libjpeg vs. libjpeg-turbo

[Rainer Müller]

On 2015-05-20 12:49, René J.V. Bertin wrote:
> On Wednesday May 20 2015 12:11:08 Clemens Lang wrote:
> 
> How do libjpeg-turbo and mozjpeg compare except in the latter's
> features to create slightly smaller files (at what computing cost)?

http://www.libjpeg-turbo.org/About/Mozjpeg

In short: mozjpeg produces smaller files by using progressive JPEG
encoding, but it is significantly slower. Note this only applies to
encoding, the images are compatible with any JPEG decoder.

> That would still require all ports to use this kind of dependency. If
> both alternatives are really interchangeable, I'd rather see them as
> variants of a master port, e.g. port:jpeg with +turbo being the
> default variant and +moz (or +mozjpeg) being an alternative variant.
> That would provide users with choice without imposing an unnecessary
> change on port maintainers. With (at least) Debian and Ubuntu this is
> handled by the jpeg-turbo packages indicating that they replace (are
> alternatives to) the standard libjpeg versions; sadly MacPorts
> doesn't have a similar feature. I've already raised this idea a while
> ago, but cannot remember how it was received...

Variants are not useful for completely different software projects with
distinct releases and versioning schema. What would you use in the port
version?

Yes, having virtual "provides" dependencies would solve this. But we
don't have that and we are currently using the path: style dependencies
to achieve something similar. Discussions about adding such features
should take place on macports-dev.

Rainer