convert big yml data - ios

Question

There is any other way/trick to store the depth map in the database? Basically, we are trying to store 300000 double values. If it helps we can convert the array into a NSMutableArray or similar so that we can serialize it. I don’t know yet how to do it. I tried to find a way to convert it to a binary file instead of ASCII but no luck yet.

Answer 1

You can save a lot of memory by storing the raw binary data in a BLOB.
If you don't have fixed rows and cols of your matrix, you can put at the beginning of the file two integers for rows and cols.
I'll add a simple example on how to save and load the data of matrix, preceded by rows and cols.
#include <opencv2/opencv.hpp>
#include <fstream>
using namespace cv;
using namespace std;
int main()
{
Mat1d m = (Mat1d(3, 3) << 1, 2, 3, 4, 5, 6, 7, 8, 9);
Mat1d n;
{
ofstream ofs("test.bin", fstream::binary);
ofs.write((char*)&m.rows, sizeof(int)); // Save rows
ofs.write((char*)&m.cols, sizeof(int)); // Save cols
ofs.write((char*)m.data, m.total()*sizeof(double)); // Save data
}
{
ifstream ifs("test.bin", fstream::binary);
int rows, cols;
ifs.read((char*)&rows, sizeof(int)); // Load rows
ifs.read((char*)&cols, sizeof(int)); // Load cols
n = Mat1d(rows, cols); // Resize the matrix according to rows, cols
ifs.read((char*)n.data, rows*cols*sizeof(double)); // Load data
}
// Now m and n are equal
return 0;
}
If you need further compression you can read and write the stream using gzstream