How would I pass loader options to VImage.thumbnailSource?

[jebbench]

I'm building an image proxy server to thumbnail and convert PDFs.

If the user specifies that they want a thumbnail I'm using the VImage.thumbnailSource method to create a VImage otherwise I use VImage.newFromSource.

They can also specify what page of the PDF they would like to load; when they do so I need to pass the page=x option to the loader.

I would like to be able to do something like:

var loadArgs = emptyArray<VipsOption>()
loadArgs += VipsOption.Enum("access", VipsAccess.ACCESS_SEQUENTIAL)
params["page"]?.let {
    val page = it.toInt() - 1
    LOGGER.trace { "Loading page '$page'..." }
    loadArgs += VipsOption.Int("page", page)
}

val image = if(thumbnail){
    VImage.thumbnailSource(
        arena,
        vSource,
        targetWidth,
        VipsOption.Int("height", targetHeight),
        VipsOption.String("option-string", loadArgs.joinToString(",") { "${it.key()}=${it.value()}" }) // Or something
    )
} else {
    VImage.newFromSource(arena, vSource, *loadArgs)
}

My question is: is there an existing utility to convert an array of VipsOption to a string suitable for passing as the loader "option-string"? Or is there a better way to do this?

Cheers,
JB

[lopcode]

There's nothing like that in the vips-ffm API that I can remember. I feel like there must be a way to pass arguments like that in libvips itself - if you can figure that out, I can figure out what's missing in these bindings.

I'm planning to get the two open PRs reviewed, tweaked, and merged in, then have a think about this after, but it might be a couple of weeks - in the mean time, you could have a look at libvips to figure out what might be missing here (even if it's just docs).