This blog post covers my lazy sunday afternoon where I tried to get my ancient Sudoku project running again.
(If you wonder why those numbers dance around - depending on what the application recognises different solutions are calculated and presented ... yes it's not perfect ;-) )
Years ago I played around with the idea of solving Sudokus with an algorithm and used JavaFX and OpenCV to do it. Quite an unusual combination, then as it is now - but it wasn't really a bad experience at all. In my view the Java OpenCV API is quite usable, and as such I wanted to prove at least for me that I could get it to run (albeit its far from perfect ;-))
I remember spending hours playing around with different filters and effects, always proud of new things I discovered.
Today, I decided to breathe life again into this project, let's see which problems I'll encounter.
First, getting source code from github still works, my last commit already 4 years ago, zero contributors along all those years, that's what a normal OSS project looks like ;-).
I try to revive it again, just the desktop version of it, leaving the android version on my todo list.
First obstacle I hit is to compile it, OpenCV is missing on my system.OpenCV doesn't have a proper maven integration, there is an ancient issue about this, nobody had the mood or skills to solve it yet.
Update: I learned that there is somekind of maven integration in the meantime! Great!! Anyway, I build OpenCV from scratch for this article, maybe I'll have a go at the maven build another time.
First, I want to mention that there are several package mangers which provide prebuilt binaries for OpenCV, homebrew for example. It may well be that this is an option you prefer If you stumbled on this page by googling (seems to be rather unlikely but well).
Ok, in the meantime they reached version 4.3.0 something, I download the zip from here but I'm too dumb to find build instructions ... No obvious links are neither on the main page nor documentation. (They surely exist but I just didn't see them apparently)
Finally, I found them.
There are numerous steps to follow, you'll need Cmake and quite some time during compilation, educated guesses what to choose, we'll go with defaults for the first try. Unzip it somewhere, I choose
~/custom-builds/opencv-4.3.0/src/
since we have the famous 'out of source' build CMake proposes as best practice. This means that there is a dedicated directory for build artifacts.
As such I choose following setup:
~/custom-builds/opencv-3.4.0/src/<actual contents of zip>
~/custom-builds/opencv-3.4.0/target/<here build artefacts will be placed>
I jump to this target directory and execute there following command:
cmake ../src/
... then CMake does it's job, checks for all available goodies found on my system, I pray that the right ones I need are contained, otherwise I will have to configure it and fight the dragons of OpenCV ... again.
... But it seems that I'm lucky, at the end of the cmake output it says something about java bindings, which I'm interested in, as such it should compile it like I want.
What I personally don't want is that it installs itself to some system directory, which will definitely pollute my system and break some stuff already fine tuned there, as such I have to Issue CMake again with a proper parameter:
cmake ../src -DCMAKE_INSTALL_PREFIX=../out
(Pro tip: delete your target directory beforehand completely, thank me later). This would put OpenCv then to a directory:
~/custom-builds/opencv-3.4.0/out/
Like that I can delete it again without any trace.
I'm quite sure I don't need 98% what is going to be compiled, and some magic incantation of CMake or it's configuration would prevent compiling and linking it, but I don't want to go down that road, not today.
After configuring CMake you have to invoke 'make' as well, and do it with full throttle, meaning with some concurrent threads to speed things up (yes, you can get your coffee break since it will take a while).
That said, still being in the target directory, now execute
make -j8
which will use 8 threads to compile OpenCV (takes 5min+ on my machine)
In the meantime, I want to mention it is a huge accomplishment that building from scratch 'just works' for many environments, be it MacOsX, Windows, Linux ... this is much work and should be praised!
Everytime I compile something I'm amazed if it works first time without much hassle.... I've spent already countless hours on resolving build problems, it is a major time drain.
Anyhow, make succeeded, and all build outputs are already somewhere lying in the target dir. But with
make install
everything important for the runtime will be put to the ../out directory.
Specifically, one can find dylibs in the out/lib and out/share/java/opencv4 directory.
I tried to make this easy, all you have to do is to edit the main pom file and tweak some properties and point to your opencv installation directories. Here is an example configuration:
After you've changed those settings to your liking, enter following command:
mvn initialize -Pinstall-opencv -N
Now you should be ready to go, build the project with
mvn package
It shouldn't take too long, and everything should be set up correctly. OpenCV has many dylibs / dlls, which are referenced in this project, but via maven property filtering and some pseudo magic everything should just work.
You can fire it up via (being in the main directory of the project)
java -jar sudoku-javafx/target/sudoku-javafx-2020.1-SNAPSHOT-jar-with-dependencies.jar
A JavaFx Gui should appear, on the first invocation you maybe have to tell your Os that it is ok to give SudokuFx access to the webcam.
I've blogged about this project in several other blogposts, maybe you want to read them as well.
This post is referencing code state from the 2020.1 resurrection release.
To sum up, compiling OpenCV turned out to be much easier now as it was years ago, only my code was a little bitrotten - still is - but at least it should be easier to get it to run now than it was before this little article.
Thanks for reading!
 |
| screen capture of application |
Years ago I played around with the idea of solving Sudokus with an algorithm and used JavaFX and OpenCV to do it. Quite an unusual combination, then as it is now - but it wasn't really a bad experience at all. In my view the Java OpenCV API is quite usable, and as such I wanted to prove at least for me that I could get it to run (albeit its far from perfect ;-))
I remember spending hours playing around with different filters and effects, always proud of new things I discovered.
Today, I decided to breathe life again into this project, let's see which problems I'll encounter.
First, getting source code from github still works, my last commit already 4 years ago, zero contributors along all those years, that's what a normal OSS project looks like ;-).
I try to revive it again, just the desktop version of it, leaving the android version on my todo list.
First obstacle I hit is to compile it, OpenCV is missing on my system.
Update: I learned that there is somekind of maven integration in the meantime! Great!! Anyway, I build OpenCV from scratch for this article, maybe I'll have a go at the maven build another time.
Step 1 - download and compile OpenCV 4.3.0
First, I want to mention that there are several package mangers which provide prebuilt binaries for OpenCV, homebrew for example. It may well be that this is an option you prefer If you stumbled on this page by googling (seems to be rather unlikely but well).
Ok, in the meantime they reached version 4.3.0 something, I download the zip from here but I'm too dumb to find build instructions ... No obvious links are neither on the main page nor documentation. (They surely exist but I just didn't see them apparently)
Finally, I found them.
There are numerous steps to follow, you'll need Cmake and quite some time during compilation, educated guesses what to choose, we'll go with defaults for the first try. Unzip it somewhere, I choose
~/custom-builds/opencv-4.3.0/src/
since we have the famous 'out of source' build CMake proposes as best practice. This means that there is a dedicated directory for build artifacts.
As such I choose following setup:
~/custom-builds/opencv-3.4.0/src/<actual contents of zip>
~/custom-builds/opencv-3.4.0/target/<here build artefacts will be placed>
I jump to this target directory and execute there following command:
cmake ../src/
... then CMake does it's job, checks for all available goodies found on my system, I pray that the right ones I need are contained, otherwise I will have to configure it and fight the dragons of OpenCV ... again.
... But it seems that I'm lucky, at the end of the cmake output it says something about java bindings, which I'm interested in, as such it should compile it like I want.
What I personally don't want is that it installs itself to some system directory, which will definitely pollute my system and break some stuff already fine tuned there, as such I have to Issue CMake again with a proper parameter:
cmake ../src -DCMAKE_INSTALL_PREFIX=../out
(Pro tip: delete your target directory beforehand completely, thank me later). This would put OpenCv then to a directory:
~/custom-builds/opencv-3.4.0/out/
Like that I can delete it again without any trace.
I'm quite sure I don't need 98% what is going to be compiled, and some magic incantation of CMake or it's configuration would prevent compiling and linking it, but I don't want to go down that road, not today.
After configuring CMake you have to invoke 'make' as well, and do it with full throttle, meaning with some concurrent threads to speed things up (yes, you can get your coffee break since it will take a while).
That said, still being in the target directory, now execute
make -j8
which will use 8 threads to compile OpenCV (takes 5min+ on my machine)
In the meantime, I want to mention it is a huge accomplishment that building from scratch 'just works' for many environments, be it MacOsX, Windows, Linux ... this is much work and should be praised!
Everytime I compile something I'm amazed if it works first time without much hassle.... I've spent already countless hours on resolving build problems, it is a major time drain.
Anyhow, make succeeded, and all build outputs are already somewhere lying in the target dir. But with
make install
everything important for the runtime will be put to the ../out directory.
Specifically, one can find dylibs in the out/lib and out/share/java/opencv4 directory.
Step 2 - Make OpenCV available to Maven
<properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <scala.major.version>2.12</scala.major.version> <scala.full.version>${scala.major.version}.10</scala.full.version> <opencv.major.version>4.3</opencv.major.version> <opencv.full.version>${opencv.major.version}.0</opencv.full.version> <opencv.install.path>/Users/lad/custom-builds/opencv-4.3.0/out/</opencv.install.path> <opencv.java.jar>${opencv.install.path}share/java/opencv4/opencv-430.jar</opencv.java.jar> </properties>
After you've changed those settings to your liking, enter following command:
mvn initialize -Pinstall-opencv -N
Now you should be ready to go, build the project with
mvn package
It shouldn't take too long, and everything should be set up correctly. OpenCV has many dylibs / dlls, which are referenced in this project, but via maven property filtering and some pseudo magic everything should just work.
You can fire it up via (being in the main directory of the project)
java -jar sudoku-javafx/target/sudoku-javafx-2020.1-SNAPSHOT-jar-with-dependencies.jar
A JavaFx Gui should appear, on the first invocation you maybe have to tell your Os that it is ok to give SudokuFx access to the webcam.
I've blogged about this project in several other blogposts, maybe you want to read them as well.
This post is referencing code state from the 2020.1 resurrection release.
To sum up, compiling OpenCV turned out to be much easier now as it was years ago, only my code was a little bitrotten - still is - but at least it should be easier to get it to run now than it was before this little article.
Thanks for reading!
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