libvips 8.11 is now out, so here’s a quick overview of what’s new. Check the ChangeLog if you need more details.

Many thanks to Zeranoe, DarthSim, Projkt-James, afontenot, 781545872, erdmann, kleisauke and others for their great work on this release.

Lunaphore kindly sponsored the development of the new JPEG2000 features, see below.

Experimental JPEG-XL support

We’ve added experimental support for JPEG-XL. This is a new iteration of the JPEG standard, currently in development. The Chrome web browser supports it behind a flag and it looks like it might be enabled by default this autumn in Chrome 93.

There have been several attempts to replace JPEG with something better in the last few years. HEIC is perhaps the best known: it can compress files to about half the size of comparable JPEGs and supports a range of useful features like animations, transparency and lossless compression. Unfortunately, it has some patent issues which may limit its usefulness.

AVIF is rather like HEIC, but has no patents attached to it. Sadly the available load and save libraries are extremely slow.

JPEG-XL looks like it might avoid all these problems: it offers the same great compression and useful features as HEIC and AVIF, but has no problems with patents and is fast enough to be practical.

I made a sample image. You’ll need to zoom in to check details:

Compression and decompression is quite a bit quicker than HEIC:

$ time vips copy astronauts.png x.jxl
real 0m0.218s
user 0m0.291s
sys 0m0.204s

$ time vips copy astronauts.png x.heic
real 0m0.413s
user 0m1.273s
sys 0m0.048s 

The -all version of the Windows binaries include jxlload and jxlsave, but remember the API is likely to change in 8.12.

Thread recycling

We’ve revamped the libvips threading system. The new implementation uses a GLib thread pool to provide a single set of threads for the whole of libvips. This means threads get reused rather then being constantly created and destroyed.

This was originally intended for WebAssembly but it turned out to be useful for native environments as well. Relative speed-ups are varying between ~4% and ~15% compared to the previous implementation. Especially for short-lived pipelines and long-running processes, a performance improvement can be observed.

Loadable modules for some dependencies

libvips now supports building OpenSlide, libheif, Poppler and libMagick as dynamically loadable modules. This makes it easier for distributions to provide separate (optional) packages for these dependencies, making the core package much slimmer and thus reducing the attack surface. Distributing separate packages could also help to comply with GPL licensing (“mere aggregation” clause) or patent-encumbered software.

GModule is used to accomplish this in a portable way. We already had a simple plugin system based on this, but the build part was not yet implemented.

These loadable modules are built automatically when GModule is supported, which should be at least Linux, Windows and macOS. It can be disabled by passing --disable-modules while configuring libvips.

Full-colour text rendering

The libvips text operator was designed a while ago, when fonts were still black and white. It outputs a one-band mask image which you then process with the other libvips operations to do things like rendering text on an image.

Many fonts, especially emoji fonts, now have full-colour SVG characters. There’s a new rgba flag to text to enable colour rendering. For example:

$ vips text x.png "😀<span foreground='red'>red</span><span background='cyan'>blue</span>" --dpi 300 --rgba

Makes this:

You can then use composite to render these text RGBA images on to another image.

JPEG2000 support

Thanks to generous sponsorship from Lunaphore, we’ve added support for the (now rather elderly) JPEG2000 format.

The jp2kload and jp2ksave operations support all the file format features: shrink-on-load, 8-, 16- and 32-bit data, any number of image bands, tiled images, YCC colourspace, lossless compression, and optional chroma subsampling. The lossy compression profile (controlled by a Q parameter) is derived from the British Museum’s JPEG2000 recommendations.

We’ve also added support for JPEG2000 as a codec for TIFF load and save. This means you can now directly load and save some popular slide image formats. This should be useful for people in the medical imaging community.

It’s easy to use – for example:

$ vips copy k2.jpg x.tif[compression=jp2k,Q=90,tile]
$ vips copy k2.jpg x.tif[compression=jp2k,lossless,tile]

C++ API improments

We’ve spent some time improving the C++ API.

We now use doxygen to generate C++ API docs automatically, and we’ve written a set of API comments. Hopefully the new documentation should be a big improvement.

There are a couple of functional improvements too. There’s support for VipsInterpolate, guint64 and a new constructor, VImage::new_from_memory_steal, which can save a copy operation.

Minor improvements

• The perlin, worley and gaussnoise operators have a new seed parameter to set the seed for their random number generator.

• The rank operator has a new path for large windows on 8-bit images. It can be up to 20 times faster in some cases.

• Image histograms on large images now use double values. Previously, we were limited to images with under 2^32 pixels.

• There’s a new black_point_compensation option for colour operations involving ICC profiles, and detection of bad profiles and fallback to default profiles is much better.

• The loaders and savers for PDFium, OpenSlide, vips, NIfTI, and FITS have been moved to the new libvips IO framework.

• vipsthumbnail can now load and save to and from stdin and stdout.

• PNG save selects between 8- and 16-bit output more intelligently, and supports background colour as metadata.

• We’ve switched GIF load to the excellent libnsgif library, and libvips embeds the library code.

• tiffsave can write premultipled alpha.

• PDFium support has been revised. It should now build very simply, and ought to be much faster in threaded applications.

• We’ve fixed a range of reference leaks in the mosaicing package, and we now run the leak checker as part of CI.

As usual, the ChangeLog has more details, if you’re interested.