Widens the preview-only fallback. A recognised raw whose decode fails now falls back
to its embedded JPEG for any decode error (unsupported, corrupt, limit, TIFF
structure), not only an unsupported variant, and the preview search covers more
containers:
- Canon CRW, Minolta MRW and Sigma X3F are recognised by their magic (RawFormat
Crw, Mrw, X3f) instead of failing as "RawOther files are not supported yet".
- A TIFF whose IFD0 has no ImageWidth/ImageLength but a JPEG pointer or SubIFDs
(Kodak KDC) is a raw container, not a malformed image. TIFF compression 99
(Leaf MOS) counts as a raw compression.
- When no tag points to a preview, a recognised raw we cannot decode is scanned
for the largest complete three-component DCT JPEG. A preview whose first byte
was overwritten (Minolta, Epson) is restored. A one-component JPEG is skipped
(a PowerShot CRW stores its mosaic that way).
Files with no JPEG at all still fail with "without an embedded preview".