LoadImageFromFile should use native libvips implementation

[ugljesas]

This is more of a feature request - but I think there are multiple use-cases where it would be beneficial to use the native libvips implementation for loading from a file. The current implementation reads the whole file into memory and calls LoadImageFromBuffer.

In our case, we are using govips as part of the detect pipeline for uploaded user media which could be one of multiple types. Natively, libvips only reads the file header to return the metadata. In the case of a large file (e.g. video of 600MB), and a cloud environment where disk throughput is suboptimal (capped at 200MB/s) it can take a substantial amount of time to fetch the file meta (or determine that the file is not supported). We reverted to calling the vipsheader CLI here to save time.

Also, loading the whole file into memory seems unnecessary as libvips has optimizations to not load the whole file at once where possible in order to be more RAM efficient.

[tonimelisma]

Hey @ugljesas thanks for the comment. I feel like that would require a complete refactoring of the govips library, the data structures and how we use libvips. As usual, this is an open source project which is mostly maintained by a few eager volunteers in their spare time, so I don't think we have capacity for something like that. If we'd start all over, I'm sure we might consider an approach like that, besides using glib introspection for automatic API generation and a bunch of other things.

Do you think you'd personally have bandwidth to plan and/or implement parts of such a change?

[ugljesas]

Hi @tonimelisma, thank you for your reply. I'm fairly new to Golang and haven't had much hands-on experience with c-bindings yet. That said, looking into the code I had the impression it could be done without a bigger refactor, in line with the pull request @cshum made here (thank you!!). Of course, due to my lack of experience with this, I'm not aware of all the implications of the change. Could you please elaborate on why you feel like this would require a complete refactoring of govips? I'd be open to helping develop and/or test this in some capacity but would probably need some guidance.

[tonimelisma]

Perhaps you're right, it could be I didn't look into it deep enough. Unfortunately I've just moved to the US and don't have much capacity to dig deeper into this the coming days.