Field data

This is the native binary format of DisPerSE. Functions for reading and writing NDfield format in C can be found within the file ${DISPERSE_SRC}/src/C/NDfield.c (see functions Load_NDfield and Save_NDfield).

When using the C functions from Disperse, data is loaded into the following C structure which is close to the actual structure of the file (see file ${DISPERSE_SRC}/src/C/NDfield.h):

#define ND_CHAR   (1<<0)
#define ND_UCHAR  (1<<1)
#define ND_SHORT  (1<<2)
#define ND_USHORT (1<<3)
#define ND_INT    (1<<4)
#define ND_UINT   (1<<5)
#define ND_LONG   (1<<6)
#define ND_ULONG  (1<<7)
#define ND_FLOAT  (1<<8)
#define ND_DOUBLE (1<<9)

typedef struct NDfield_str
{
 char comment[80];  // a comment on the data
 int dims[NDFIELD_MAX_DIMS];  // dimensions of the grid, must be [ndims,nparticles] when data represents sample particles coordinates (i.e. when fdims_index!=0)
 int ndims;  // number of dimensions of the space
 int n_dims;  // number of meaningfull values in dims array
 int fdims_index; // if 0, the field is a regular grid of dimensions dims, else the file contains the dims[0] coordinates of dims[1] particles.
 int datatype;  // type of the data (one of the ND_... defined above)
 double x0[NDFIELD_MAX_DIMS];  // origin of the bounding box
 double delta[NDFIELD_MAX_DIMS];  // extent of the bounding box
 char dummy[160];  // dummy data, for future extensions or for storing anything you want.

 void *val;  // pointer to data

 long nval;  // total number of particles (fdims_index==1) or pixels (fdims_index==0)
 int datasize;  // size in bytes of datatype type.
} NDfield;

The NDfield binary format is organized as follows (blocks are delimited by dummy variables indicating the size of the blocks for FORTRAN compatibility, but they are ignored in C):

This field format is used to read 2D or 3D regular grids of arbitrary dimensions in the popular Flexible Image Transport System (FITS) image format. A popular library for reading and writing FITS image in C or FORTRAN is CFITSIO, which must be installed for DisPerSE to be able to use this kind of files.

This file format is also used for storing HEALPIX tesselations of the sphere. DisPerSE will automatically detect if the FITS file contains a HEALPIX tesselation.

This input format is used to read 2D regular grids encoded in a popular picture format readable by SDL-image library (jpg, png, gif, ...). When using this format as input to mse, the field whose topology is computed is the luminosity L of the image, a weighted average of the RED, GREEN and BLUE components of the image:

L = 0.2989*RED + 0.5870*GREEN + 0.1140*BLUE