Edit (2023-04-05): Added some suggestions by the author/developer of libvips.
Today I discovered libvips, a command line utility and library to manipulate and process images, and I am impressed. I’ve been using ImageMagick and its fork, GraphicsMagick, for as long as I have had to process images from the CLI, and they work well for moderately-sized images. But lately, I have been preparing virtual texture datasets for Gaia Sky and the sizes of my images have increased exponentially. Right now I’m processing 64K and 128K images on the regular (that is 131072x65536 pixels), and ImageMagick just can’t do it reliably. It uses so much memory that it can’t even split a 64K image in a 32 GB RAM machine without running out of it. Running it with the suggested options to limit memory usage (
--limit memory xx mb, etc.) and use a disk cache never works for me. It just produces blank images for some reason. So after implementing a couple of Python scripts based on OpenCV and NumPy to do some basic cropping, I took on the task of finding a proper, capable replacement. And found it I did. Libvips is the perfect tool, it seems. Based on my few first tests, it performs much better than ImageMagick and GraphicsMagick. It is super fast and never seems to use much memory, no matter how big an image I throw at it.
Here are a few handy commands to do some basic tasks with the command line tool.
resize operation to scale images up and down:
# Resize the INPUT image using the double scale value and save it to OUTPUT vips resize INPUT OUTPUT scale
However, resizing using the
thumbnail operation can be quicker, as it uses shrink-on-load tricks:
# Resize the INPUT image to the given WIDTH, aspect ratio is kept vips thumbnail INPUT OUTPUT WIDTH
Converting formats is easy with the
# Simple format conversion vips copy image.png image.jpg # Attributes can be added to load and save operations vips copy image.png image.jpg[Q=85]
You can also use the dedicated save operations for each format:
# Convert to JPEG XL vips jxlsave image.jpg image.jxl # Convert to PNG vips pngsave image.jpg image.png # Convert to JPEG vips jpegsave image.png image.jpg # Convert to TIFF vips tiffsave image.jpg image.tiff # Convert to WebP vips webpsave image.jpg image.webp # Convert to GIF vips gifsave image.jpg image.gif # Convert to FITS vips fitssave image.jpg image.fits
Extract an area (crop):
# Crop an area of width x height starting at pixel [left, top] vips crop INPUT OUTPUT left top width height
In general, you can discover all the subcommands by doing:
This outputs a list of all subcommands, which you can parse. Then, just do
vips command to get help as to how to use a particular command.
The official documentation for the libvips command line interface is here.