Introduction (?)

In my research, I came across a situation where it would be better to use AR markers, so I searched for a library that could recognize AR markers and came across something called ArUco. This article shows you how to get started with the ArUco library. I'm using Java because I can't use C / C ++ / C #.

I also declare that using OpenCV in Java can be a hassle. It seems that very few people are using it. There are few code examples and questions even in English. However, it runs faster than Python, so I think it has many uses.

OpenCV OpenCV is an open source library for image processing and is fairly widely used. The ideas are so broadly covered that you can generally combine functions.

OpenCV_Contrib OpenCV_Contrib is a library that focuses on the latest technology in OpenCV and is treated as an auxiliary. Also, if you only use the main body, you do not need to build. You can get it by downloading from OpenCV.org (official page). However, it seems that OpenCV_Contrib needs to be built by myself probably because it is treated as an auxiliary. This page describes how to build this

ArUco A library that can do AR. You can generate and recognize AR markers. (The code etc. will be described next time.)

Preparation

download

What to download	Description
OpenCV project source	Be sure to match the version with Conrib. I am Version: 3.4.I'm using 4.
OpenCV_Contrib project source	Be sure to match the version with Conrib. I am Version: 3.4.I'm using 4.
CMake	Appropriately.
Visual Studio	I used Visual Studio Community 2017.(C++I think I had to put in a compiler ...)
Python	You probably need it even when using Java. I am Version: 3.7.I'm using 1.
JDK	I am using Java8u191.
Ant	I am Version: 1.10.I am using 5.

Installation

Expand the project source of OpenCV and OpenCV_Contrib. Please install CMake and Visual Studio by yourself.

Java, Ant environment variables

Is this a songwriter unexpectedly? So, if you do not set it correctly, you will not be able to build. (I was addicted here)

What to download	Description
`ANT_HOME`	The extracted Ant folder. (ex: `C:\SOFT_File\apache-ant-1.10.5`)
`JAVA_HOME`	The folder where Java is installed. (ex: `C:\Program Files\Java\jdk1.8.0_191`)
`Path`	The following contentsadd toplease. `C:\Program Files\CMake\bin`, `%ANT_HOME%\bin`, `%JAVA_HOME%\bin` (ex: `C:\Program Files\CMake\bin;%ANT_HOME%\bin;%JAVA_HOME%\bin;` )

Run CMake

It seems that you have to prepare for the build with CMake before building, so I will do it.

item	value
`Where is the source code`	Specify the path of the extracted folder. (ex: `C:/SOFT_File/opencv-3.4.4`)
`Where to build the binaries`	I created a build folder under the extracted main library and specified the path of this folder. (ex: `C:/SOFT_File/opencv-3.4.4/build`)

After specifying these, press "Configure". At this time, specify the compiler. This time we will use Visual Studio for the build, so let's specify Visual Studio (the one that matches the version). (I chose "Visual Studio 2017 Win64")

Then, a red one pops out, but don't worry. Enable both the "Grouped" and "Advanced" checkboxes.

item	value
`OPENCV_EXTRA_MODULES_PATH`	Deployed OpenCV_In the parent folder of ContribModules belowIs specified. (Deployed OpenCV_Not the parent folder of Contrib)

Press Configure again.

Disable the "BUILD_SHARED_LIBS" checkbox. (Reference: http://answers.opencv.org/question/189941/java-cant-find-dependent-libraries/)

Press Configure again.

Please enable the check box of "BUILD_FAT_JAVA_LIB".

Press Configure again.

At this time, if there is no red object, it is OK. If so, please correct it.

Now check the log output. In particular, make sure that Java is as follows. (It's just an example)

  Java:                          export all functions
    ant:                         C:/SOFT_File/apache-ant-1.10.5/bin/ant.bat (ver 1.10.5)
    JNI:                         C:/Program Files/Java/jdk1.8.0_191/include C:/Program Files/Java/jdk1.8.0_191/include/win32 C:/Program Files/Java/jdk1.8.0_191/include
    Java wrappers:               YES
    Java tests:                  YES

Full text: https://pastebin.com/u2Qiy5EL

If there is no problem, Press "Generate".

When you're done, press "Open Project". This will launch Visual Studio. (To the next section)

Build with Visual Studio

Wait for a while to read various things. Set "Release" / "Debug" in the middle to "Release". Also, please set the next one to "x64". Press "Build"-> "Batch Build" on the menu bar above. Check both ʻALL_BUILD and ʻINSTALL and execute.

If you wait for a while (about 1h?), It should be created in the folder specified by Where to build the binaries in CMake (ex: (OpenCV extraction folder) / build / install).