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 3581 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 2149 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().

02149                                                                                                       {
02150         int nx = from->get_xsize();
02151         int ny = from->get_ysize();
02152         int nz = from->get_zsize();
02153 
02154         int new_nx = static_cast<int>( static_cast<float> (nx) / sample_rate);
02155         int new_ny = static_cast<int>( static_cast<float> (ny) / sample_rate);
02156         int new_nz = static_cast<int>( static_cast<float> (nz) / sample_rate);
02157 
02158         if (new_nx == 0) throw UnexpectedBehaviorException("The resample rate causes the pixel dimensions in the x direction to go to zero");
02159         if (new_ny == 0) new_ny = 1;
02160         if (new_nz == 0) new_nz = 1;
02161 
02162         int ndim = from->get_ndim();
02163         if ( ndim < 3 ) {
02164                 new_nz = 1;
02165         }
02166         if ( ndim < 2 ) {
02167                 new_ny = 1;
02168         }
02169 
02170         int fft_x_correction = 1;
02171         if (new_nx % 2 == 0) fft_x_correction = 2;
02172 
02173         int fft_y_correction = 0;
02174         if (ny != 1 && new_ny % 2 == 0 && ny % 2 == 1) fft_y_correction = 1;
02175         else if (ny != 1 && new_ny % 2 == 1 && ny % 2 == 0) fft_y_correction = -1;
02176 
02177         int fft_z_correction = 0;
02178         if (nz != 1 && new_nz % 2 == 0 && nz % 2 == 1) fft_z_correction = 1;
02179         else if (nz != 1 && new_nz % 2 == 1 && nz % 2 == 0) fft_z_correction = -1;
02180 
02181         if ( ! to->is_complex()) to->do_fft_inplace();
02182 
02183         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocenter");
02184 
02185         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);
02186         to->clip_inplace(clip);
02187 
02188         if (fft_x_correction == 1) to->set_fftodd(true);
02189         else to->set_fftodd(false);
02190 
02191         if (ndim != 1) to->process_inplace("xform.fourierorigin.tocorner");
02192 
02193         to->do_ift_inplace();
02194         to->depad_corner();
02195 
02196 }

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 3588 of file processor.h.

03589                         {
03590                                 return "Robust resampling of an image by clipping its Fourier transform.";
03591                         }

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 3593 of file processor.h.

References NAME.

03594                         {
03595                                 return NAME;
03596                         }

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 3602 of file processor.h.

References EMAN::EMObject::FLOAT, and EMAN::TypeDict::put().

03603                         {
03604                                 TypeDict d;
03605                                 d.put("n", EMObject::FLOAT, "The sample rate. Less than one enlarges the image, greater than one shrinks it.");
03606                                 return d;
03607                         }

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

Definition at line 3597 of file processor.h.

03598                         {
03599                                 return new FFTResampleProcessor();
03600                         }

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 2114 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().

02115 {
02116         float sample_rate = params.set_default("n",0.0f);
02117         if (sample_rate <= 0.0F  )  {
02118                 throw InvalidValueException(sample_rate,        "sample rate must be >0 ");
02119         }
02120 
02121         EMData* result;
02122         if (image->is_complex()) result = image->copy();
02123         else result = image->do_fft();
02124         fft_resample(result,image,sample_rate);
02125         // The image may have been padded - we should shift it so that the phase origin is where FFTW expects it
02126         result->update();
02127         result->scale_pixel(sample_rate);
02128         return result;
02129 }

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 2131 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().

02132 {
02133         if (image->is_complex()) throw ImageFormatException("Error, the fft resampling processor does not work on complex images");
02134 
02135 
02136         float sample_rate = params.set_default("n",0.0f);
02137         if (sample_rate <= 0.0F  )  {
02138                 throw InvalidValueException(sample_rate,        "sample rate (n) must be >0 ");
02139         }
02140 
02141         fft_resample(image,image,sample_rate);
02142 
02143         image->scale_pixel(sample_rate);
02144         image->update();
02145 
02146 
02147 }


Member Data Documentation

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

Definition at line 3609 of file processor.h.

Referenced by get_name().


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