libvips/README.md

# libvips : an image processing library

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# Introduction

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](https://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
types](https://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, JPEG2000, JPEG-XL,
TIFF, PNG, WebP, HEIC, AVIF, FITS, Matlab, OpenEXR, PDF, SVG, HDR, PPM / PGM /
PFM, CSV, GIF, Analyze, NIfTI, DeepZoom, and OpenSlide. It can also load
images via ImageMagick or GraphicsMagick, letting it work with formats
like DICOM.

It comes with bindings for
[C](https://libvips.github.io/libvips/API/current/using-from-c.html),
[C++](https://libvips.github.io/libvips/API/current/using-from-cpp.html),
and the
[command-line](https://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),
[C# / .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](https://edgeguides.rubyonrails.org/active_storage_overview.html),
[carrierwave-vips](https://github.com/eltiare/carrierwave-vips),
[mediawiki](https://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 a photo editor.

# Install

There are packages for most Unix-like operating systems, including
macOS. Check your package manager.

There are binaries for Windows in
[releases](https://github.com/libvips/libvips/releases).

The [libvips website](https://libvips.github.io/libvips) has [detailed
install notes](https://libvips.github.io/libvips/install.html).

# Building from source

libvips uses the [Meson build system](https://mesonbuild.com), version 0.56 or
later. The build system also needs `ninja`. 

To compile, libvips must have `build-essential`, `pkg-config`,
`libglib2.0-dev`, `libexpat1-dev`.  See the **Dependencies** section below
for a full list of the libvips optional dependencies.

## Cheatsheet 

```
cd libvips-x.y.x
meson setup build --prefix=/aaa/bbb/ccc
cd build
ninja
ninja install
```

Notes:

- Check the output of `meson setup` carefully and make sure it found
  everything you wanted it to find.
- Use flags like `-Dnsgif=false` to turn options on and off, see
  `meson_options.txt` for a list of all the options libvips supports.
- Use `--buildtype=release` for a release build.
- You might need `--libdir=lib` on Debian if you don't want the arch name in
  the library.
- Use `--default-library=static` for a static build.
- Use `ninja test` to run the tests.
- There's a more comprehensive test suite you can run with `pytest`.

## Optional dependencies

If suitable versions are found, libvips will add support for the following
libraries automatically. Packages are generally found with `pkg-config`,
so make sure that is working.

### libjpeg

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

### libexif

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

### 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 with PDFium. Download the 
prebuilt pdfium binary from: 

    https://github.com/bblanchon/pdfium-binaries

Untar to the libvips install prefix, for example:

    cd ~/vips
    tar xf ~/pdfium-linux.tgz

Create a `pdfium.pc` like this (update the version number):

    VIPSHOME=/home/john/vips
    cat > $VIPSHOME/lib/pkgconfig/pdfium.pc << EOF
         prefix=$VIPSHOME
         exec_prefix=\${prefix}
         libdir=\${exec_prefix}/lib
         includedir=\${prefix}/include
         Name: pdfium
         Description: pdfium
         Version: 4290
         Requires:
         Libs: -L\${libdir} -lpdfium
         Cflags: -I\${includedir}
    EOF

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

### poppler-glib

The Poppler PDF renderer, with a glib API. 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

If present, `vips_icc_import()`, `vips_icc_export()` and `vips_icc_transform()`
can be used to manipulate images with ICC profiles. 

### libspng

If present, libvips will load PNG files using libspng. At the moment, libpng
is still necessary for save.

### libpng

If libspng is not present and libpng is, libvips will load PNG files with
libpng. It will always save PNG files with libpng.

### libimagequant, quantizr

If one of these quantisation packages is present, libvips can write 8-bit
palette-ised PNGs and GIFs.

### ImageMagick, or optionally GraphicsMagick

If available, libvips adds support for loading and saving all
libMagick-supported image file types. You can enable and disable load and save
separately. 

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
enabling a package with such a large attack surface. 

### pangocairo

If available, libvips adds support for text rendering. You need the
package pangocairo 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.

### OpenJPEG

If available, libvips will read and write JPEG2000 images.

### libjxl

If available, libvips will read and write JPEG-XL images.

### OpenSlide

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

### libheif

If available, libvips can load and save HEIC and AVIF images. Your libheif (in
turn) needs to be built with the correct decoders and encoders. You can check
with eg.:

```
$ pkg-config libheif --print-variables
builtin_avif_decoder
builtin_avif_encoder
builtin_h265_decoder
builtin_h265_encoder
exec_prefix
includedir
libdir
pcfiledir
prefix
```

# Contributors

### Code Contributors

This project exists thanks to all the people who contribute. 

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