Enhancement: Optional input file type extension to hint at best loader for Buffer/Stream

[inukshuk]

Question about an existing feature

Is it possible to pass a hint to libvips to know which loader to use?

What are you trying to achieve?

Using libvips (with libraw enabled) via Sharp to open RAW files. This works fine for most files I tested, but it fails for NEF files, which have a TIFF header. When opening a NEF file in Sharp I get a very small TIFF image (thumbnail?), not the full image.

When you searched for similar issues, what did you find that might be related?

I suspect this could be because of the TIFF header of NEF files. I think libvips tries to detect NEF files based on the filename, if sharp hands off a buffer or the already opened file maybe that's the reason why the file is then loaded as TIFF.

[lovell]

A possible future enhancement to expose control over this might be add a file extension hint as a constructor option that would use libvips file-based loader extension checking logic before falling back to checking the first few bytes.

As a possible workaround for now you can block the TIFF loader via:

sharp.block({ operation: ['VipsForeignLoadTiff'] })

https://sharp.pixelplumbing.com/api-utility/#block

Alternatively, if TIFF images are not required, compile libvips without libtiff.

[inukshuk]

Yes, exactly, I was wondering if there was a way to provide a hint via constructor options. But this is great: I missed the block/unblock API and it looks like this should work just fine -- blocking the TIFF loader when it's a NEF file and unblocking it again after processing. Thanks so much!

[inukshuk]

FYI, this didn't work in my case after all. But contrary to my statement above, passing the input as a filename does work. So the limitation is only when passing a buffer.

[lovell]

I've reopened as a future possible enhancement.