The media pipeline is kind-aware, writes the file before the row, and strips metadata

Context

An app that stores images on the device has four problems that all look like one:

1. Memory. A 12 MP camera shot decoded at full size is ~48 MB of bitmap. A grid of them is an OOM crash on a mid-range phone.
2. Orientation. Cameras commonly leave pixels unrotated and record an EXIF orientation tag instead. Coil honours that tag on an untouched file — but re-encoding discards the tag and keeps the pixels sideways, so camera-taken images come out rotated while album-picked ones do not.
3. Privacy. A camera stamps GPS coordinates on every shot. An app that copies those into a backup is exporting the user’s home address.
4. Portability. An absolute path changes across installs, so every restored backup points at files that are not there.

Decision

One function persists every image: MediaFiles.persist(uri, kind). Nothing else writes an image file, ever.

The kind selects both the directory and the downsample spec, because the needs genuinely differ: a thumbnail wants a small centre-cropped square, a photo a large long-edge cap, and a document downsampled to photo dimensions makes small print unreadable. The directory doubles as the backup export scope, so scopes are a list of MediaKind rather than a list of magic strings.

Decode at roughly the size needed (inSampleSize), apply the EXIF orientation to the pixels, re-encode as JPEG. Bitmap.compress writes pixels only, so every EXIF tag — GPS included — is gone by construction rather than by a removal step someone could forget.

The capture date is read on the way past and returned, because there is no going back: a column added later could never be backfilled from files whose metadata has already been stripped.

The file is written before the row, and paths stored on the row are relative.

Alternatives

Store the original and downsample at draw time. Costs the memory on every render instead of once, and the backup carries full-resolution originals.

Strip EXIF as a separate step. A step that can be skipped will be skipped. Re-encoding makes it structural.

Row first, then file. A crash in between leaves a dangling path, which to the user looks exactly like the app losing their photo. File first leaves an invisible orphan, which costs disk and nothing else — and “missing media renders as a placeholder” already covers the other direction.

Consequences

• Quality numbers are measured, not guessed. The general rule behind them: texture hides what text exposes — a photograph tolerates quality 85 where a page of type does not, and that, not the pixel dimensions, is usually what decides the number.
• The crop is blind: there is no crop-and-zoom UI, so re-picking is the user’s only recourse. Keep the crop centred and predictable.
• Nothing upscales. A 300 px source is stored at 300 px, not blown up with invented pixels.