fs::MghHeader Struct Reference

Models the header of an MGH file. More...

#include <libfs.h>

Collaboration diagram for fs::MghHeader:

Public Member Functions
	MghHeader ()
	Empty default constuctor.
	MghHeader (Curv curv)
	MghHeader (std::vector< float > curv_data)
size_t	num_values () const
	Compute the number of values based on the dim*length header fields.
std::vector< float >	compute_vox2ras () const
	Compute the 4x4 voxel-to-RAS (vox2ras) matrix from the RAS header fields, if available.

Public Attributes
int32_t	dim1length = 0
	size of data along 1st dimension
int32_t	dim2length = 0
	size of data along 2nd dimension
int32_t	dim3length = 0
	size of data along 3rd dimension
int32_t	dim4length = 0
	size of data along 4th dimension
int32_t	dtype = 0
	the MRI data type
int32_t	dof = 0
	typically ignored
int16_t	ras_good_flag = 0
	flag indicating whether the data in the RAS fields (Mdc, Pxyz_c) are valid. 1 means valid, everything else means invalid.
float	xsize = 0.0
	size of voxels along 1st axis (x or r)
float	ysize = 0.0
	size of voxels along 2nd axis (y or a)
float	zsize = 0.0
	size of voxels along 3rd axis (z or s)
std::vector< float >	Mdc
	matrix
std::vector< float >	Pxyz_c
	x,y,z coordinates of central vertex

Detailed Description

Models the header of an MGH file.

Constructor & Destructor Documentation

MghHeader() [1/2]

fs::MghHeader::MghHeader ( Curv  curv )

inline

< Constuctor to fill header from a Curv instance.

MghHeader() [2/2]

fs::MghHeader::MghHeader ( std::vector< float >  curv_data )

inline

< Constuctor to fill header from a 1D float array (curv data).

Member Function Documentation

compute_vox2ras()

std::vector< float > fs::MghHeader::compute_vox2ras ( ) const

inline

Compute the 4x4 voxel-to-RAS (vox2ras) matrix from the RAS header fields, if available.

The vox2ras matrix maps voxel indices to world (RAS) coordinates: the world coordinate of a voxel (i, j, k) is vox2ras * [i, j, k, 1]. The linear part (upper left 3x3 block) maps a unit step along voxel axis j to a world displacement of size_j * Mdc_row_j, i.e. column j is scaled by the voxel size of axis j. This is the FreeSurfer convention (vox2ras = Mdc^T * diag(size), with the rows of the MGH Mdc matrix being the unit direction cosines of the 3 volume axes). The translation is the RAS coordinate of voxel (0,0,0), derived from the center voxel Pxyz_c stored in the header (center index uses integer division dim/2).

Returns

the vox2ras matrix as 16 floats in row-major order (entry [i*4+j] = row i, col j), or an empty vector if the header does not carry valid RAS information.

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The documentation for this struct was generated from the following file:

• include/libfs.h