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EMAN::FFTResampleProcessor Class Reference

FFTResampleProcessor resamples an image by clipping the Fourier Transform This is the same as multipyling the FT by a box window, in real space this is a convolution that will induce rippling. More...

#include <processor.h>

Inheritance diagram for EMAN::FFTResampleProcessor:

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Collaboration diagram for EMAN::FFTResampleProcessor:

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List of all members.

Public Member Functions

virtual EMDataprocess (const EMData *const image)
 To proccess an image out-of-place.
virtual void process_inplace (EMData *image)
 To process an image in-place.
string get_desc () const
 Get the descrition of this specific processor.
string get_name () const
 Get the processor's name.
TypeDict get_param_types () const
 Get processor parameter information in a dictionary.

Static Public Member Functions

ProcessorNEW ()

Static Public Attributes

const string NAME = "math.fft.resample"

Private Member Functions

void fft_resample (EMData *to, const EMData *const from, const float &sample_rate)
 An internal function that encapsulates a routine common to both process and process inplace.

Detailed Description

FFTResampleProcessor resamples an image by clipping the Fourier Transform This is the same as multipyling the FT by a box window, in real space this is a convolution that will induce rippling.

Hence it should probably be combined with a damping function near the edge Works for even/odd, 1D, 2D and 3D images (completely robust, tested)

Author:
David Woolford
Date:
June 2009
Parameters:
n sampe_rate

Definition at line 3587 of file processor.h.


Member Function Documentation

void FFTResampleProcessor::fft_resample EMData to,
const EMData *const   from,
const float &  sample_rate
[private]
 

An internal function that encapsulates a routine common to both process and process inplace.

Parameters:
to the smaller image that will store the shrunken values
from the larger image that will be used to calculate the shrunken values
shrinkfactor the shrink amount

Definition at line 2130 of file processor.cpp.

References EMAN::EMData::clip_inplace(), EMAN::EMData::depad_corner(), EMAN::EMData::do_fft_inplace(), EMAN::EMData::do_ift_inplace(), EMAN::EMData::get_ndim(), EMAN::EMData::get_xsize(), EMAN::EMData::get_ysize(), EMAN::EMData::get_zsize(), EMAN::EMData::is_complex(), nx, ny, EMAN::EMData::process_inplace(), EMAN::EMData::set_fftodd(), and UnexpectedBehaviorException.

Referenced by process(), and process_inplace().

02130                                                                                                       {
02131         int nx = from->get_xsize();
02132         int ny = from->get_ysize();
02133         int nz = from->get_zsize();
02134 
02135         int new_nx = static_cast<int>( static_cast<float> (nx) / sample_rate);
02136         int new_ny = static_cast<int>( static_cast<float> (ny) / sample_rate);
02137         int new_nz = static_cast<int>( static_cast<float> (nz) / sample_rate);
02138 
02139         if (new_nx == 0) throw UnexpectedBehaviorException("The resample rate causes the pixel dimensions in the x direction to go to zero");
02140         if (new_ny == 0) new_ny = 1;
02141         if (new_nz == 0) new_nz = 1;
02142 
02143         int ndim = from->get_ndim();
02144         if ( ndim < 3 ) {
02145                 new_nz = 1;
02146         }
02147         if ( ndim < 2 ) {
02148                 new_ny = 1;
02149         }
02150 
02151         int fft_x_correction = 1;
02152         if (new_nx % 2 == 0) fft_x_correction = 2;
02153 
02154         int fft_y_correction = 0;
02155         if (ny != 1 && new_ny % 2 == 0 && ny % 2 == 1) fft_y_correction = 1;
02156         else if (ny != 1 && new_ny % 2 == 1 && ny % 2 == 0) fft_y_correction = -1;
02157 
02158         int fft_z_correction = 0;
02159         if (nz != 1 && new_nz % 2 == 0 && nz % 2 == 1) fft_z_correction = 1;
02160         else if (nz != 1 && new_nz % 2 == 1 && nz % 2 == 0) fft_z_correction = -1;
02161 
02162         if ( ! to->is_complex()) to->do_fft_inplace();
02163 
02164         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocenter");
02165 
02166         Region clip(0,(ny-new_ny)/2-fft_y_correction,(nz-new_nz)/2-fft_z_correction,new_nx+fft_x_correction,new_ny,new_nz);
02167         to->clip_inplace(clip);
02168 
02169         if (fft_x_correction == 1) to->set_fftodd(true);
02170         else to->set_fftodd(false);
02171 
02172         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocorner");
02173 
02174         to->do_ift_inplace();
02175         to->depad_corner();
02176 
02177 }

string EMAN::FFTResampleProcessor::get_desc  )  const [inline, virtual]
 

Get the descrition of this specific processor.

This function must be overwritten by a subclass.

Returns:
The description of this processor.

Implements EMAN::Processor.

Definition at line 3594 of file processor.h.

03595                         {
03596                                 return "Robust resampling of an image by clipping its Fourier transform.";
03597                         }

string EMAN::FFTResampleProcessor::get_name  )  const [inline, virtual]
 

Get the processor's name.

Each processor is identified by a unique name.

Returns:
The processor's name.

Implements EMAN::Processor.

Definition at line 3599 of file processor.h.

03600                         {
03601                                 return NAME;
03602                         }

TypeDict EMAN::FFTResampleProcessor::get_param_types  )  const [inline, virtual]
 

Get processor parameter information in a dictionary.

Each parameter has one record in the dictionary. Each record contains its name, data-type, and description.

Returns:
A dictionary containing the parameter info.

Reimplemented from EMAN::Processor.

Definition at line 3608 of file processor.h.

References EMAN::TypeDict::put().

03609                         {
03610                                 TypeDict d;
03611                                 d.put("n", EMObject::FLOAT, "The sample rate. Less than one enlarges the image, greater than one shrinks it.");
03612                                 return d;
03613                         }

Processor* EMAN::FFTResampleProcessor::NEW  )  [inline, static]
 

Definition at line 3603 of file processor.h.

03604                         {
03605                                 return new FFTResampleProcessor();
03606                         }

EMData * FFTResampleProcessor::process const EMData *const   image  )  [virtual]
 

To proccess an image out-of-place.

For those processors which can only be processed out-of-place, override this function to give the right behavior.

Parameters:
image The image will be copied, actual process happen on copy of image.
Returns:
the image processing result, may or may not be the same size of the input image

Reimplemented from EMAN::Processor.

Definition at line 2095 of file processor.cpp.

References EMAN::EMData::copy(), EMAN::EMData::do_fft(), fft_resample(), InvalidValueException, EMAN::EMData::is_complex(), EMAN::EMData::scale_pixel(), EMAN::Dict::set_default(), and EMAN::EMData::update().

02096 {
02097         float sample_rate = params.set_default("n",0.0f);
02098         if (sample_rate <= 0.0F  )  {
02099                 throw InvalidValueException(sample_rate,        "sample rate must be >0 ");
02100         }
02101 
02102         EMData* result;
02103         if (image->is_complex()) result = image->copy();
02104         else result = image->do_fft();
02105         fft_resample(result,image,sample_rate);
02106         // The image may have been padded - we should shift it so that the phase origin is where FFTW expects it
02107         result->update();
02108         result->scale_pixel(sample_rate);
02109         return result;
02110 }

void FFTResampleProcessor::process_inplace EMData image  )  [virtual]
 

To process an image in-place.

For those processors which can only be processed out-of-place, override this function to just print out some error message to remind user call the out-of-place version.

Parameters:
image The image to be processed.

Implements EMAN::Processor.

Definition at line 2112 of file processor.cpp.

References fft_resample(), ImageFormatException, InvalidValueException, EMAN::EMData::is_complex(), EMAN::EMData::scale_pixel(), EMAN::Dict::set_default(), and EMAN::EMData::update().

02113 {
02114         if (image->is_complex()) throw ImageFormatException("Error, the fft resampling processor does not work on complex images");
02115 
02116 
02117         float sample_rate = params.set_default("n",0.0f);
02118         if (sample_rate <= 0.0F  )  {
02119                 throw InvalidValueException(sample_rate,        "sample rate (n) must be >0 ");
02120         }
02121 
02122         fft_resample(image,image,sample_rate);
02123 
02124         image->scale_pixel(sample_rate);
02125         image->update();
02126 
02127 
02128 }


Member Data Documentation

const string FFTResampleProcessor::NAME = "math.fft.resample" [static]
 

Definition at line 128 of file processor.cpp.


The documentation for this class was generated from the following files:
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