Convert a vec type into a scalar type on opencv

Question

I am working on an image processing algorithm to detect markers. The code uses the opencv library and works perfectly fine. However I have been asked to put it into HDL using HLS to optimize the design. The thing is HLS doesn't allow the use of many structures and forms used in a standard code. My main problem here is that I use a variable defined as a Vec3b, which can't be synthesized by HLS.

I read this from the opencv documentation :

Vec : template class for short numerical vectors, a partial case of Matx
template<typename _Tp, int n> class Vec : public Matx<_Tp, n, 1> {...};
typedef Vec<uchar, 3> Vec3b;

Without entering into details about HLS, I would like to know if it is possible to replace the Vec3b type by one that could be synthesizable like Scalar_ or get it back as a simple Matx. Concerning the scalars, i found this in the doc :

It is possible to convert Vec<T,2> to/from Point_, Vec<T,3> to/from Point3_ , and Vec<T,4> to CvScalar or Scalar_. Use operator[] to access the elements of Vec.

I also put the whole code here in case it is needed. I am not the author, so it is written in spanish.

void recorroHorizontal(){
    for(int i=0;i<480;i++){
        colorAux=enHSB.at<Vec3b>(0,i);  //Cuidado con el acceso al revés
        int punto_anterior = (int)(colorAux[2]);
        for(int j=1;j<640-1;j++){
            colorAux=enHSB.at<Vec3b>(i,j);  //al reves j e i
            float brightness=colorAux[2];
            int brightnessi=(int)(brightness);
            h_pendientes[i][j]=brightnessi- punto_anterior;
            if(!(h_pendientes[i][j]>VALOR_PENDIENTE || h_pendientes[i][j]<-VALOR_PENDIENTE)){
                if(!(h_pendientes[i][j] + h_pendientes[i][j-1] >VALOR_PENDIENTE_TRUNCAR || h_pendientes[i][j] + h_pendientes[i][j+1]<-VALOR_PENDIENTE_TRUNCAR)){
                    h_pendientes[i][j]=0;
                }
            }
            if(j<2 || i<2 || 640-1 ==i){h_pendientes[i][j]=0;}
            punto_anterior=brightnessi;
            original[i][j]=brightnessi;
        }
    }
}

@ZdaR HDL stands for Hardware Description Language, a language describing an Hardware IP. HLS stands for High Level Synthesis, which is a method used to translate a high level language such as C++ into HDL. — Valentin Dubois, Jun 26 '17 at 14:07

score 0 · Accepted Answer · answered Jun 26 '17 at 14:14

In the end I replaced the Vec3b type with a table of Scalar (or hls::Saclar to be more precise, a structure from hls_video.h). I then access to the data in this table with .val[].

It seems to work, even if it may be a problem when communicating with the software.

Convert a vec type into a scalar type on opencv

1 Answers1