The watermark chip used to be the only GPS control, so turning the watermark
off also stopped the photo from carrying coordinates. Split the two: a GPS
master switch in Settings decides whether the location is read at all, and the
chip decides whether it is drawn on the photo.
0x889d is also written as UTF-8 now — a place name with accents ("TAM KỲ, ĐÀ
NẴNG") was going out latin-1 and reading back as mojibake.
The framing tool matches Make/Model against its known-device list and prints
the place name; a CameraX capture only carried the raw model codename
(2203121C) and no 0x9a00/0x889d, which is what a stock camera photo always
has. State the market name plus the geotag locality, and leave a source that
already carries 0x9a00 untouched so a library photo of another device is
never relabelled.
HyperOS Gallery reads EXIF 0x889e (a JSON blob) to build its watermark
frame; without it a photo fails with "cannot recognize the parameters".
CameraX/HAL never supplies that vendor tag, so a capture from this app
lacked it while a stock-camera photo carried it.
Read back the same props the stock camera derives the blob from
(ro.product.device / ro.product.marketname / Build.MANUFACTURER) via the
native module, synthesize the blob in exifWrite, and write it only when
the source has none and the device is Xiaomi/Redmi/POCO - a source blob
is never overwritten.
Match the layout the sample camera file uses: a fourth Interoperability IFD
(0xa005 = R98/0100) and the baseline tags the emulator HAL omits (ExifVersion
0230, FlashPixVersion 0100, ComponentsConfiguration, ColorSpace), plus the
OffsetTime/OffsetTimeOriginal/OffsetTimeDigitized tags for shots this app
timestamps. Source-owned tags are still kept as-is.
Also fix swapToLittleEndian: Buffer.slice() aliases, so the big-endian swap was
mutating the caller's bytes (a Xiaomi source read back as ISO 36865 instead of
400). Use new Uint8Array(data).
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