Image
is an image processing library for Elixir. It is based upon the fabulous vix library that provides a libvips wrapper for Elixir.
Image
is intended to provide well-documented common image processing functions in an idiomatic Elixir functional style as a layer above the very comprehensive set of functions in Vix
and libvips
.
As of version 0.18.0, Image
provides optional integration with Bumblebee allowing machine learning models to be deployed as part of an image processing pipeline.
Image
is also intended to be an idiomatic API layer over eVision (OpenCV). As of Image verison 0.9.0
, the Image.QRcode.decode/1
function is provided to decode QRcodes with the functionality to do so provided by eVision
. The eVision
integration is optional and currently considered experimental.
In a very simple image resizing benchmark, Image
is approximately 2 to 3 times faster than Mogrify
and uses about 5 times less memory.
The documentation can be found at https://hexdocs.pm/image.
Image
can be installed by adding image
to your list of dependencies in mix.exs
:
def deps do
[
{:image, "~> 0.28.0"}
]
end
Starting from v0.16.0 Vix which underpins Image
can use either pre-built binaries or platform provided binaries.
By default Vix
provides pre-built NIF and libvips
and uses them for operation. This makes deployment and release of your application a breeze. With this you don't have to install any compiler tools or libvips
to use Vix
. This is especially useful when using Image
with Livebook.
However the pre-built NIF or libvips does not include dependencies support all image formats and operations. If you require those formats or operations then you can bring your own libvips
by installing it manually and configure Vix
to use that instead. Vix
makes sure to generate relevant functions and documentation based on the dependencies you bring. For example, if you install libvips with tiff
support, vix will generate tiff
related bindings for you.
You can choose this using VIX_COMPILATION_MODE
environment variable. This variable must be set both during compilation and runtime. Possible values are:
-
PRECOMPILED_NIF_AND_LIBVIPS
(Default): Uses vix provided NIF and libvips. No need to install any additional dependencies. Big thanks to sharp library maintainers, pre-compiled libvips is based on: https://github.com/lovell/sharp-libvips/. -
PLATFORM_PROVIDED_LIBVIPS
: Uses platform provided libvips and NIF will be compiled during compilation phase. The following build tools are required generate theVix
NIF:- Install a platform specific
libvips
. This can be compiled from source (see https://www.libvips.org/install.html) or via a platform package manager. For example:- macOS: brew brew install libvips
- Linux: apt install libvips-dev For more details see
- Install
pkg-config
- Ensure a supported C compiler is installed
- Install a platform specific
Nx provides multi-dimensional arrays (tensors) and numerical definitions for Elixir. These tensors can also be used as an interchange format for binary image data. When Nx
is installed and Image
is compiled, the functions Image.to_nx/2
and Image.from_nx/1
are defined.
Nx
is required in order to support the functions in Image.Classification
. It is also required to support eVision and Bumblebee integrations.
- Add
Nx
to yourmix.exs
def deps do
[
...
{:nx, "~> 0.4"},
...
]
end
- Add a default
Nx
backend toconfig.exs
.Nx
supports a variety of backends that provide CPU and GPU acceleration. The CPU backend that provides the widest platform compatibility isEXLA.Backend
.
config :nx,
default_backend: EXLA.Backend
- Update dependencies
mix deps.get
Bumblebee provides pre-trained and transformer Neural Network models in Axon that can be used for a variety of image classification, segmentation and detection operations. When Bumblebee
is configured, the functions in Image.Classification
become available.
- Add
Bumblebee
andexla
to yourmix.exs
.exla
is required in order to provide CPU or GPU acceleration for the models so as to deliver acceptable performance.Nx
will be installed as a transitory dependency.
def deps do
[
...
{:bumblebee, "~> 0.1"},
{:exla, "~> 0.4"},
...
]
end
- Add a default Nx backend to
config.exs
.Nx
supports a variety of backends that provide CPU and GPU acceleration. The CPU backend that provides the widest platform compatibility isEXLA.Backend
.
config :nx,
default_backend: EXLA.Backend
- Update dependencies
mix deps.get
eVision (OpenCV) provides Elixir bindings to OpenCV, the most well-known computer vision library.
As of Image version 0.9.0, experimental support for eVision (OpenCV) is provided. There is extensive documentation on how to install eVision
and the required OpenCV. However to most cases the following should be enough:
- Add
eVision
to yourmix.exs
. exla may be optionally configured too, see theNx
installation section above.
def deps do
[
...
{:evision, "~> 0.1"},
...
]
end
- Update dependencies
mix deps.get
Then proceed as normal. eVision
will download a precompiled OpenCV
for the appropriate system architecture and compile both the NIF and Elixir code.
Vix
and libvips
offer various configuration parameters that affect debug output, image caching, concurrency of imaging operations and memory leak detection. Each of these options has reasonable defaults so no action is required in order to start using the library.
Vix
NIF code writes logs to stderr on certain errors. This is disabled by default. To enable logging set the VIX_LOG_ERROR
environment variable to true
.
The platform upon which Image
and Vix
stand is libvips, a C
library that performs the image manipulation. It's libvips
that delivers the speed, memory efficiency and functionality.
libvips
uses the GLib library which has configurable debug output. This output depends on the setting of the environment variable G_DEBUG
. The initial value will depend on the installation method of libvips
for a given system. It can be changed by setting the G_DEBUG
environment variable to one of the following:
-
fatal-warnings which causes GLib to abort the operation at the first call to g_warning() or g_critical().
-
fatal-criticals causes GLib to abort the operation at the first call to g_critical().
-
gc-friendly causes newly allocated memory that isn't directly initialized, as well as memory being freed to be reset to 0. The point here is to allow memory checkers and similar programs that use Boehm GC alike algorithms to produce more accurate results.
-
resident-modules causes all modules loaded by GModule will be made resident. This can be useful for tracking memory leaks in modules which are later unloaded; but it can also hide bugs where code is accessed after the module would have normally been unloaded.
-
bind-now-modules causes all modules loaded by GModule to bind their symbols at load time, even when the code uses %G_MODULE_BIND_LAZY.
To produce debug output for only the most critical issues, set G_DEBUG
as follows (in bash and compatible shells):
export G_DEBUG=fatal-criticals
The environment variable VIPS_LEAK
determines whether libvips
reports possible memory leaks. To enable leak detection (on bash
compatible systems):
export VIPS_LEAK=true
To stop leak detection:
unset VIPS_LEAK
Image
(because of Vix
and libvips
) will execute concurrent image operations using a number of system native threads (not BEAM processes). The number of threads available for concurrent image operations is configurable by either setting the environment variable VIPS_CONCURRENCY
or through a call to Image.put_concurrency/1
. The current number of configured threads is returned from Image.get_concurrency/0
.
The default number of threads is equal to the number of cores detected on the running system. This may create CPU contention with other workloads given that image processing is CPU intensive. Therefore it may be prudent to reduce the number of threads if overall system throughput is being affected.
In a future release, :image
will be split into several packages
:image
which will retain all the core components of image transformation based uponvix
andlibvips
.:image_nx
which will provide:nx
interoperability (and will depend on:image
):image_exif
which will provide metadata support (and will depend on:image
):image_classification
which will provide image classification (and will depend on:image
and:bumblebee
):image_generation
which will provide image generation (and will depend on:image
and:bumblebee
):image_detection
which will provide object detection (and will depend on:image
,:axon
,:axon_onnx
):image_qrcode
which will provide QRcode scanning and production (and will depend on:image
and:evision
):image_video
which will provide video frame extraction (and will depend on:image
and:evision
)
There are several considerations in the use of any image processing library and any NIF-based library:
-
If a NIF crashes it will likely bring down the BEAM virtual machine.
libvips
is a robust, time-tested library however this risk cannot be eliminated. -
Image processing is CPU intensive with its concurrent pipelining model and default concurrency level equal to the number of cores in the host machine, CPU starvation for other parts of the application is a possibility. In such cases, reducing the
libvips
concurrency is recommended. -
Image processing by its nature operates on external data and there have been exploits based upon maliciously crafted images. The two primary vectors are:
- An invalid image format that causes the image parser to crash and therefore crash the NIF and the BEAM
- Executable code embedded in image metadata (such as EXIF data) that if passed un-escaped to a web browser may result in arbitrary code execution.
In comparison to Imagemagick
that has a reported 638 CVEs, there have been only 8 CVE's reported for libvips
, each resolved in a very timely manner.