Viz2D

[TOC]


Original author	Amir Hassan (kallaballa) amir@viel-zu.org
Compatibility	OpenCV >= 4.7

What is Viz2D?

Viz2D offers a way of writing graphical (on- and offscreen) high performance applications with OpenCV. It is light-weight and unencumbered by QT or GTK licenses. It features vector graphics using NanoVG a GUI based on NanoGUI and (on supported systems) OpenCL/OpenGL and OpenCL/VAAPI interoperability. It should be included in OpenCV-contrib once it is ready.

Showcase

@youtube{yYnWkkZSK7Q}

Why Viz2D?

Please refer to the online demos in the following section to see at a glance what it can do for you.

OpenGL: Easy access to OpenGL.
GUI: Simple yet powerful user interfaces through NanoGUI.
Vector graphics: Elegant and fast vector graphics through NanoVG.
Font rendering: Loading of TTF-fonts and sophisticated rendering options.
Video pipeline: Through a simple Source/Sink system videos can be displayed, edited and saved.
Hardware acceleration: Automatic hardware acceleration usage where possible. (e.g. CL-GL sharing and VAAPI). Actually it is possible to write programs that run almost entirely on the GPU, given driver-features are available.
No more highgui with it's heavy dependencies, licenses and limitations.
WebAssembly support.

Online Demos

Please note that the following online demos are slower and/or have less features than the native versions.

Design Notes

Viz2D is not thread safe. Though it is possible to have several Viz2D objects in one or more threads and synchronize them using Viz2D::makeNonCurrent() and Viz2D::makeCurrent(). This is a limitation of GLFW3. That said, OpenCV algorithms are multi-threaded as usual.
Viz2D uses InputArray/OutputArray/InputOutputArray which gives you the option to work with Mat, std::vector and UMat. Anyway, you should prefer to use UMat whenever possible to automatically use hardware capabilities where available.
Access to different subsystems (opengl, framebuffer, nanovg and nanogui) is provided through "contexts". A context is simply a function that takes a functor, sets up the subsystem, executes the functor and tears-down the subsystem.
Contexts may not be nested.

For example, to create an OpenGL context and set the GL viewport: @code{.cpp} //Creates a Viz2D object for on screen rendering Ptr v2d = Viz2D::make(Size(WIDTH, HEIGHT), "GL viewport");

//Takes care of OpenGL states in the background v2d->gl([](const Size sz) { glViewPort(0, 0, sz.width, sz.height); }); @endcode

Requirements

C++20 (at the moment)
OpenGL 3.2 Compat/OpenGL ES 3.0 Core

Optional requirements

Support for OpenCL 1.2
Support for cl_khr_gl_sharing and cl_intel_va_api_media_sharing OpenCL extensions.
If you want CL-GL sharing on a recent Intel Platform (Gen8 - Gen12) you currently need to install compute-runtime from source and my OpenCV fork

Dependencies

OpenCV 4.x
GLEW
GLFW3
nanovg
nanogui

Tutorials

The tutorials are designed to be read one after the other to give you a good overview over the key concepts of Viz2D. After that you can move on to the samples.

\ref viz2d_display_image
\ref viz2d_vector_graphics
\ref viz2d_render_opengl
\ref viz2d_font_rendering
\ref viz2d_video_editing
\ref viz2d_font_with_gui

Samples

The goal of the samples is to show how to use Viz2D to the fullest. Also they show how to use Viz2D in conjunction with interop options to create programs that run mostly (the part the matters) on the GPU. They are also a good starting point for your own applications because they touch many key aspects and algorithms of OpenCV.

\ref viz2d_tetra
\ref viz2d_video
\ref viz2d_nanovg
\ref viz2d_shader
\ref viz2d_font
\ref viz2d_pedestrian
\ref viz2d_optflow
\ref viz2d_beauty

Attribution

The author of the bunny video is the Blender Foundation (Original video).
The author of the dance video is GNI Dance Company (Original video).
The author of the video used in the beauty-demo video is Kristen Leanne (Original video).

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