well you could try to use the FileStorage wo write xml/yml, but unfortunately it won't be able to read it back in again (reading VecfX seems limited to 4 elems).
messing with exr seems quite daring, too, so let's just roll our own storage
(note, that this is a very special case, limited to 2d / Vec5f) :
#include "opencv2/opencv.hpp"
#include <iostream>
using namespace cv;
using namespace std;
typedef Vec<float,5> Vec5f;
#include <fstream>
#define SPARSEBINARY
bool write2d(const char *fn, SparseMat &m)
{
ofstream s(fn, ios::out | ios::binary);
int h = m.hdr->size[0];
int w = m.hdr->size[1];
#ifdef SPARSEBINARY
s.write((char*)&h, sizeof(int));
s.write((char*)&w, sizeof(int));
#else // text
s << h << " " << w << endl;
#endif
for (int i=0; i<h; i++)
{
for (int j=0; j<w; j++)
{
if (0 == m.ptr(i,j,false))
continue;
Vec5f e = m.ref<Vec5f>(i,j);
#ifdef SPARSEBINARY
s.write((char*)&i, sizeof(int));
s.write((char*)&j, sizeof(int));
s.write((char*)&e, sizeof(Vec5f));
#else // text
s << i << " " << j << " ";
s << e[0] << " " << e[1] << " " << e[2] << " " << e[3] << " " << e[4] << endl;
#endif
}
}
s.close();
return true;
}
bool read2d(const char *fn, SparseMat &m)
{
ifstream s(fn, ios::out | ios::binary);
if (!s) return false;
int h=0,w=0;
#ifdef SPARSEBINARY
s.read((char*)&h,sizeof(int));
s.read((char*)&w,sizeof(int));
#else
s >> h >> w;
#endif
int sz[] = {h,w};
m = SparseMat(2,sz,CV_32FC(5));
while(!s.eof())
{
int i,j;
Vec5f e;
#ifdef SPARSEBINARY
s.read((char*)&i,sizeof(int));
s.read((char*)&j,sizeof(int));
s.read((char*)&e,sizeof(Vec5f));
#else
s >> i >> j >> e[0] >> e[1] >> e[2] >> e[3] >> e[4];
#endif
if (e == Vec5f::zeros()) // weird..
break;
m.ref<Vec5f>(i,j) = e;
}
s.close();
return true;
}
int main(int argc, char **argv)
{
int sz[] = {10,10};
SparseMat m(2,sz,CV_32FC(5));
m.ref<Vec5f>(2,2) = Vec5f(1,2,3,4,5);
m.ref<Vec5f>(4,7) = Vec5f(2.2,1.1,3,3,3);
m.ref<Vec5f>(7,3) = Vec5f(6,7,8.1,9,0);
write2d("my.xxx",m);
SparseMat m2;
read2d("my.xxx",m2);
cerr << m2.ref<Vec5f>(2,2) << endl;
cerr << m2.ref<Vec5f>(4,7) << endl;
cerr << m2.ref<Vec5f>(7,3) << endl;
cerr << m2.ref<Vec5f>(9,9) << endl; // does not exist
return 0;
}
just out of curiosity: what's inside your sparse mat ? (and how large is it?)