337 lines
12 KiB
Python
337 lines
12 KiB
Python
"""
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app/utils/photo_stamp.py
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------------------------
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Burn a capture-time + geolocation overlay into uploaded evidence photos.
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Applied at UPLOAD time (``app/api/photos.py``) rather than on
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``PATCH /issues/<id>/photos``. At upload the raw bytes and any camera EXIF are
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in hand, so nothing has to be read back out of R2, and each upload writes
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exactly one already-stamped object. That also keeps stamping clear of the
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retry/double-burn hazard the PATCH endpoint would have — it is deliberately
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idempotent and re-runnable (CLAUDE.md rule 45), so burning there could stack a
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second bar onto an already-stamped image.
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Metadata resolution order
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-------------------------
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1. Client-supplied ``captured_at`` / ``latitude`` / ``longitude`` — most
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reliable for an offline-first app: the iPad knows when and where the shot
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was taken even if it syncs hours later.
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2. The image's own EXIF ``DateTimeOriginal`` / ``GPSInfo``.
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3. Server receipt time (last resort; no geo).
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FAILURE POLICY
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--------------
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Stamping must never cost us the photo. Every failure path falls back to
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storing the original bytes unmodified — an unstamped photo beats a lost one.
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"""
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import io
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import logging
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from datetime import datetime
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import pytz
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from app.utils.time_utils import EASTERN, now_eastern
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logger = logging.getLogger(__name__)
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# Only these are stamped. GIF (possibly animated) and anything exotic passes
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# through untouched rather than risking a broken re-encode.
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_STAMPABLE_FORMATS = {'JPEG', 'PNG'}
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# Candidate TrueType fonts, in preference order. Pillow does not reliably ship
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# a TTF, and the bitmap default is unreadably small on a 4000px photo, so we
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# probe the usual Linux locations and degrade gracefully.
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_FONT_CANDIDATES = (
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'/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf',
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'/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf',
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'/usr/share/fonts/truetype/liberation/LiberationSans-Bold.ttf',
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'/usr/share/fonts/truetype/freefont/FreeSansBold.ttf',
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'C:/Windows/Fonts/arialbd.ttf',
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'C:/Windows/Fonts/arial.ttf',
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)
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_EXIF_DATETIME_ORIGINAL = 36867 # 0x9003
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_EXIF_DATETIME_DIGITIZED = 36868 # 0x9004
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_EXIF_DATETIME = 306 # 0x0132
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_EXIF_GPS_IFD = 34853 # 0x8825
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# ── Font ──────────────────────────────────────────────────────────────────────
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def _load_font(size):
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"""Return a TrueType font at *size*, or Pillow's bitmap default."""
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from PIL import ImageFont
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for path in _FONT_CANDIDATES:
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try:
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return ImageFont.truetype(path, size)
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except Exception:
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continue
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try:
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# Pillow >= 9.2 can scale the default font.
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return ImageFont.load_default(size=size)
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except Exception:
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return ImageFont.load_default()
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# ── Metadata extraction ───────────────────────────────────────────────────────
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def _parse_client_datetime(value):
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"""Parse a client ISO-8601 timestamp into naive Eastern, or None.
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Accepts offsets and a trailing 'Z'. An offset-aware value is converted to
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Eastern; a naive value is taken as already-Eastern wall time.
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"""
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if not value:
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return None
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text = str(value).strip()
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if not text:
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return None
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if text.endswith(('Z', 'z')):
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text = text[:-1] + '+00:00'
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try:
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dt = datetime.fromisoformat(text)
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except ValueError:
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return None
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if dt.tzinfo is not None:
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dt = dt.astimezone(EASTERN).replace(tzinfo=None)
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return dt
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def _parse_exif_datetime(raw):
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"""Parse an EXIF 'YYYY:MM:DD HH:MM:SS' string into a naive datetime."""
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if not raw:
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return None
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try:
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return datetime.strptime(str(raw).strip(), '%Y:%m:%d %H:%M:%S')
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except (ValueError, TypeError):
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return None
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def _exif_datetime(exif):
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"""Best available capture time from EXIF, or None."""
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if not exif:
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return None
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for tag in (_EXIF_DATETIME_ORIGINAL, _EXIF_DATETIME_DIGITIZED, _EXIF_DATETIME):
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dt = _parse_exif_datetime(exif.get(tag))
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if dt:
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return dt
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return None
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def _dms_to_decimal(dms, ref):
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"""Convert EXIF degrees/minutes/seconds rationals to signed decimal."""
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try:
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deg, minutes, seconds = (float(x) for x in dms)
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except (TypeError, ValueError):
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return None
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value = deg + minutes / 60.0 + seconds / 3600.0
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if str(ref).upper().strip() in ('S', 'W'):
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value = -value
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return value
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def _exif_gps(exif):
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"""Return (lat, lng) decimal degrees from EXIF GPSInfo, or (None, None)."""
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if not exif:
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return (None, None)
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try:
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gps = exif.get_ifd(_EXIF_GPS_IFD)
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except Exception:
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gps = None
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if not gps:
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return (None, None)
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# 1/2 = LatitudeRef/Latitude, 3/4 = LongitudeRef/Longitude
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lat = _dms_to_decimal(gps.get(2), gps.get(1)) if gps.get(2) and gps.get(1) else None
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lng = _dms_to_decimal(gps.get(4), gps.get(3)) if gps.get(4) and gps.get(3) else None
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return (lat, lng)
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def _coerce_coord(value):
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"""Parse a coordinate to float, rejecting out-of-range/garbage values."""
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if value is None or value == '':
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return None
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try:
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num = float(value)
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except (TypeError, ValueError):
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return None
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if num != num or abs(num) > 180: # NaN or impossible
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return None
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return num
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def resolve_metadata(exif, captured_at=None, latitude=None, longitude=None):
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"""Resolve (capture_dt, lat, lng, source) from client fields then EXIF.
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``source`` is one of 'client', 'exif', or 'server' and describes where the
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*timestamp* came from — useful for logging and for judging trust later.
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"""
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dt = _parse_client_datetime(captured_at)
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source = 'client' if dt else None
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lat = _coerce_coord(latitude)
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lng = _coerce_coord(longitude)
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if dt is None:
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dt = _exif_datetime(exif)
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source = 'exif' if dt else None
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if lat is None or lng is None:
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ex_lat, ex_lng = _exif_gps(exif)
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lat = lat if lat is not None else ex_lat
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lng = lng if lng is not None else ex_lng
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if dt is None:
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dt = now_eastern()
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source = 'server'
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return dt, lat, lng, source
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# ── Overlay rendering ─────────────────────────────────────────────────────────
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def _tz_abbrev(dt):
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"""EDT/EST label for a naive Eastern datetime."""
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try:
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return EASTERN.localize(dt).strftime('%Z')
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except Exception:
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return 'ET'
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def _overlay_lines(dt, lat, lng):
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"""Text lines for the overlay bar."""
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lines = [f"{dt.strftime('%Y-%m-%d %H:%M:%S')} {_tz_abbrev(dt)}"]
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if lat is not None and lng is not None:
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lines.append(f'{lat:.5f}, {lng:.5f}')
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return lines
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def _draw_overlay(img, lines):
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"""Draw a translucent bar with *lines* across the bottom of *img*."""
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from PIL import Image, ImageDraw
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if img.mode not in ('RGB', 'RGBA'):
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img = img.convert('RGB')
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width, height = img.size
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# Scale everything off the short edge so portrait and landscape match.
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base = min(width, height)
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font_size = max(11, int(base * 0.020))
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pad = max(6, int(base * 0.012))
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font = _load_font(font_size)
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measure = ImageDraw.Draw(img)
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# Measure the block.
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heights, widths = [], []
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for line in lines:
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box = measure.textbbox((0, 0), line, font=font)
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widths.append(box[2] - box[0])
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heights.append(box[3] - box[1])
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line_gap = max(2, int(font_size * 0.25))
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text_h = sum(heights) + line_gap * (len(lines) - 1)
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bar_h = text_h + pad * 2
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# Draw the whole overlay on a transparent layer so both the bar AND the
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# text carry alpha, then composite once. Keeps the photo readable through
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# the stamp instead of masking it behind a solid strip.
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layer = Image.new('RGBA', (width, bar_h), (0, 0, 0, 0))
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draw = ImageDraw.Draw(layer)
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draw.rectangle((0, 0, width, bar_h), fill=(0, 0, 0, 80))
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y = pad
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for line, h in zip(lines, heights):
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# Faint dark outline still keeps the text legible over a bright photo.
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for dx, dy in ((-1, 0), (1, 0), (0, -1), (0, 1)):
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draw.text((pad + dx, y + dy), line, font=font, fill=(0, 0, 0, 90))
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draw.text((pad, y), line, font=font, fill=(255, 255, 255, 165))
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y += h + line_gap
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if img.mode == 'RGBA':
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img.alpha_composite(layer, (0, height - bar_h))
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else:
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img.paste(Image.alpha_composite(
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img.crop((0, height - bar_h, width, height)).convert('RGBA'), layer
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).convert('RGB'), (0, height - bar_h))
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return img
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# ── Public API ────────────────────────────────────────────────────────────────
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def stamp_image_bytes(data, captured_at=None, latitude=None, longitude=None):
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"""Burn the capture-time/geo overlay into *data*.
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Returns ``(out_bytes, meta)``. On any failure — unsupported format, corrupt
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image, missing Pillow — returns the ORIGINAL bytes with ``meta['stamped']``
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False rather than raising, so an upload is never lost to a stamping bug.
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"""
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meta = {'stamped': False, 'captured_at': None, 'latitude': None,
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'longitude': None, 'source': None}
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try:
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from PIL import Image, ImageOps
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img = Image.open(io.BytesIO(data))
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fmt = (img.format or '').upper()
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try:
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exif = img.getexif()
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except Exception:
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exif = None
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dt, lat, lng, source = resolve_metadata(exif, captured_at, latitude, longitude)
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meta.update({'captured_at': dt, 'latitude': lat,
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'longitude': lng, 'source': source})
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if fmt not in _STAMPABLE_FORMATS:
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logger.info('PHOTO STAMP | skipped unsupported format=%s', fmt or '?')
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return data, meta
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# Honour the camera's EXIF orientation BEFORE drawing, otherwise the
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# bar lands on a rotated edge and the re-encode (which drops EXIF)
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# would leave the photo visibly rotated versus the original.
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img = ImageOps.exif_transpose(img)
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img = _draw_overlay(img, _overlay_lines(dt, lat, lng))
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out = io.BytesIO()
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if fmt == 'JPEG':
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if img.mode != 'RGB':
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img = img.convert('RGB')
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img.save(out, format='JPEG', quality=88, optimize=True)
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else:
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img.save(out, format='PNG', optimize=True)
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meta['stamped'] = True
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return out.getvalue(), meta
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except Exception as exc: # never lose a photo
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logger.warning('PHOTO STAMP | failed, storing original: %s', exc)
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return data, meta
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def stamp_file_storage(file_obj, captured_at=None, latitude=None, longitude=None):
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"""Return a FileStorage of the stamped image, plus the resolved metadata.
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The result is a drop-in replacement for the incoming upload: it keeps the
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original ``filename``/``content_type``, so ``storage.save()`` derives the
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same key and works unchanged on both the local and s3 backends.
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"""
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from werkzeug.datastructures import FileStorage
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file_obj.stream.seek(0)
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original = file_obj.stream.read()
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out_bytes, meta = stamp_image_bytes(
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original, captured_at=captured_at, latitude=latitude, longitude=longitude
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)
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if not meta['stamped']:
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file_obj.stream.seek(0) # hand back the untouched upload
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return file_obj, meta
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return FileStorage(
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stream=io.BytesIO(out_bytes),
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filename=file_obj.filename,
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content_type=file_obj.content_type,
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), meta
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