libvips 8.7 is finally done!

This post summarizes what’s new – check the ChangeLog if you need more details.

New operators

libvips has a pair of new edge detectors. vips_sobel() is very simple and is just a useful convenience, but vips_canny() is rather fancy.

vips_canny() just does the streaming part of the Canny algorithm. Thresholding and connectivity are up to you.

vips_transpose3d() is useful for volumetric images. libvips loads volumes as a single very tall, thin image with all the image slices one above the other. This new operation swaps the outer two dimensions, so output page N is made from all the Nth scanlines in the input pages.

Finally, vips_rotate() is a convenience operation that just calls vips_similarity() for you. It’s supposed to be easier to find in the API.

Improvements to existing operators

Thanks for work by fangqiao, vips_text() has a new parameter fontfile. This lets you specify a font to render text with, without having to install the font on your system.

medakk has added x and y parameters to vips_composite(), so you can now position layers relative to each other.

The Hough transform operators have been revised. vips_hough_line() is 4x faster, and vips_hough_circle() is 2x faster.

There’s now a Mitchell interpolation kernel you can use for image resizing.

New format support

Work by dlemstra has resulted in vips_magicksave(). This new operation can write an image via libMagick in any format that libMagick supports. It’s still missing some features like ICC profile support, but it works well for things like animated GIF write.

There’s a new, optional PDF loader based on Google’s PDFium project. libvips has had a PDF loader based on poppler-glib for a while, but the poppler GPL licence is unsuitable for some projects. This new PDFium loader should be more widely useful.

libvips now has support for NIfTI load and save. This is a popular format for brain imaging.

Improvements to file format support

felixbuenemann has added support for 8-bit palette PNG images. These can be quite a bit smaller for some sorts of image. New parameters for vips_pngsave() let you control the dithering, number of colours, and quantisation quality.

harukizaemon has added a system to the pyramid builders in vips_dzsave() and vips_tiffsave() to let you specify a x2 shrink operation. As well as mean, (the previous system) you can now also specify mode and median. These are useful for pyramiding large label sets.

The JPEG loader has better metadata support. It will now tell you about the type of source image chroma subsampling, supports modification of string-valued EXIF tags, supports removal of the embedded thumbnail, and has a better system for reporting interlaced image sources.

The PDF loader has better support for PDFs with a transparent background, reports the number of pages in a document, and lets you use PDFium instead of poppler (see above).

Infrastructure improvements

New(-ish) test suite

The libvips test suite was inside the separate pyvips project. We’ve moved it inside libvips and it’s now run automatically on every commit, and by make check.

Hopefully this will make it easier to catch errors.

Breaking changes

Actually using vips_hough_line() in a project revealed a flaw in the way that it encoded the parameter space. We’ve had to change this, but hopefully not too much code will break.

The create functions like vips_black() used to set their interpretation to b-w or multiband depending on whether they were outputting a single or a multiband image. This caused quite a bit of confusion, so they now always set multiband, even when outputting single band images. The rules for alpha channels have been revised to match.

vips7 is now off by default

We launched the new vips8 API back in 2015. Now with 8.7, we’re making vips7 off by default.

For C, you’ll need to add #include <vips7compat.h> to your program to get the old API.

The vips7 C++ API is not built or installed by default. You’ll need to give configure the --enable-cpp7 flag.

The vips7 Python interface is not built or installed by default. You’ll need to give configure the --enable-pyvips7 flag.

The vips8 Python interface that came with libvips is also off by default. You’ll need to give configure the --enable-pyvips8 flag. But you should use pyvips instead: it’s 100% compatible and can be installed with a simple pip install pyvips.

Plus many even smaller bug fixes and improvements. As usual, the ChangeLog has more details, if you’re interested.