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

static ProcessorNEW ()

Static Public Attributes

static 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 2124 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(), EMAN::EMData::process_inplace(), EMAN::EMData::set_fftodd(), and UnexpectedBehaviorException.

Referenced by process(), and process_inplace().

02124                                                                                                       {
02125         int nx = from->get_xsize();
02126         int ny = from->get_ysize();
02127         int nz = from->get_zsize();
02128 
02129         int new_nx = static_cast<int>( static_cast<float> (nx) / sample_rate);
02130         int new_ny = static_cast<int>( static_cast<float> (ny) / sample_rate);
02131         int new_nz = static_cast<int>( static_cast<float> (nz) / sample_rate);
02132 
02133         if (new_nx == 0) throw UnexpectedBehaviorException("The resample rate causes the pixel dimensions in the x direction to go to zero");
02134         if (new_ny == 0) new_ny = 1;
02135         if (new_nz == 0) new_nz = 1;
02136 
02137         int ndim = from->get_ndim();
02138         if ( ndim < 3 ) {
02139                 new_nz = 1;
02140         }
02141         if ( ndim < 2 ) {
02142                 new_ny = 1;
02143         }
02144 
02145         int fft_x_correction = 1;
02146         if (new_nx % 2 == 0) fft_x_correction = 2;
02147 
02148         int fft_y_correction = 0;
02149         if (ny != 1 && new_ny % 2 == 0 && ny % 2 == 1) fft_y_correction = 1;
02150         else if (ny != 1 && new_ny % 2 == 1 && ny % 2 == 0) fft_y_correction = -1;
02151 
02152         int fft_z_correction = 0;
02153         if (nz != 1 && new_nz % 2 == 0 && nz % 2 == 1) fft_z_correction = 1;
02154         else if (nz != 1 && new_nz % 2 == 1 && nz % 2 == 0) fft_z_correction = -1;
02155 
02156         if ( ! to->is_complex()) to->do_fft_inplace();
02157 
02158         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocenter");
02159 
02160         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);
02161         to->clip_inplace(clip);
02162 
02163         if (fft_x_correction == 1) to->set_fftodd(true);
02164         else to->set_fftodd(false);
02165 
02166         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocorner");
02167 
02168         to->do_ift_inplace();
02169         to->depad_corner();
02170 
02171 }

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.

References NAME.

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::EMObject::FLOAT, and 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                         }

static 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 2089 of file processor.cpp.

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

02090 {
02091         float sample_rate = params.set_default("n",0.0f);
02092         if (sample_rate <= 0.0F  )  {
02093                 throw InvalidValueException(sample_rate,        "sample rate must be >0 ");
02094         }
02095 
02096         EMData* result;
02097         if (image->is_complex()) result = image->copy();
02098         else result = image->do_fft();
02099         fft_resample(result,image,sample_rate);
02100         // The image may have been padded - we should shift it so that the phase origin is where FFTW expects it
02101         result->update();
02102         result->scale_pixel(sample_rate);
02103         return result;
02104 }

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 2106 of file processor.cpp.

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

02107 {
02108         if (image->is_complex()) throw ImageFormatException("Error, the fft resampling processor does not work on complex images");
02109 
02110 
02111         float sample_rate = params.set_default("n",0.0f);
02112         if (sample_rate <= 0.0F  )  {
02113                 throw InvalidValueException(sample_rate,        "sample rate (n) must be >0 ");
02114         }
02115 
02116         fft_resample(image,image,sample_rate);
02117 
02118         image->scale_pixel(sample_rate);
02119         image->update();
02120 
02121 
02122 }


Member Data Documentation

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

Definition at line 3613 of file processor.h.

Referenced by get_name().


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