opencv/modules/video/src/optical_flow_io.cpp

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#include "precomp.hpp"
#include<iostream>
#include<fstream>

namespace cv {

const float FLOW_TAG_FLOAT = 202021.25f;
const char *FLOW_TAG_STRING = "PIEH";
CV_EXPORTS_W Mat readOpticalFlow( const String& path )
{
    Mat_<Point2f> flow;
    std::ifstream file(path.c_str(), std::ios_base::binary);
    if ( !file.good() )
        return std::move(flow); // no file - return empty matrix

    float tag;
    file.read((char*) &tag, sizeof(float));
    if ( tag != FLOW_TAG_FLOAT )
        return std::move(flow);

    int width, height;

    file.read((char*) &width, 4);
    file.read((char*) &height, 4);

    flow.create(height, width);

    for ( int i = 0; i < flow.rows; ++i )
    {
        for ( int j = 0; j < flow.cols; ++j )
        {
            Point2f u;
            file.read((char*) &u.x, sizeof(float));
            file.read((char*) &u.y, sizeof(float));
            if ( !file.good() )
            {
                flow.release();
                return std::move(flow);
            }

            flow(i, j) = u;
        }
    }
    file.close();
    return std::move(flow);
}

CV_EXPORTS_W bool writeOpticalFlow( const String& path, InputArray flow )
{
    const int nChannels = 2;

    Mat input = flow.getMat();
    if ( input.channels() != nChannels || input.depth() != CV_32F || path.length() == 0 )
        return false;

    std::ofstream file(path.c_str(), std::ofstream::binary);
    if ( !file.good() )
        return false;

    int nRows, nCols;

    nRows = (int) input.size().height;
    nCols = (int) input.size().width;

    const int headerSize = 12;
    char header[headerSize];
    memcpy(header, FLOW_TAG_STRING, 4);
    // size of ints is known - has been asserted in the current function
    memcpy(header + 4, reinterpret_cast<const char*>(&nCols), sizeof(nCols));
    memcpy(header + 8, reinterpret_cast<const char*>(&nRows), sizeof(nRows));
    file.write(header, headerSize);
    if ( !file.good() )
        return false;

    int row;
    char* p;
    for ( row = 0; row < nRows; row++ )
    {
        p = input.ptr<char>(row);
        file.write(p, nCols * nChannels * sizeof(float));
        if ( !file.good() )
            return false;
    }
    file.close();
    return true;
}

}