truth") or {}
columns_gt = ground_truth.get("columns")
if not columns_gt:
raise HTTPException(status_code=404, detail="No column ground truth saved")
return {
"session_id": session_id,
"columns_gt": columns_gt,
"columns_auto": session.get("column_result"),
}
async def _get_columns_overlay(session_id: str) -> Response:
"""Generate dewarped image with column borders drawn on it."""
session = await get_session_db(session_id)
if not session:
raise HTTPException(status_code=404, detail=f"Session {session_id} not found")
column_result = session.get("column_result")
if not column_result or not column_result.get("columns"):
raise HTTPException(status_code=404, detail="No column data available")
# Load dewarped image
dewarped_png = await get_session_image(session_id, "dewarped")
if not dewarped_png:
raise HTTPException(status_code=404, detail="Dewarped image not available")
arr = np.frombuffer(dewarped_png, dtype=np.uint8)
img = cv2.imdecode(arr, cv2.IMREAD_COLOR)
if img is None:
raise HTTPException(status_code=500, detail="Failed to decode image")
# Color map for region types (BGR)
colors = {
"column_en": (255, 180, 0), # Blue
"column_de": (0, 200, 0), # Green
"column_example": (0, 140, 255), # Orange
"column_text": (200, 200, 0), # Cyan/Turquoise
"page_ref": (200, 0, 200), # Purple
"column_marker": (0, 0, 220), # Red
"column_ignore": (180, 180, 180), # Light Gray
"header": (128, 128, 128), # Gray
"footer": (128, 128, 128), # Gray
}
overlay = img.copy()
for col in column_result["columns"]:
x, y = col["x"], col["y"]
w, h = col["width"], col["height"]
color = colors.get(col.get("type", ""), (200, 200, 200))
# Semi-transparent fill
cv2.rectangle(overlay, (x, y), (x + w, y + h), color, -1)
# Solid border
cv2.rectangle(img, (x, y), (x + w, y + h), color, 3)
# Label with confidence
label = col.get("type", "unknown").replace("column_", "").upper()
conf = col.get("classification_confidence")
if conf is not None and conf < 1.0:
label = f"{label} {int(conf * 100)}%"
cv2.putText(img, label, (x + 10, y + 30),
cv2.FONT_HERSHEY_SIMPLEX, 0.8, color, 2)
# Blend overlay at 20% opacity
cv2.addWeighted(overlay, 0.2, img, 0.8, 0, img)
success, result_png = cv2.imencode(".png", img)
if not success:
raise HTTPException(status_code=500, detail="Failed to encode overlay image")
return Response(content=result_png.tobytes(), media_type="image/png")