Feature Request: Save Progressive jpeg

[nla-brandonjames]

Description

I can't find an API in ImageSharp to save my images in the progressive jpeg format. It is a requirement for my application. I am capable of saving as a baseline image.

• ImageSharp version: 1.0.0-beta2
• Other ImageSharp packages and versions:
• Environment (Operating system, version and so on): Windows 10 (dev) Ubuntu 16.04 (prod)
• .NET Framework version: .NET Core 2.0.5

[JimBobSquarePants]

@nla-brandonjames

Unfortunately we don't have support for saving progressive jpegs. See #10 It's something I REALLY want though.

We'd need support from someone in the community if we are in any way likely to get it for v1.0 as jpeg is.... complicated. At the moment you would have to post process the images using something like mozjpeg.

Cheers

James

P.S In the future could you please ask questions in the Gitter channel? We're trying to keep the issue tracker clear so we can stay on top of things.

[nla-brandonjames]

@JimBobSquarePants Okay, will do. I have a couple more things to add to this.

[JimBobSquarePants]

Thanks! 👍

[maartenmensink]

Is this still on the roadmap?

[JimBobSquarePants]

If someone wants to implement it yes.

[maartenmensink]

We are willing to help with the implementation for sure. My first gut feeling is that we would expand the current JpegEncoder with a property Progressive which should default to false.

Jpeg Progressive Encoder

• Second we need to port a good working progressive encoder like libjpeg-turbo if that is offcourse allowed with respect to their license
• Create one from scratch.

What are your considerations in regards to this?

[antonfirsov]

port a good working progressive encoder like libjpeg-turbo

Note that libjpeg-turbo has it's own memory management primitives, a bunch of C indirections, and the optimized SIMD methods are implemented in assembly, which makes it extremely hard to port it in an efficient manner. There is a naive port of classic LibJpeg under https://github.com/BitMiracle/libjpeg.net/tree/master/LibJpeg/Classic/Internal. Such a port will leave you in a place where both the performance and the code quality is quite bad, and a huge amount of additional work has to be spent to bring it to an acceptable level.

Unless someone is really experienced with porting native code including the SIMD bits, I would prefer extending our current encoder with the bits needed for saving progressive jpegs. Significant amount of performance work has been spent on it already, including SIMD optimization of color codecs (#1508), I think it would be more beneficial to build on top of that work than to start over from scratch.

new JpegEncoder { Progressive = true }

One should be also able to set the number of scans.

[JimBobSquarePants]

We are willing to help with the implementation for sure.
@maartenmensink wonderful, thank you! ❤️

Unless someone is really experienced with porting native code including the SIMD bits, I would prefer extending our current encoder

Yep agreed, this is the sanest approach. Following #1632 that should be much easier to do.