binding for the libvips image processing library, API mode
This module wraps the libvips image processing library.
If you have the development headers for libvips installed and have a working C compiler, this module will use cffi API mode to try to build a libvips binary extension for your Python.
If it is unable to build a binary extension, it will use cffi ABI mode instead and only needs the libvips shared library. This takes longer to start up and is typically ~20% slower in execution. You can find out how pyvips installed with pip show pyvips.
This binding passes the vips test suite cleanly and with no leaks under python2.7 - python3.6, pypy and pypy3 on Windows, macOS and Linux.
We have formatted docs online here:
How it works
Programs that use pyvips don’t manipulate images directly, instead they create pipelines of image processing operations building on a source image. When the end of the pipe is connected to a destination, the whole pipeline executes at once, streaming the image in parallel from source to destination a section at a time.
Because pyvips is parallel, it’s quick, and because it doesn’t need to keep entire images in memory, it’s light. For example, the libvips speed and memory use benchmark:
Loads a large tiff image, shrinks by 10%, sharpens, and saves again. On this test pyvips is typically 3x faster than ImageMagick and needs 5x less memory.
There’s a handy chapter in the docs explaining how libvips opens files, which gives some more background.
You need the libvips shared library on your library search path, version 8.2 or later. On Linux and macOS, you can just install via your package manager; on Windows you can download a pre-compiled binary from the libvips website.
Next, install this package, perhaps:
$ pip install --user pyvips
On Windows, you’ll need a 64-bit Python. The official one works well. Anaconda probably won’t work without some effort – they have their own packaging system.
Extra notes for Windows
On Windows, you will need to add vips-dev-x.ybin to your PATH so that pyvips can find all the DLLs it needs. You can either do this in the Advanced System Settings control panel, or you can just change PATH for your pyvips program.
If you set the PATH environment variable in the control panel, you can use the vips command-line tools, which I find useful. However, this will add a lot of extra DLLs to your search path and they might conflict with other programs, so it’s usually safer just to set PATH in your program.
To set PATH from within Python, you need something like this at the start of your program:
import os vipshome = 'c:\\vips-dev-8.7\\bin' os.environ['PATH'] = vipshome + ';' + os.environ['PATH']
Now when you import pyvips, it should be able to find the DLLs.
Test your install
Try this test program:
import logging; logging.basicConfig(level = logging.DEBUG) import pyvips
If pyvips was able to build and use a binary module on your computer (API mode) you should see:
$ ./pyv.py DEBUG:pyvips:Loaded binary module _libvips DEBUG:pyvips:Inited libvips
If the build failed (fallback to ABI mode), or there was a header or version mismatch, you might see:
$ ./pyv.py DEBUG:pyvips:Loaded binary module _libvips DEBUG:pyvips:Binary module load failed: not all arguments converted during string formatting DEBUG:pyvips:Falling back to ABI mode DEBUG:pyvips:Loaded lib <cffi.api.FFILibrary_libvips.so.42 object at 0x7f29fa015190> DEBUG:pyvips:Loaded lib <cffi.api.FFILibrary_libgobject-2.0.so.0 object at 0x7f29fa015110> DEBUG:pyvips:Inited libvips
pyvips will work fine in this fallback mode, it’s just a bit slower.
If API mode stops working, you can fix it by reinstalling pyvips. You should make sure pip is not reusing a cached wheel, e.g. by using pip install --no-cache-dir pyvips.
This sample program loads a JPG image, doubles the value of every green pixel, sharpens, and then writes the image back to the filesystem again:
import pyvips image = pyvips.Image.new_from_file('some-image.jpg', access='sequential') image *= [1, 2, 1] mask = pyvips.Image.new_from_array([[-1, -1, -1], [-1, 16, -1], [-1, -1, -1] ], scale=8) image = image.conv(mask, precision='integer') image.write_to_file('x.jpg')
Converting old code
To convert old code, replace the lines:
import gi gi.require_version('Vips', '8.0') from gi.repository import Vips
import pyvips Vips = pyvips
Instead of the pyvips = Vips, you can of course also swap all Vips for pyvips with eg.:
The Python binding included in libvips works, but porting and installation are more difficult than they should be.
This new binding is:
- compatible with the current Python binding (it runs the same test suite, unmodified)
- easier to install, since the stack is much smaller, and there are no issues with the overrides directory
- faster, since we implement Buffer and save some copies
- faster, since it is “thinner”. The ffi Ruby binding is about twice as fast as the gobject-introspection one, when running the test suite
- portable across CPython, PyPy and others
- more simply portable to Windows
- easy to package for pip
Local user install:
$ pip install --user -e . $ pip3 install --user -e . $ pypy -m pip --user -e .
Run all tests:
Run test suite:
$ tox test
Run a specific test:
$ pytest tests/test_conversion.py
$ tox qa
Generate HTML docs in doc/build/html:
$ cd doc; sphinx-build -bhtml . build/html
$ cd doc; \ python -c "import pyvips; pyvips.Operation.generate_sphinx_all()" > x
And copy-paste x into the obvious place in doc/vimage.rst.
Update version number:
$ vi pyvips/version.py $ vi doc/conf.py
Update pypi package:
$ python setup.py sdist $ twine upload dist/*
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