Bug: Resize does not preserve XMP metadata

[thadwald]

All the information is in the title.

[pierotofy]

Thanks for reporting this; it's something I should really fix this one of these days. It involves adding exiftool to the codebase because any other library is just not going to cut it, but 100% doable.

[kikislater]

It is possible without exiftool with python package exifread

[pierotofy]

Can you post an example?

[kikislater]

My apologies, I didn't use exifread but PIL, xmltodict, xml and struct

import xmltodict as x2d
from xml.parsers.expat import ExpatError
from PIL import Image
from PIL.Image import Exif
import struct

def resize_with_exif(src, dst, max_size=2048):
    img = Image.open(src)
    exif = img.getexif()
    w, h = img.size
    scale = min(max_size / w, max_size / h, 1.0)
    new_size = (int(w * scale), int(h * scale))

    img = img.resize(new_size, Image.LANCZOS)
    img.save(dst, "JPEG", exif=exif, quality=75, subsampling=0)

def extract_xmp_bytes(fp):
    data = fp.read()
    start = data.find(b'<x:xmpmeta')
    end = data.find(b'</x:xmpmeta')
    if start != -1 and end != -1:
        return data[start:end + 12]
    return None

def build_xmp_app1(xmp_bytes):
    identifier = b"http://ns.adobe.com/xap/1.0/\x00"
    payload = identifier + xmp_bytes
    length = len(payload) + 2  # length field includes itself
    return b"\xFF\xE1" + struct.pack(">H", length) + payload

def inject_xmp_valid(jpeg_path, xmp_bytes):
    with open(jpeg_path, "rb") as f:
        data = f.read()

    if not data.startswith(b"\xFF\xD8"):
        raise ValueError("Not a JPEG")

    app1 = build_xmp_app1(xmp_bytes)

    # Insert after SOI (FFD8)
    out = data[:2] + app1 + data[2:]

    with open(jpeg_path, "wb") as f:
        f.write(out)
    
src = "/home/sylvain/SIG/GEOBASE/DRONE/IRD/carto_sancho/DJI_0145.JPG"
dst = "/tmp/DJI_0145_resized.JPG"

with open(src, "rb") as f:
    xmp_bytes = extract_xmp_bytes(f)

resize_with_exif(src, dst, 2048)
inject_xmp_valid(dst, xmp_bytes)