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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 3585 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 2128 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().

02128                                                                                                       {
02129         int nx = from->get_xsize();
02130         int ny = from->get_ysize();
02131         int nz = from->get_zsize();
02132 
02133         int new_nx = static_cast<int>( static_cast<float> (nx) / sample_rate);
02134         int new_ny = static_cast<int>( static_cast<float> (ny) / sample_rate);
02135         int new_nz = static_cast<int>( static_cast<float> (nz) / sample_rate);
02136 
02137         if (new_nx == 0) throw UnexpectedBehaviorException("The resample rate causes the pixel dimensions in the x direction to go to zero");
02138         if (new_ny == 0) new_ny = 1;
02139         if (new_nz == 0) new_nz = 1;
02140 
02141         int ndim = from->get_ndim();
02142         if ( ndim < 3 ) {
02143                 new_nz = 1;
02144         }
02145         if ( ndim < 2 ) {
02146                 new_ny = 1;
02147         }
02148 
02149         int fft_x_correction = 1;
02150         if (new_nx % 2 == 0) fft_x_correction = 2;
02151 
02152         int fft_y_correction = 0;
02153         if (ny != 1 && new_ny % 2 == 0 && ny % 2 == 1) fft_y_correction = 1;
02154         else if (ny != 1 && new_ny % 2 == 1 && ny % 2 == 0) fft_y_correction = -1;
02155 
02156         int fft_z_correction = 0;
02157         if (nz != 1 && new_nz % 2 == 0 && nz % 2 == 1) fft_z_correction = 1;
02158         else if (nz != 1 && new_nz % 2 == 1 && nz % 2 == 0) fft_z_correction = -1;
02159 
02160         if ( ! to->is_complex()) to->do_fft_inplace();
02161 
02162         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocenter");
02163 
02164         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);
02165         to->clip_inplace(clip);
02166 
02167         if (fft_x_correction == 1) to->set_fftodd(true);
02168         else to->set_fftodd(false);
02169 
02170         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocorner");
02171 
02172         to->do_ift_inplace();
02173         to->depad_corner();
02174 
02175 }

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 3592 of file processor.h.

03593                         {
03594                                 return "Robust resampling of an image by clipping its Fourier transform.";
03595                         }

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 3597 of file processor.h.

03598                         {
03599                                 return NAME;
03600                         }

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 3606 of file processor.h.

References EMAN::TypeDict::put().

03607                         {
03608                                 TypeDict d;
03609                                 d.put("n", EMObject::FLOAT, "The sample rate. Less than one enlarges the image, greater than one shrinks it.");
03610                                 return d;
03611                         }

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

Definition at line 3601 of file processor.h.

03602                         {
03603                                 return new FFTResampleProcessor();
03604                         }

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 2093 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().

02094 {
02095         float sample_rate = params.set_default("n",0.0f);
02096         if (sample_rate <= 0.0F  )  {
02097                 throw InvalidValueException(sample_rate,        "sample rate must be >0 ");
02098         }
02099 
02100         EMData* result;
02101         if (image->is_complex()) result = image->copy();
02102         else result = image->do_fft();
02103         fft_resample(result,image,sample_rate);
02104         // The image may have been padded - we should shift it so that the phase origin is where FFTW expects it
02105         result->update();
02106         result->scale_pixel(sample_rate);
02107         return result;
02108 }

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 2110 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().

02111 {
02112         if (image->is_complex()) throw ImageFormatException("Error, the fft resampling processor does not work on complex images");
02113 
02114 
02115         float sample_rate = params.set_default("n",0.0f);
02116         if (sample_rate <= 0.0F  )  {
02117                 throw InvalidValueException(sample_rate,        "sample rate (n) must be >0 ");
02118         }
02119 
02120         fft_resample(image,image,sample_rate);
02121 
02122         image->scale_pixel(sample_rate);
02123         image->update();
02124 
02125 
02126 }


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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