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32800ec | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 | """Image / audio decoding helpers."""
from __future__ import annotations
import base64
import io
from typing import Optional
import numpy as np
from PIL import Image
def decode_base64_image(b64: str) -> bytes:
"""Decode a base64 string to raw image bytes.
Strips data URL prefix if present.
Raises ValueError on bad input.
"""
if not b64:
raise ValueError("empty base64 image")
if "," in b64 and b64.startswith("data:"):
b64 = b64.split(",", 1)[1]
try:
return base64.b64decode(b64, validate=True)
except Exception as exc:
raise ValueError(f"invalid base64: {exc}") from exc
def decode_base64_audio(b64: str) -> bytes:
"""Decode a base64 string to raw audio bytes."""
if not b64:
raise ValueError("empty base64 audio")
if "," in b64 and b64.startswith("data:"):
b64 = b64.split(",", 1)[1]
try:
return base64.b64decode(b64, validate=True)
except Exception as exc:
raise ValueError(f"invalid base64: {exc}") from exc
def image_to_pil(data: bytes) -> Image.Image:
"""Decode image bytes to a PIL Image. Raises ValueError on failure."""
try:
img = Image.open(io.BytesIO(data))
img.load()
if img.mode not in ("RGB", "RGBA", "L"):
img = img.convert("RGB")
return img
except Exception as exc:
raise ValueError(f"could not decode image: {exc}") from exc
def perceptual_hash(data: bytes, size: int = 16) -> str:
"""Compute a perceptual hash of an image for cache lookup.
Returns a 64-char hex string. Robust to small JPEG re-encodes
and minor color shifts.
"""
img = image_to_pil(data).convert("L").resize((size + 1, size))
pixels = np.asarray(img, dtype=np.float32)
diff = pixels[:, 1:] > pixels[:, :-1]
bits = diff.flatten()
h = 0
for bit in bits:
h = (h << 1) | int(bit)
return format(h, f"0{size*size // 4}x")
def audio_size_hash(data: bytes) -> str:
"""Cheap audio hash: size + first/last 1KB + sha-like prefix."""
import hashlib
h = hashlib.sha256()
h.update(len(data).to_bytes(8, "big"))
h.update(data[:1024])
h.update(data[-1024:])
return h.hexdigest()[:32]
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