libvips/README.md

# libvips : an image processing library

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libvips is a [demand-driven, horizontally
threaded](https://github.com/libvips/libvips/wiki/Why-is-libvips-quick)
image processing library. Compared to similar
libraries, [libvips runs quickly and uses little
memory](https://github.com/libvips/libvips/wiki/Speed-and-memory-use).
libvips is licensed under the [LGPL
2.1+](https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html).

It has around [300
operations](http://libvips.github.io/libvips/API/current/func-list.html)
covering arithmetic, histograms, convolution, morphological
operations, frequency filtering, colour, resampling,
statistics and others. It supports a large range of [numeric
formats](http://libvips.github.io/libvips/API/current/VipsImage.html#VipsBandFormat),
from 8-bit int to 128-bit complex. Images can have any number of bands.
It supports a good range of image formats, including JPEG, TIFF, PNG, WebP,
FITS, Matlab, OpenEXR, PDF, SVG, HDR, PPM, CSV, GIF, Analyze, NIfTI, DeepZoom,
and OpenSlide.  It can also load images via ImageMagick or GraphicsMagick,
letting it load formats like DICOM.

It comes with bindings for
[C](http://libvips.github.io/libvips/API/current/using-from-c.html),
[C++](http://libvips.github.io/libvips/API/current/using-from-cpp.html),
and the
[command-line](http://libvips.github.io/libvips/API/current/using-cli.html).
Full bindings are available for [Ruby](https://rubygems.org/gems/ruby-vips),
[Python](https://pypi.python.org/pypi/pyvips),
[PHP](https://github.com/libvips/php-vips),
[.NET](https://www.nuget.org/packages/NetVips),
[Go](https://github.com/davidbyttow/govips), and
[Lua](https://github.com/libvips/lua-vips). libvips
is used as an image processing engine by [sharp
(on node.js)](https://www.npmjs.org/package/sharp),
[bimg](https://github.com/h2non/bimg), [sharp
for Go](https://github.com/DAddYE/vips), [Ruby on
Rails](http://edgeguides.rubyonrails.org/active_storage_overview.html),
[carrierwave-vips](https://github.com/eltiare/carrierwave-vips),
[mediawiki](http://www.mediawiki.org/wiki/Extension:VipsScaler),
[PhotoFlow](https://github.com/aferrero2707/PhotoFlow) and others.
The official libvips GUI is [nip2](https://github.com/libvips/nip2),
a strange combination of a spreadsheet and an photo editor.

There are packages for most unix-like operating systems and binaries for
Windows and OS X.

# Building libvips from a source tarball

We keep pre-baked tarballs of releases on the vips website:

https://github.com/libvips/libvips/releases

Untar, then in the libvips directory you should just be able to do:

    $ ./configure

Check the summary at the end of `configure` carefully.  libvips must have
`build-essential`, `pkg-config`, `glib2.0-dev`, `libexpat1-dev`.

You'll need the dev packages for the file format support you want. For basic
jpeg and tiff support, you'll need `libtiff5-dev`, `libjpeg-turbo8-dev`,
and `libgsf-1-dev`.  See the **Dependencies** section below for a full list
of the things that libvips can be configured to use.

Once `configure` is looking OK, compile and install with the usual:

    $ make
    $ sudo make install

By default this will install files to `/usr/local`.

We have detailed guides on the wiki for [building on
Windows](https://github.com/libvips/libvips/wiki/Build-for-Windows) and
[building on OS X](https://github.com/libvips/libvips/wiki/Build-for-macOS).

# Testing

Do a basic test of your build with:

    $ make check

Run the libvips test suite with:

    $ pytest

Run a specific test with:

    $ pytest test/test-suite/test_foreign.py -k test_tiff

You will need to install a variety of Python packages for this, including
pyvips, the libvips Python binding.

# Building libvips from git

Checkout the latest sources with:

    $ git clone git://github.com/libvips/libvips.git

Building from git needs more packages, you'll need at least `swig`, `gtk-doc` 
and `gobject-introspection`, see the dependencies section below. For example:

    $ brew install gtk-doc swig

Then build the build system with:

    $ ./autogen.sh

Debug build:

    $ CFLAGS="-g -Wall" CXXFLAGS="-g -Wall" \
        ./configure --prefix=/home/john/vips --enable-debug
    $ make
    $ make install

Leak check:

    $ export G_DEBUG=gc-friendly
    $ valgrind --suppressions=libvips.supp \
	       --leak-check=yes \
        vips ... > vips-vg.log 2>&1

Memory error debug:

    $ valgrind --vgdb=yes --vgdb-error=0 vips  ...

valgrind threading check:

    $ valgrind --tool=helgrind vips ... > vips-vg.log 2>&1

Clang build:

    $ CC=clang CXX=clang++ ./configure --prefix=/home/john/vips

Clang static analysis:

    $ scan-build ./configure --disable-introspection --disable-debug
    $ scan-build -o scan -v make 
    $ scan-view scan/2013-11-22-2

Clang dynamic analysis:

    $ FLAGS="-O1 -g -fsanitize=address"
    $ FLAGS="$FLAGS -fno-omit-frame-pointer -fno-optimize-sibling-calls"
    $ CC=clang CXX=clang++ LD=clang \
        CFLAGS="$FLAGS" CXXFLAGS="$FLAGS" LDFLAGS=-fsanitize=address \
        ./configure --prefix=/home/john/vips 

    $ FLAGS="-O1 -g -fsanitize=thread"
    $ FLAGS="$FLAGS -fPIC"
    $ FLAGS="$FLAGS -fno-omit-frame-pointer -fno-optimize-sibling-calls"
    $ CC=clang CXX=clang++ LD=clang \
      CFLAGS="$FLAGS" CXXFLAGS="$FLAGS" \
      LDFLAGS="-fsanitize=thread -fPIC" \
      ./configure --prefix=/home/john/vips \
        --without-magick \
        --disable-introspection
    $ G_DEBUG=gc-friendly vips copy ~/pics/k2.jpg x.jpg >& log

Build with the GCC auto-vectorizer and diagnostics (or just -O3):

    $ FLAGS="-O2 -march=native -ffast-math"
    $ FLAGS="$FLAGS -ftree-vectorize -fdump-tree-vect-details"
    $ CFLAGS="$FLAGS" CXXFLAGS="$FLAGS" \
      ./configure --prefix=/home/john/vips 

Static analysis with:

    $ cppcheck --force --enable=style . &> cppcheck.log

# Dependencies 

libvips has to have `glib2.0-dev`. Other dependencies are optional, see below.

# Optional dependencies

If suitable versions are found, libvips will add support for the following
libraries automatically. See `./configure --help` for a set of flags to
control library detection. Packages are generally found with `pkg-config`,
so make sure that is working.

libtiff, giflib and libjpeg do not usually use `pkg-config` so libvips looks for
them in the default path and in `$prefix`. If you have installed your own
versions of these libraries in a different location, libvips will not see
them. Use switches to libvips configure like:

    ./configure --prefix=/Users/john/vips \
        --with-giflib-includes=/opt/local/include \
        --with-giflib-libraries=/opt/local/lib \
        --with-tiff-includes=/opt/local/include \
        --with-tiff-libraries=/opt/local/lib \
        --with-jpeg-includes=/opt/local/include \
        --with-jpeg-libraries=/opt/local/lib

or perhaps:

    CFLAGS="-g -Wall -I/opt/local/include -L/opt/local/lib" \
    CXXFLAGS="-g -Wall -I/opt/local/include -L/opt/local/lib" \
    ./configure --prefix=/Users/john/vips 

to get libvips to see your builds.

### libjpeg

The IJG JPEG library. Use the `-turbo` version if you can. 

### libexif

If available, libvips adds support for EXIF metadata in JPEG files.

### giflib

The standard gif loader. If this is not present, vips will try to load gifs
via imagemagick instead.

### librsvg

The usual SVG loader. If this is not present, vips will try to load SVGs
via imagemagick instead.

### PDFium

If present, libvips will attempt to load PDFs via PDFium. This library must be
packaged by https://github.com/jcupitt/docker-builds/tree/master/pdfium

If PDFium is not detected, libvips will look for poppler-glib instead.

### libpoppler

The usual PDF loader. If this is not present, vips will try to load PDFs
via imagemagick.

### libgsf-1

If available, libvips adds support for creating image pyramids with `dzsave`. 

### libtiff

The TIFF library. It needs to be built with support for JPEG and
ZIP compression. 3.4b037 and later are known to be OK. 

### fftw3

If libvips finds this library, it uses it for fourier transforms. 

### lcms2, lcms

If present, `vips_icc_import()`, `vips_icc_export()` and `vips_icc_transform()`
are available for transforming images with ICC profiles. If `lcms2` is 
available it is used in preference to `lcms`, since it is faster.

### Large files

libvips uses the standard autoconf tests to work out how to support
large files (>2GB) on your system. Any reasonably recent unix should
be OK.

### libpng

If present, libvips can load and save png files. 

### libimagequant

If present, libvips can write 8-bit palette-ised PNGs.

### ImageMagick, or optionally GraphicsMagick

If available, libvips adds support for loading all libMagick-supported
image file types. Use `--with-magickpackage=GraphicsMagick` to build against 
graphicsmagick instead.

Imagemagick 6.9+ needs to have been built with `--with-modules`. Most packaged
IMs are, I think.

If you are going to be using libvips with untrusted images, perhaps in a
web-server, for example, you should consider the security implications of
using a package with such a large attack surface. You might prefer not to
enable Magick support. 

### pangoft2

If available, libvips adds support for text rendering. You need the
package pangoft2 in `pkg-config --list-all`.

### orc-0.4

If available, vips will accelerate some operations with this run-time
compiler.

### matio

If available, vips can load images from Matlab save files.

### cfitsio

If available, vips can load FITS images.

### libwebp

If available, vips can load and save WebP images.

### libniftiio

If available, vips can load and save NIFTI images.

### OpenEXR

If available, libvips will directly read (but not write, sadly)
OpenEXR images.

### OpenSlide

If available, libvips can load OpenSlide-supported virtual slide
files: Aperio, Hamamatsu, Leica, MIRAX, Sakura, Trestle, and Ventana.

# Disclaimer

No guarantees of performance accompany this software, nor is any
responsibility assumed on the part of the authors. Please read the licence
agreement.