JPEG compression

[boan-jfm]

I am trying to optimize the compression to match a library called "jpeg-archive": https://github.com/danielgtaylor/jpeg-archive - one of the goals is to minimize storage and bandwidth usage when serving images over the web.

I am using the jpegsave and have tried to adjust the following options:

        // default settings
        $options = [
            'Q'                   => 75,
            'optimize_coding'     => true,
            'interlace'           => false,
            'strip'               => true, // Metadata
            'quant-table'         => 0,
            'overshoot-deringing' => false,
            'trellis-quant'       => false,
        ];

But I get some warnings when using settings other than the default:

            'quant-table'         => 1,
            'overshoot-deringing' => true,
            'trellis-quant'       => true,

(process:15582): VIPS-WARNING **: 12:42:20.675: ignoring trellis_quant

(process:15582): VIPS-WARNING **: 12:42:20.675: ignoring overshoot_deringing

(process:15582): VIPS-WARNING **: 12:42:20.675: ignoring quant_table

[jcupitt]

Hello again,

Those options are for mozjpeg:

https://github.com/mozilla/mozjpeg

It's mozilla's libjpeg fork with a range of compression improvements. It can make JPEGs roughly 30% smaller without breaking compatibility. It does tend to be a lot slower, though I think that has improved recently.

To use it from libvips, you need to build everything against mozjpeg rather than jpeg-turbo (the usual one). This usually involves building the entire libvips binary from scratch, unfortunately, though it depends what formats you want to support.

There's a sample dockerfile for libvips with mozjpeg on ubuntu 20.04 here:

https://github.com/jcupitt/docker-builds/tree/master/libvips-mozjpeg-ubuntu20.04