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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 3544 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 2117 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().

02117                                                                                                       {
02118         int nx = from->get_xsize();
02119         int ny = from->get_ysize();
02120         int nz = from->get_zsize();
02121 
02122         int new_nx = static_cast<int>( static_cast<float> (nx) / sample_rate);
02123         int new_ny = static_cast<int>( static_cast<float> (ny) / sample_rate);
02124         int new_nz = static_cast<int>( static_cast<float> (nz) / sample_rate);
02125 
02126         if (new_nx == 0) throw UnexpectedBehaviorException("The resample rate causes the pixel dimensions in the x direction to go to zero");
02127         if (new_ny == 0) new_ny = 1;
02128         if (new_nz == 0) new_nz = 1;
02129 
02130         int ndim = from->get_ndim();
02131         if ( ndim < 3 ) {
02132                 new_nz = 1;
02133         }
02134         if ( ndim < 2 ) {
02135                 new_ny = 1;
02136         }
02137 
02138         int fft_x_correction = 1;
02139         if (new_nx % 2 == 0) fft_x_correction = 2;
02140 
02141         int fft_y_correction = 0;
02142         if (ny != 1 && new_ny % 2 == 0 && ny % 2 == 1) fft_y_correction = 1;
02143         else if (ny != 1 && new_ny % 2 == 1 && ny % 2 == 0) fft_y_correction = -1;
02144 
02145         int fft_z_correction = 0;
02146         if (nz != 1 && new_nz % 2 == 0 && nz % 2 == 1) fft_z_correction = 1;
02147         else if (nz != 1 && new_nz % 2 == 1 && nz % 2 == 0) fft_z_correction = -1;
02148 
02149         if ( ! to->is_complex()) to->do_fft_inplace();
02150 
02151         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocenter");
02152 
02153         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);
02154         to->clip_inplace(clip);
02155 
02156         if (fft_x_correction == 1) to->set_fftodd(true);
02157         else to->set_fftodd(false);
02158 
02159         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocorner");
02160 
02161         to->do_ift_inplace();
02162         to->depad_corner();
02163 
02164 }

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 3551 of file processor.h.

03552                         {
03553                                 return "Robust resampling of an image by clipping its Fourier transform.";
03554                         }

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 3556 of file processor.h.

03557                         {
03558                                 return NAME;
03559                         }

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 3565 of file processor.h.

References EMAN::TypeDict::put().

03566                         {
03567                                 TypeDict d;
03568                                 d.put("n", EMObject::FLOAT, "The sample rate. Less than one enlarges the image, greater than one shrinks it.");
03569                                 return d;
03570                         }

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

Definition at line 3560 of file processor.h.

03561                         {
03562                                 return new FFTResampleProcessor();
03563                         }

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 2082 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().

02083 {
02084         float sample_rate = params.set_default("n",0.0f);
02085         if (sample_rate <= 0.0F  )  {
02086                 throw InvalidValueException(sample_rate,        "sample rate must be >0 ");
02087         }
02088 
02089         EMData* result;
02090         if (image->is_complex()) result = image->copy();
02091         else result = image->do_fft();
02092         fft_resample(result,image,sample_rate);
02093         // The image may have been padded - we should shift it so that the phase origin is where FFTW expects it
02094         result->update();
02095         result->scale_pixel(sample_rate);
02096         return result;
02097 }

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 2099 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().

02100 {
02101         if (image->is_complex()) throw ImageFormatException("Error, the fft resampling processor does not work on complex images");
02102 
02103 
02104         float sample_rate = params.set_default("n",0.0f);
02105         if (sample_rate <= 0.0F  )  {
02106                 throw InvalidValueException(sample_rate,        "sample rate (n) must be >0 ");
02107         }
02108 
02109         fft_resample(image,image,sample_rate);
02110 
02111         image->scale_pixel(sample_rate);
02112         image->update();
02113 
02114 
02115 }


Member Data Documentation

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

Definition at line 133 of file processor.cpp.


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