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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 3506 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 2089 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().

02089                                                                                                       {
02090         int nx = from->get_xsize();
02091         int ny = from->get_ysize();
02092         int nz = from->get_zsize();
02093 
02094         int new_nx = static_cast<int>( static_cast<float> (nx) / sample_rate);
02095         int new_ny = static_cast<int>( static_cast<float> (ny) / sample_rate);
02096         int new_nz = static_cast<int>( static_cast<float> (nz) / sample_rate);
02097 
02098         if (new_nx == 0) throw UnexpectedBehaviorException("The resample rate causes the pixel dimensions in the x direction to go to zero");
02099         if (new_ny == 0) new_ny = 1;
02100         if (new_nz == 0) new_nz = 1;
02101 
02102         int ndim = from->get_ndim();
02103         if ( ndim < 3 ) {
02104                 new_nz = 1;
02105         }
02106         if ( ndim < 2 ) {
02107                 new_ny = 1;
02108         }
02109 
02110         int fft_x_correction = 1;
02111         if (new_nx % 2 == 0) fft_x_correction = 2;
02112 
02113         int fft_y_correction = 0;
02114         if (ny != 1 && new_ny % 2 == 0 && ny % 2 == 1) fft_y_correction = 1;
02115         else if (ny != 1 && new_ny % 2 == 1 && ny % 2 == 0) fft_y_correction = -1;
02116 
02117         int fft_z_correction = 0;
02118         if (nz != 1 && new_nz % 2 == 0 && nz % 2 == 1) fft_z_correction = 1;
02119         else if (nz != 1 && new_nz % 2 == 1 && nz % 2 == 0) fft_z_correction = -1;
02120 
02121         if ( ! to->is_complex()) to->do_fft_inplace();
02122 
02123         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocenter");
02124 
02125         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);
02126         to->clip_inplace(clip);
02127 
02128         if (fft_x_correction == 1) to->set_fftodd(true);
02129         else to->set_fftodd(false);
02130 
02131         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocorner");
02132 
02133         to->do_ift_inplace();
02134         to->depad_corner();
02135 
02136 }

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 3513 of file processor.h.

03514                         {
03515                                 return "Robust resampling of an image by clipping its Fourier transform.";
03516                         }

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 3518 of file processor.h.

03519                         {
03520                                 return NAME;
03521                         }

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 3527 of file processor.h.

References EMAN::TypeDict::put().

03528                         {
03529                                 TypeDict d;
03530                                 d.put("n", EMObject::FLOAT, "The sample rate. Less than one enlarges the image, greater than one shrinks it.");
03531                                 return d;
03532                         }

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

Definition at line 3522 of file processor.h.

03523                         {
03524                                 return new FFTResampleProcessor();
03525                         }

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 2054 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().

02055 {
02056         float sample_rate = params.set_default("n",0.0f);
02057         if (sample_rate <= 0.0F  )  {
02058                 throw InvalidValueException(sample_rate,        "sample rate must be >0 ");
02059         }
02060 
02061         EMData* result;
02062         if (image->is_complex()) result = image->copy();
02063         else result = image->do_fft();
02064         fft_resample(result,image,sample_rate);
02065         // The image may have been padded - we should shift it so that the phase origin is where FFTW expects it
02066         result->update();
02067         result->scale_pixel(sample_rate);
02068         return result;
02069 }

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 2071 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().

02072 {
02073         if (image->is_complex()) throw ImageFormatException("Error, the fft resampling processor does not work on complex images");
02074 
02075 
02076         float sample_rate = params.set_default("n",0.0f);
02077         if (sample_rate <= 0.0F  )  {
02078                 throw InvalidValueException(sample_rate,        "sample rate (n) must be >0 ");
02079         }
02080 
02081         fft_resample(image,image,sample_rate);
02082 
02083         image->scale_pixel(sample_rate);
02084         image->update();
02085 
02086 
02087 }


Member Data Documentation

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

Definition at line 127 of file processor.cpp.


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