B4J Question jopencv, b4j, converting to an array

[michaelleewebb]

trying to change video0,video1, backsub0,backsub1 into arrays. appears to me that OCVBackgroundSubtractorMOG2 can't be converted to an array. can someone read the error message i get when i run the program in debug mode. confirm i'm right, maybe explain a work around. maybe my sytax is wrong ?
in case i'm not clear, i have:
Dim Video0 As OCVVideo
Dim Video1 As OCVVideo
Dim BackSub0 As OCVBackgroundSubtractorMOG2 = Video0.createBackgroundSubtractorMOG2(10,98,False)
Dim BackSub1 As OCVBackgroundSubtractorMOG2 = Video1.createBackgroundSubtractorMOG2(10,98,False)
i wish to have:
dim Videos(2) as OCVVideo
dim BackSubs(2) As OCVBackgroundSubtractorMOG2

    Dim Video0 As  OCVVideo
    Dim Video1 As OCVVideo
   
    Dim BackSub0 As OCVBackgroundSubtractorMOG2 = Video0.createBackgroundSubtractorMOG2(10,98,False)
    Dim BackSub1 As OCVBackgroundSubtractorMOG2 = Video1.createBackgroundSubtractorMOG2(10,98,False)
   
   
    Dim NumOfTripWires As Int = 3
    Dim Videos(NumOfTripWires) As OCVVideo
    Dim WireCounter As Int = 0
    Do Until WireCounter = NumOfTripWires
        Dim BackSubs(WireCounter) As OCVBackgroundSubtractorMOG2 = Videos(WireCounter).createBackgroundSubtractorMOG2(10,98,False)
        WireCounter = WireCounter + 1
    Loop

error is this line:
Dim BackSubs(WireCounter) As OCVBackgroundSubtractorMOG2 = Videos(WireCounter).createBackgroundSubtractorMOG2(10,98,False)
this is error message:
Compiling generated Java code. Error
B4J line: 183
Dim BackSubs(WireCounter) As OCVBackgroundSubtra
src\b4j\example\main.java:289: error: incompatible types: BackgroundSubtractorMOG2 cannot be converted to BackgroundSubtractorMOG2[]
_backsubs = (com.b4jcv.video.BackgroundSubtractorMOG2[])(_videos[_wirecounter].createBackgroundSubtractorMOG2((int) (10),98,anywheresoftware.b4a.keywords.Common.False));
^
1 error

 

[JordiCP]

With this line

    Dim BackSubs(WireCounter) As OCVBackgroundSubtractorMOG2 = Videos(WireCounter).createBackgroundSubtractorMOG2(10,98,False)

you were declaring an OCVBackgroundSubtractorMOG2 array of different length each time and assigning it to a single OCVBackgroundSubtractorMOG2 Object, which is programmatically incorrect.

The correct syntax should be

    Dim NumOfTripWires As Int = 3
    Dim Videos(NumOfTripWires) As OCVVideo
    Dim BackSubs(NumOfTripWires) As OCVBackgroundSubtractorMOG2        ' Declare the array once
    Dim WireCounter As Int = 0
    Do Until WireCounter = NumOfTripWires
        BackSubs(WireCounter) = Videos(WireCounter).createBackgroundSubtractorMOG2(10,98,False)       ' and assign each one of the elements in the Do-Until Loop
        WireCounter = WireCounter + 1
    Loop

----- EDIT ------

Well, the above will fail because there is a bug in the current jOpenCV library which will throw an error when declaring an OCVBackgroundSubtractorMOG2 object

Dim BackSubs(NumOfTripWires) As OCVBackgroundSubtractorMOG2         ' This will fail, either declaring a single item or an array, because a bug in the lib

A temporary workaround could be (the only constraint is that NumOfTripWires must be known at code time)

   Dim NumOfTripWires As Int = 3
   Dim Videos(NumOfTripWires) As OCVVideo
   Dim BackSubs(NumOfTripWires) As OCVBackgroundSubtractorMOG2 = Array as OCVBackgroundSubtractorMOG2( _
      Videos(0).createBackgroundSubtractorMOG2(10,98,False), _
      Videos(1).createBackgroundSubtractorMOG2(10,98,False), _
      Videos(2).createBackgroundSubtractorMOG2(10,98,False) _
   )

Also note that you don't need to declare Videos(3). You can declare just one and then create the backgroundSubstractors from the same instance

   Dim NumOfTripWires As Int = 3
   Dim Video As OCVVideo
   Dim BackSubs(NumOfTripWires) As OCVBackgroundSubtractorMOG2 = Array as OCVBackgroundSubtractorMOG2( _
      Video.createBackgroundSubtractorMOG2(10,98,False), _
      Video.createBackgroundSubtractorMOG2(10,98,False), _
      Video.createBackgroundSubtractorMOG2(10,98,False) _
   )

 

[michaelleewebb]

i only need one video, very kool. look like the work around will work for me, i know the number of tripwires ahead of time. i'll give it a try and get back with the results shortly

 

[michaelleewebb]

yes that worked very well. from 573 lines of code to 280. problem solved. thank you !!