Building visp_java module

[akshay326]

• Equivalent to the opencv_java module - providing basic conversion functions and the JNI support too.
• Made a few edits. Will soon run the tests and provide results.
• Yet to be edited: android_test folder, CMakeLists.txt, generators/src folder, some files in pure_test folder

[akshay326]

Hi @fspindle @s-trinh

Need to define some java files as of OpenCV for the java module. But their directory structure is different from that of ViSP. Should separate the files in core/src and core/test?

[fspindle]

If it helps, we could introduce core/misc/java/src and core/misc/java/test as OpenCV

[akshay326]

Do vpMatrix, vpRect, vpPoint support any data type other than double? And vpPoint is a 3D point. Coz then there will be fewer functions for usage and testing in java - can develop it faster.

[akshay326]

@fspindle @s-trinh
Should I keep class name qualifiers as CamelCase - VpMatrix/VpException instead of vpMatrix/vpException in java?

[fspindle]

For me vpMatrix, vpRect, vpPoint should support only double as it is by now.

Concerning the class name, could you give us more details. I don't see why this is needed and didn't find similar things in OpenCV.

[akshay326]

You can refer here, C++ classes in OpenCV are named CamelCase way by default(like Mat and Rect). So there's no need to change class name in Java. But ViSP C++ classes like vpImage, vpRGBa are not CamelCase.

[akshay326]

@fspindle @s-trinh
Recently I made some edits in visp_java module. The build ran successfully on my device but fails on Travis (Refer here). Am I missing some code or header file? Does Travis CI has necessary JNI library?

[akshay326]

hi @fspindle @s-trinh
Do you have Travis configured to provide NDK support? I can't find sign of either JNI or NDK in this PR or in #307. You can refer this thread that the SDK that Travis provides by default is old/buggy. To get the support, refer this.

[fspindle]

Hi @Aks1996

We were in vacation last week and busy yesterday. I will check for travis today

[akshay326]

Hi @fspindle. Have a look at visp_io module demo eclipse project here

[akshay326]

Also get the visp_gui module demo eclipse project here. As @s-trinh recommended, I've used Java Swing for GUI - it's simple, platform independent and many developers will find it easy to use it.

Note that I haven't wrapped visp_gui for Java support. I think Android developers won't need visp_gui or visp_io modules at all (in fact the getPixels function in VpImageUChar and VpImageRGBa classes will suffice in Android).

I guess we should add these set of Java tutorials to the doc/tutorial/java folder.

[fspindle]

I don't know what I'm doing wrong, but I'm unable to run vpCore-Demo-Manual

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
	VpCameraParameters cannot be resolved to a type
	VpCameraParameters cannot be resolved to a type
	at Main.main(Main.java:39)

After a fresh ViSP build, what I have done in Eclipse:

• create a user library adding .../visp-build/bin/visp-320.jar external jar and set native library location to .../visp-build/lib
• open project vpCore-Demo-Manual from file system
• press button run

If I comment line 39 that brings the error I got an other one with VpMatrix

Exception in thread "main" java.lang.UnsatisfiedLinkError: org.visp.core.VpMatrix.n_vpMatrix(IID)J
	at org.visp.core.VpMatrix.n_vpMatrix(Native Method)
	at org.visp.core.VpMatrix.<init>(VpMatrix.java:26)
	at Main.main(Main.java:22)

Did I miss something ?

[akshay326]

Strange. Can you see libvisp_java320.so in .../visp-build/lib folder?

[fspindle]

Yes. I'm on OSX and I have libvisp_java320.dylib in .../visp-build/lib

[akshay326]

@fspindle I installed Eclipse on mac virtualbox. vpCore demo worked fine

[s-trinh]

@Aks1996 This looks great!

I think you can add frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); in VpDisplay to really close the window otherwise the application looks still running in Eclipse.

Maybe public String dump() could be replaced by the overrided public String toString()? I think this should allow using something like:

VpImageRGBa colorImage = new VpImageRGBa(3, 5, new VpRGBa((char)255,(char)0,(char)0,(char)255));
System.out.println(colorImage);

and public static void print(Object ... objs) in the demo project could be removed also?

[akshay326]

@s-trinh thanks for the suggestion, I'll add it now

@fspindle Are you able to run the demo now? I couldn't find anything except threads like this. Anyway try to clean the project and re-run

[fspindle]

Yes I succeed cleaning the project ;-)
It was nice to see that all your 3 demos were working on OSX and Ubuntu 16.04.

Current evaluation period will end July 9. Regarding your proposal we would be interested:

• to have a merge commit of PR Building visp_java module #323 as soon as your work arround visp_java with existing bindings (visp_core, visp_gui, visp_io) becomes stable. I think that we are very close. More than 100 files were modified yet. Waiting more will lead to too much changes to follow your work
• visp_gui binding could be improved with display functionalities of simple drawings (lines, cross) for Java
• then adding new java bindings for visp_imgproc, visp_detection (vpApriltag) could be a new PR for each
• next step would be to make a new java demo that uses an image as input, and detect the Apriltags

Then for Android we are interested :

• to have a tutorial for beginners to start with ViSP and Android (we are beginners ;-) It could be based on the project you already have done
• then to have the same demo (apriltag) but using the java bindings
• a PR with Android toolchain potential changes + a demo with live images that are displayed + filtered using visp_imgproc or using visp_core - vpImageFilter like in this tutorial could be also nice

I don't know if this is ok for you or if you have an other planned schedule ?
If you want, there is also the possibility to have a skype to discuss about that.
Let us know...

[akshay326]

First of all, thanks. It would've taken me a lot of time to draft such a concrete plan.
I'm all good with this plan(actually I was going to discuss closing of PR #323 with you in a few days). I understand that by making smaller PR's, the code will be easy to review later and changes easy to track.

Just want to make sure - are all the things(mentioned above) to be done before 9th July. Coz then I'll have to speed up a bit.

[fspindle]

No, all the plan is not to do before July 9, it was just a reminder. Do just your best

[akshay326]

We should close the PR now. I've executed the tutorials on Windows, with MinGW and it worked well.
Note that

• The appveyor is missing ant. So the java module is not building in appveyor tests
• On Windows, to use the IO module u need to have libpng and libjpeg. These are provided by GNU as 32 bit binaries only. So we need to use 32 bit JDK and Eclipse only
• In order to have 64 bit installation, I guess we need to compile libpng source code to generate binaries

[akshay326]

Once the PR is merged, I'll begin with simple GUI features - displayLine and others

[akshay326]

@fspindle ant is installed on appveyor but not detected during java build - its working well on mac.

Shall I push the GUI changes in this PR or make another PR?

[fspindle]

We will investigate why ant is not detected on appveyor. In the mean time, I will merge this PR. Next dev could be introduced in new PR. Thanks