Having difficulties using Mozjpeg for JPEG encoding optimizations

[quentin-bettoum]

I was looking at the options set in this function

  # From: https://www.libvips.org/API/current/VipsForeignSave.html#vips-jpegsave
  # Applies only to jpeg save
  # For maximum compression with mozjpeg, a useful set of options is
  # strip, optimize-coding, interlace, optimize-scans, trellis-quant, quant_table=3.
  defp validate_option({:minimize_file_size, true}, options, image_type) when is_jpg(image_type) do
    options =
      options
      |> Keyword.delete(:minimize_file_size)
      |> Keyword.put(:strip, true)
      |> Keyword.put(:"optimize-coding", true)
      |> Keyword.put(:interlace, true)
      |> Keyword.put(:"optimize-scans", true)
      |> Keyword.put(:"trellis-quant", true)
      |> Keyword.put(:quant_table, 3)

    {:cont, options}
  end

As stated, some of these options (trellis-quant, optimize-scans, quant-table) would only work with mozjpeg.
As I wanted to see the differences these options would make, I tried to set up mozjpeg.
At first, I thought it would be a matter of installing it on my system, my package manager even asked me if I wanted to replace libjpeg-turbo by the new mozjpeg library as both of these packages were in conflict. But even after installing it, the parameters mentioned above were still outputing these warnings

VIPS-WARNING **: 00:20:25.349: ignoring trellis_quant
VIPS-WARNING **: 00:20:25.349: ignoring optimize_scans
VIPS-WARNING **: 00:20:25.349: ignoring quant_table

I also tried using the precompiled libvips from Vix by removing the VIX_COMPILATION_MODE PLATFORM_PROVIDED_LIBVIPS env variable and rebuilding the deps, but it still outputs the same warnings.

The strange thing is, when I install mozjpeg, there are differences when I try to encode jpeg image. They definitely have a different output weight and compression, but the parameters are still ignored, so I'm not sure what's happening.

Any help would be appreciated.

[kipcole9]

Not an area I've dived into @quentin-bettoum so I can only suggest two things:

1. Same issue if using the vips command line? If so, sounds like a vips build issue.
2. I invoke the name of someone who understands this much better than I ever will. Calling @akash-akya to see if he has some ideas or suggestions.

[quentin-bettoum]

Yes, I have this issue with the CLI too.
Actually I didn't remove the VIX_COMPILATION_MODE properly, so it was not using the sharp binary. Now it seems to work if I use Vix or Image.

Maybe libvips need to be built with some option to be used with mozjpeg.

Those 2 lines definitely outputs a different image.

Image.open!("images/forest.jpg") |> Vix.Vips.Image.write_to_file("images/forestoptim.jpg[Q=30,strip,interlace,optimize-coding,optimize-scans,trellis-quant,quant-table=3]")
Image.open!("images/forest.jpg") |> Vix.Vips.Image.write_to_file("images/forestnooptim.jpg[Q=30,strip,interlace,optimize-coding]")

In CLI, with mojzpeg installed, those two commands produce almost a byte-size identical output of the first line in Vix (the line using the mozjpeg optims with the forestoptim.jpg output).
Except the second one will write warnings saying it's ignoring the trellis_quant, optimize_scans and quant_table parameters.
So it's ignoring these parameters but it's producing identical outputs to Vix using the same parameters.

# With mozjpeg installed
vips copy forest.jpg cli1.jpg[Q=30,strip,interlace,optimize-coding]
vips copy forest.jpg cli2.jpg[Q=30,strip,interlace,optimize-coding,optimize-scans,trellis-quant,quant-table=3]

[kipcole9]

Maybe libvips need to be built with some option to be used with mozjpeg

Very possible. I'd suggest clarify that in the libvips discussion area since this is outside the scope of Image (and well beyond my knowledge).

[akash-akya]

Hi @quentin-bettoum, I checked the commands you shared and it's working for me. Btw I just installed vips from brew, and it uses mozjpeg by default

$ vips copy forest.jpg cli2.jpg[Q=30,strip,interlace,optimize-coding,optimize-scans,trellis-quant,quant-table=3]

$vips copy forest.jpg cli.jpg

Which os are you using? we can check and confirm if it is really using mozjpeg using the linker tooling os provides.
On macos I can check this with otool.

$ otool -L $(which vips) | grep libvips
	/usr/local/Cellar/vips/8.13.3_1/lib/libvips.42.dylib (compatibility version 58.0.0, current version 58.3.0)

$ otool -L /usr/local/Cellar/vips/*/lib/libvips.42.dylib | grep jpeg
	/usr/local/opt/mozjpeg/lib/libjpeg.62.dylib (compatibility version 62.0.0, current version 62.3.0)
	/usr/local/opt/openjpeg/lib/libopenjp2.7.dylib (compatibility version 7.0.0, current version 2.5.0)

On Linux you can use lld I think.

[quentin-bettoum]

Thanks for replying,

Here is what I managed to get:

$ ldd $(which vips) | grep libvips
	libvips.so.42 => /usr/lib/libvips.so.42 (0x00007f4054400000)

$ ldd /usr/lib/libvips.so.42 | grep jpeg
	libjpeg.so.8 => /usr/lib/libjpeg.so.8 (0x00007f82bbb3f000)

I am on Linux (arch) and I use these versions:
vips-8.14.1 which come from the official Arch repository. They are using this PKGBUILD.
mozjpeg 4.1.1-2 from the Arch User Repository which is using this PKGBUILD.

Maybe it is built differently than on homebrew?

[akash-akya]

as you can see it's not using mozjpeg.
Can you try this?

• Uninstall libvips
• Install mozjpeg
• Install libvips

Please share the linker output as well

[quentin-bettoum]

I tried this, but the output is still pretty much the same

$ ldd $(which vips) | grep libvips
	libvips.so.42 => /usr/lib/libvips.so.42 (0x00007f5cfaa00000)
$ ldd /usr/lib/libvips.so.42 | grep jpeg
	libjpeg.so.8 => /usr/lib/libjpeg.so.8 (0x00007f161c13f000)

I also opened a discussion here on the libvips repo
The answer of jcupitt suggests that in order to use libvips with mozjpeg, a custom build of libvips must be done.

I'm guessing my distro build of libvips doesn't include mozjpeg by default so that's why it's not working.
I might try to tweak the PKGBUILD to see if I can make it work, and eventually make a pull request.
I could try to take inspiration from the homebrew formula or from the Sharp build procedure if I ever find it.

At least I can still use the prebuilt binary included with Vix.

In any case, thanks for your help.

[akash-akya]

If you have some time to get into nix, you could try the approach i mentioned on that thread :)
libvips/libvips#3360 (comment)

I think this is better than going with docker route.

[quentin-bettoum]

Thanks for taking the time to try this.

I will definitely consider trying Nix.