B4A Library OpenCV 3.x

cesarcm · Dec 5, 2020

JordiCP,

Probably my last question (I hope so) ...

I have to migrate these lines as well:

Mat X = Mat::zeros(13,6,CV_32FC1);
Mat mat43= Mat::eye(4,3,CV_32FC1); //this is a submatrix at position (4,4)

Mat aux = X.colRange(4,7).rowRange(4,8); // you are pointing to submatrix 4x3 at X(4,4)
mat43.copyTo(aux);

Any tip helps a lot

Thanks
Regards,
Cear

JordiCP · Dec 5, 2020

cesarcm said:
Mat X = Mat::zeros(13,6,CV_32FC1);
Mat mat43= Mat::eye(4,3,CV_32FC1); //this is a submatrix at position (4,4)

Mat aux = X.colRange(4,7).rowRange(4,8); // you are pointing to submatrix 4x3 at X(4,4)
mat43.copyTo(aux);

Untested, but should be something similar to this

Code:

    Dim mType As OCVCvType

    Dim X as OCVMat 
    X = X.zeros(13,6,mType.CV_32FC1)
    Dim mat43 As OCVMat = X.submat(4,8,4,7) 
    Dim aux As OCVMat
    aux = aux.eye(4,3, mType.CV_32FC1)
    mat43.copyTo(aux)

I'd recommend to add a code module to your project with some static helper methods. These become very useful to make the final code more readable

Code:

Sub CreateScalar(X As Double) As OCVScalar
    Dim sc As OCVScalar
    sc.Initialize(X)
    Return sc
End Sub

Sub CreateScalar2(X As Double, Y As Double) As OCVScalar
    Dim sc As OCVScalar
    sc.Initialize2(X, Y)
    Return sc    
End Sub

Sub CreateScalar3(X As Double, Y As Double, Z As Double) As OCVScalar
    Dim sc As OCVScalar
    sc.Initialize3(X, Y, Z)
    Return sc    
End Sub

Sub CreateSize(W As Double, H As Double) As OCVSize
    Dim sz As OCVSize
    sz.Initialize2(Array As Double(W,H))
    Return sz
End Sub

Sub CreateMat(rows As Int, cols As Int, cType As Int) As OCVMat
    Dim m As OCVMat
    m.Initialize2(rows, cols, cType)
    Return m
End Sub

Sub CreateEyeMat(rows As Int, cols As Int, cType As Int) As OCVMat
    Dim m As OCVMat 
    m = m.eye(rows, cols, cType)
    Return m
End Sub

Sub CreateZeroMat(rows As Int, cols As Int, cType As Int) As OCVMat
    Dim m As OCVMat 
    m = m.zeros(rows, cols, cType)
    Return m
End Sub

cesarcm · Dec 5, 2020

JordiCP,

Perfect!

Please, one more tip ...

// from Javascript
let means_c3 = cv.matFromArray(1, 1, cv.CV_32FC3, [mean.data64F[0], mean.data64F[1], mean.data64F[2]]);

PS: I guess that I have to use OCVMatOfDouble .. Am I right?

Thanks
Regards,
Cesar

JordiCP · Dec 5, 2020

Yes, but I guess that you can also work with OCVMat.
(Untested)

Code:

Dim mm As OCVMatOfDouble
mm.Initialize3(Array As Double(  firstElement, secondElement, ...    ))

'or

Dim mm As OCVMat
mm.initialize2(1,1, mType.CV_32FC3)
mm.put(0,0, Array as Double( firsElement, secondElement, tihrdElement))

cesarcm · Dec 5, 2020

YOU ROCK!

But how can I get mean.data64F? or is it not necessary?

let mean = new cv.Mat();
let stdDev = new cv.Mat();
let t1 = new cv.Mat();
cv.meanStdDev(signal, mean, stdDev, t1);

let means_c3 = cv.matFromArray(1, 1, cv.CV_32FC3, [mean.data64F[0], mean.data64F[1], mean.data64F[2]]);

Thanks for all.
Regards,
Cesar

JordiCP · Dec 5, 2020

It's a bit difficult to follow without seeing the whole code.

If I understood correctly

Code:

Dim mean, stdDev, t1 as OCVMat
Dim mCore as OCVCore
mCore.meanStdDev( signal, mean, stdDev, t1)  

Dim meanVals() as Double = means.get5(0,0)     '<-- each 'getX' suffix corresponds to a different data type and must match the OCV Type

Dim means_c3 as OCVMat    '<-- now the code needs a Mat of floats. There is a "convertTo' method that casts element, but we can extract them and build a new OCVMat. Need to test it,
means_c3.initialize2(1,1, mType.CV_32FC3)
means_c3.put1(0,0, Array as float( meanVals(0), meanVals(1), meanVals(2) ))

cesarcm · Dec 5, 2020

JordiCP,

Thanks ?

Probably my last question (I hope so)..

Any idea to convert these lines? (in blue color)

For (var i = 1; i < signal.rows; i++) {
' If (lrescan == True) {
' let adjV = new cv.MatVector();

' let adjR = cv.matFromArray(signal.rows, 1, cv.CV_32FC1,
' new Array(signal.rows).fill(0).fill(diff.data32F[(i-1)*3], i, signal.rows));

' let adjG = cv.matFromArray(signal.rows, 1, cv.CV_32FC1,
' new Array(signal.rows).fill(0).fill(diff.data32F[(i-1)*3+1], i, signal.rows));

' let adjB = cv.matFromArray(signal.rows, 1, cv.CV_32FC1,
' new Array(signal.rows).fill(0).fill(diff.data32F[(i-1)*3+2], i, signal.rows));

I guess that I have to create the array manually ... I do think that B4A has a function like Javascript for "new Array" like that

Thanks for all
Regards,
Cesar

JordiCP · Dec 5, 2020

I guess that 'signal' and 'diff' are OCVMat with depth=3 (cv_32FC3) and contains R,G,B channels

If you are accessing single channel elements from diff, you can first split it into 3 channels, it will be easier to manage. As it is done HERE

Regarding the code

Code:

Dim channels As List
channels.Initialize
mCore.split( diff, channels)     '<-- Statically declare mCore as OCVCore 
Dim redChannel  As OCVMat = channels.Get(0)
Dim greenChannel  As OCVMat = channels.Get(1)
Dim blueChannel As OCVMat = channels.Get(2)

  Dim myReadData( signal.rows) as Float    'Only declare it once. Will be reused.

For i=1 to signal.rows()-1

  '---- Red channel ----
  Dim adjR as OCVMat
  adjR.initialize( signal.rows, 1, mType.CV_32F1)
  Dim valData(1) as Float
  redChannel.get3( i-1, 1, valData) 
  for j=0 to i-1
    myReadData(j) = 0
  Next
  For j=i to signal.rows-1
    myReadData(j) = valData(0)
  Next 
  adjR.put1(0,0, myReadData)

  '---- Green channel ----
  Dim adjG as OCVMat
  adjG.initialize( signal.rows, 1, mType.CV_32F1)
  Dim valData(1) as Float
  greenChannel.get3( i-1, 1, valData) 
  Dim myReadData( signal.rows) as Float
  for j=0 to i-1
    myReadData(j) = 0
  Next
  For j=i to signal.rows-1
    myReadData(j) = valData(0)
  Next 
  adjG.put1(0,0, myReadData)

 ' Do the same with the Blue channel

Next

Pls PM me if you have more issues

cesarcm · Dec 5, 2020

(clap clap clap)

Simple and beauty! Congrats!
Thanks for all.
Kind regards,
Cesar

PS: I am trying to convert all source-code to B4A until next Monday since I will have an presentation

cesarcm · Dec 5, 2020

Last question for today (I promisse it)

C++ code:

// New values
Scalar means = mean(frameRGB, mask);

// Add new values to raw signal buffer
double values[] = {means(0), means(1), means(2)};

signal.push_back(Mat(1, 3, CV_64F, values));

Thanks.
Regards,
Cesar

JordiCP · Dec 5, 2020

Java OpenCV only allows to push_back Mats, so the scalar values must be converted to a single row Mat.

Test if this works (code is assuming that signal.cols equals 3), may need some fine tuning.

Code:

Dim means as OCVScalar = mCore.mean(frameRGB, mask)
Dim values() as Double = means.val
Dim newMat As OCVMat
newMat.Initialize2(1, signal.cols, mType.CV_64FC1)
newMat.put(0, 0, values)
signal.push_back( newMat )

Good luck with the presentation, don't forget to add me to the credits ?

cesarcm · Dec 5, 2020

JordiCP,

Credits? of course!!! ???

As like I have mentioned before: if everything goes right you will get an extra bonus (donation) or a monthly basis fee

Thanks
Regards,
Cesar

cesarcm · Dec 6, 2020

JordiCP,

Maybe a stupid question... (or not) ...

Should I always to "Initialize" an OCVMat object?

Exemple:

Dim myObj As OCVMat
myObj.initialize '???
myObj.zeros(10, 10, mType.mCvt.CV_32FC1)

Thanks
Regards,
Cesar

cesarcm · Dec 6, 2020

JordiCP,

DFT function has 4 parameters:

4th param => nonZeroRows as Int

In my libraries of DFT for Javascript / C++ / Python, DFT has only 2 o3 parameters

And I am get confused to how to convert the code below (in red):

// Javascript
timeToFrequency(signal, magnitude) {
// Prepare planes
let planes = new cv.MatVector();
planes.push_back(signal);
planes.push_back(new cv.Mat.zeros(signal.rows, 1, cv.CV_32F))
//let powerSpectrum = new cv.Mat();
cv.merge(planes, signal);

// Fourier transform
cv.dft(signal, signal, cv.DFT_COMPLEX_OUTPUT);
if (magnitude) {
cv.split(signal, planes); // planes[0] = Re(DFT(I), planes[1] = Im(DFT(I))
cv.magnitude(planes.get(0), planes.get(1), signal); // signal = magnitude
}
}

Thanks.
Regards,
Cesar

cesarcm · Dec 6, 2020

JordiCP<

Same source code as last message but in C++

void timeToFrequency(InputArray _a, OutputArray _b, bool magnitude) {

// Prepare planes
Mat a = _a.getMat();
Mat planes[] = {cv::Mat_<float>(a), cv::Mat::zeros(a.size(), CV_32F)};
Mat powerSpectrum;
merge(planes, 2, powerSpectrum);

// Fourier transform
dft(powerSpectrum, powerSpectrum, DFT_COMPLEX_OUTPUT);

if (magnitude) {
split(powerSpectrum, planes);
cv::magnitude(planes[0], planes[1], planes[0]);
planes[0].copyTo(_b);
} else {
powerSpectrum.copyTo(_b);
}
}

Thanks.
Regards,
Cesar

JordiCP · Dec 6, 2020

cesarcm said:
Should I always to "Initialize

It depends. In this case 'zeros' is a static method that returns a OCVMat.
So the original Mat does not need to be initialized, but the call should be

Code:

myObj = myObj.zeros(10, 10, mType.mCvt.CV_32FC1)

JordiCP · Dec 6, 2020

cesarcm said:
if (magnitude) {
cv.split(signal, planes); // planes[0] = Re(DFT(I), planes[1] = Im(DFT(I))
cv.magnitude(planes.get(0), planes.get(1), signal); // signal = magnitude
}

You must declare planes as a list. Remember the code I sent yesterday with the split method.

cesarcm · Dec 6, 2020

Mr.J,

Perfect! Thanks a lot!

Regarding DFT:

DFT function has 4 parameters:

4th param => nonZeroRows as Int

In my libraries of DFT for Javascript / C++ / Python, DFT has only 2 o3 parameters

I presume that you use this 4th parameter to calculate the next power of 2, right?

Regards,
Cesar

cesarcm · Dec 6, 2020

JordiCP,

My original cvMat is NOT power2 compatible ... (signal As OCVMat)

How to copy it into a new OCVMat with next power2 allocated?

Thanks.
Regards,
Cesar

JordiCP · Dec 6, 2020

cesarcm said:
I presume that you use this 4th parameter to calculate the next power of 2, right?

Yes, it seems so.
Note also that there is a simpler method, dft1, which only needs 2 params, src and dst.

B4A Library OpenCV 3.x

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