img_radon.h File Reference

#include "mg_processing.h"
#include "symmetry.h"
#include "rwimg.h"

Functions
Bimage *	img_radon_transform (Bimage *p, int type, int nkernel, int kernel_power, int padd, int ntheta)
	Calculates the Radon transform of an image. More...
Bimage *	img_radon_inverse_transform (Bimage *p, int type, int nkernel, int kernel_power, int padd)
	Calculates a 3D image from a Radon transform. More...
int	img_radon_pocs_filter (Bimage *p, int n_cyc_out, int n_cyc_in, double rad_3D, double rad_plane, int support, Bimage *pmask)
	Filters a radon transform using the POCS method. More...
Bimage *	img_radon_reconstruction (Bproject *project, Bsymmetry &sym, Bstring &file_mask, int rec_size, int ntheta, int table_size, double threshold, Vector3< double > origin, int nkernel, int kernel_power)
	Reconstructs a Radon transform from a set of projections. More...
int	img_resize_to_next_power2 (Bimage *p, int fill_type, double fill)
	Resizes without interpolation or rescaling to the next power of 2. More...

Function Documentation

img_radon_inverse_transform()

Bimage * img_radon_inverse_transform	(	Bimage *	p,
		int	type,
		int	nkernel,
		int	kernel_power,
		int	padd
	)

Calculates a 3D image from a Radon transform.

Parameters

*p	radon transform to be back-transformed.
type	type of transformation.
nkernel	kernel size.
kernel_power	kernel exponent (usually 2).
padd	padding flag (0=no padding, 1=padding twofold).

Returns

Bimage* transformed image.

Type:
1 = From single axis proj. to 3D structure, output is a 3D image with size (z,z,z)
2 = From quarter radon transform to single axis proj., output is a gallery of ntheta 2D image with size (z,z)
3 = From full radon transform to 3D structure, output is a 3D image with size (z,z,z)
4 = From quarter radon transform to 3D structure, output is a 3D image with size (z,z,z)

img_radon_pocs_filter()

int img_radon_pocs_filter	(	Bimage *	p,
		int	n_cyc_out,
		int	n_cyc_in,
		double	rad_3D,
		double	rad_plane,
		int	support,
		Bimage *	pmask
	)

Filters a radon transform using the POCS method.

Parameters

*p	radon transform.
n_cyc_out	outer cycles, swapping r,phi and r,theta planes
n_cyc_in	inner cycles, within r,phi and r,theta planes
rad_3D	limiting radius in 3D.
rad_plane	limiting radius in plane.
support	flag to impose finiteness in real space.
*pmask	mask of dimension (ntheta/2,ntheta/2).

Returns

Bimage* transformed image.

Filters a Radon transform to impose consistency and/or to fill holes.
It can be used in two ways:
a) When the Radon transform is not completely filled, it fills the holes
    described in the mask file produced by proj_to_radon.
b) When the Radon transform is filled and noisy, it impose consistency.
The mask must have the same dimensions as a plane in the radon transform.

img_radon_reconstruction()

Bimage * img_radon_reconstruction	(	Bproject *	project,
		Bsymmetry &	sym,
		Bstring &	file_mask,
		int	rec_size,
		int	ntheta,
		int	table_size,
		double	threshold,
		Vector3< double >	origin,
		int	nkernel,
		int	kernel_power
	)

Reconstructs a Radon transform from a set of projections.

Parameters

*project	image processing parameter structure.
&sym	point group symmetry.
&file_mask	output file name of mask of dimension (ntheta,ntheta).
rec_size	reconstruction size (x,y,z)
ntheta	number of angles in the 2*PI range.
table_size	lookup table size.
threshold	threshold for rejecting images.
origin	origin reference for shifts.
nkernel	kernel size.
kernel_power	kernel exponent (usually 2).

Returns

Bimage* transformed image.

The parameters are defined in the hierarchical project structure.
The radon transform of each image is calculated and all its 
symmetry-related views are written into the reconstruction volume.
A mask image is calculated for the angular coverage of orientation
space and used to weigh the reconstruction.

img_radon_transform()

Bimage * img_radon_transform	(	Bimage *	p,
		int	type,
		int	nkernel,
		int	kernel_power,
		int	padd,
		int	ntheta
	)

Calculates the Radon transform of an image.

Parameters

*p	image to be transformed.
type	type of transformation.
nkernel	kernel size.
kernel_power	kernel exponent (usually 2).
padd	padding flag (0=no padding, 1=padding twofold).
ntheta	number of angles in the 2*PI range.

Returns

Bimage* transformed image.

Computes the Radon transform of a 3D image with all sides equal
(a cube) and a power of 2. The transform is calculated in spherical
coordinates where ntheta is the number of sampling points in the 
range 0 - 2*PI along the two angular axes. Because half of this 
range is redundant (0-PI is enough), a smaller output can be 
generated.
    Type:
1 = From 3D structure to single axis proj., output is a gallery of ntheta 2D image with size (x,x)
2 = From single axis proj. to quarter radon transform, output is a 3D image with size (x,ntheta/2,ntheta/2)
3 = From 3D structure to full radon transform, output is a 3D image with size (x,ntheta,ntheta)
4 = From 3D structure to quarter radon transform, output is a 3D image with size (x,ntheta/2,ntheta/2)

img_resize_to_next_power2()

int img_resize_to_next_power2	(	Bimage *	p,
		int	fill_type,
		double	fill
	)

Resizes without interpolation or rescaling to the next power of 2.

Parameters

p	image (modified).
fill_type	FILL_AVERAGE, FILL_BACKGROUND, FILL_USER
fill	value to fill in new regions.

Returns

int 0.

An image is resized to the next power of two in each dimension
greater than 1 with translation and filling of new regions with 
a given value.
The new data replaces the old data.