OpenCV: compile images (Mats) into a strip

I created a very short C++ snippet to accumulate a series of Mats into a single Mat strip. It works like acc = acc + m - a new mat is added to the accumulator each time, then stored in the accumulator again.

#pragma once
#include <opencv2/opencv.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/imgcodecs.hpp>
#include <assert.h>

using namespace cv;

class MatStrip
{
public:
    Mat current;
    float scale;

    MatStrip(Mat start, float scale=0.3f):
        scale(scale)
    {
        resize(start, current, Size(start.cols * scale, start.rows * scale), 1.0, 1.0, INTER_CUBIC);
    }

    void add(const Mat &in_o)
    {
        Mat in;
        resize(in_o, in, Size(in_o.cols * scale, in_o.rows * scale), 1.0, 1.0, INTER_CUBIC);

        assert(in.type() == current.type());
        Size sz1 = current.size();
        Size sz2 = in.size();
        Mat im3(sz1.height, sz1.width+sz2.width, current.type());
        Mat left(im3, Rect(0, 0, sz1.width, sz1.height));
        current.copyTo(left);
        Mat right(im3, Rect(sz1.width, 0, sz2.width, sz2.height));
        in.copyTo(right);
        current = im3;
    }
};