Exif metadata cannot be read out for .tiff files

[PatrickHallek]

What are you trying todo?

I want to use the exif metadata API in order to create and read out additional metadata from a TIFF file.

What are the steps to reproduce?

await sharp({ create: { width: 1000, height: 48, channels: 3, background: '#fff' } })
        .withMetadata({ exif: { IFD0: { Copyright: 'Some Name' } } })
        .toFile('sweep.tiff')

const tiff = await sharp('sweep.tiff').metadata()
console.log(tiff.exif) // logs undefined

What is the expected behaviour?

Should log { IFD0: { Copyright: 'Some Name' } } (or a Buffer)

What is the output of running npx envinfo --binaries --system?

 System:
    OS: macOS 12.1
    CPU: (8) x64 Intel(R) Core(TM) i5-1038NG7 CPU @ 2.00GHz
    Memory: 20.61 MB / 16.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.13.0 - ~/.nvm/versions/node/v16.13.0/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 8.4.0 - ~/.nvm/versions/node/v16.13.0/bin/npm

[lovell]

Hi, libvips doesn't currently support writing (or reading) EXIF metadata with TIFF files. My understanding is that it's somewhat more complicated than supporting EXIF in other formats as TIFF uses slightly different field names (despite EXIF as a standard originating from TIFF).

We should probably update the sharp documentation to reflect this.

[lovell]

I've added a note to the docs about this via commit 4c29368 - closing as I'm not sure there's much else we can do, as this is not a simple task in either sharp or libvips.