Add support for progressive JPEGs

[jadsonlourenco]

Good feature to have, did you think to support it?

[willnorris]

Do you know of libraries that have support for it? I see no mention in https://golang.org/pkg/image/jpeg/.

[willnorris]

Looks like decoding progressive jpegs is supported, but no mention of encoding.

[willnorris]

And this post from Nigel doesn't sound encouraging.

Nothing is planned.

IIRC, if you want to tackle this yourself, note that there are two
dimensions (S and A) to progressivity. For decoding, look near the
"spec calls these values Ss, Se, Ah and Al" comment in scan.go.

so the biggest blocker for this would be a Go library that has support for it. I really don't want to link in any C libraries like imagemagick or whatever, so we'd need a Go solution.

[jadsonlourenco]

Ok, thank you for the answer, closing.

[willnorris]

To be clear, I don't think this needs to be closed. I think it's a fine feature request, it's just one that we likely wouldn't be able to add for a while since it's gated on a jpeg library that supports it. But I wouldn't want to lose track of the request.

[schmunk42]

Any updates on this? Would be really cool to have it.