1 /*****************************************************************************
5 ** Purpose: Routines for signal-procesing filters
6 ** Progammer: Kevin Rosenberg
7 ** Date Started: Aug 1984
9 ** This is part of the CTSim program
10 ** Copyright (C) 1983-2000 Kevin Rosenberg
12 ** $Id: filter.cpp,v 1.23 2000/07/31 14:48:35 kevin Exp $
14 ** This program is free software; you can redistribute it and/or modify
15 ** it under the terms of the GNU General Public License (version 2) as
16 ** published by the Free Software Foundation.
18 ** This program is distributed in the hope that it will be useful,
19 ** but WITHOUT ANY WARRANTY; without even the implied warranty of
20 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 ** GNU General Public License for more details.
23 ** You should have received a copy of the GNU General Public License
24 ** along with this program; if not, write to the Free Software
25 ** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
26 ******************************************************************************/
30 int SignalFilter::N_INTEGRAL=500; //static member
32 const int SignalFilter::FILTER_INVALID = -1 ;
33 const int SignalFilter::FILTER_ABS_BANDLIMIT = 0; // filter times |x = |
34 const int SignalFilter::FILTER_ABS_SINC = 1;
35 const int SignalFilter::FILTER_ABS_G_HAMMING = 2;
36 const int SignalFilter::FILTER_ABS_COSINE = 3;
37 const int SignalFilter::FILTER_SHEPP = 4;
38 const int SignalFilter::FILTER_BANDLIMIT = 5;
39 const int SignalFilter::FILTER_SINC = 6;
40 const int SignalFilter::FILTER_G_HAMMING = 7;
41 const int SignalFilter::FILTER_COSINE = 8;
42 const int SignalFilter::FILTER_TRIANGLE = 9;
44 const char* SignalFilter::s_aszFilterName[] = {
57 const char* SignalFilter::s_aszFilterTitle[] = {
58 {"Abs(w) * Bandlimit"},
70 const int SignalFilter::s_iFilterCount = sizeof(s_aszFilterName) / sizeof(const char*);
72 const int SignalFilter::FILTER_METHOD_INVALID = -1;
73 const int SignalFilter::FILTER_METHOD_CONVOLUTION = 0;
74 const int SignalFilter::FILTER_METHOD_FOURIER = 1;
75 const int SignalFilter::FILTER_METHOD_FOURIER_TABLE = 2;
76 const int SignalFilter::FILTER_METHOD_FFT = 3;
78 const int SignalFilter::FILTER_METHOD_FFTW = 4;
79 const int SignalFilter::FILTER_METHOD_RFFTW =5 ;
82 const char* SignalFilter::s_aszFilterMethodName[] = {
93 const char* SignalFilter::s_aszFilterMethodTitle[] = {
96 {"Fouier Trigometric Table Lookout"},
100 {"Real/Half-Complex FFTW"},
104 const int SignalFilter::s_iFilterMethodCount = sizeof(s_aszFilterMethodName) / sizeof(const char*);
107 const int SignalFilter::DOMAIN_INVALID = -1;
108 const int SignalFilter::DOMAIN_FREQUENCY = 0;
109 const int SignalFilter::DOMAIN_SPATIAL = 1;
111 const char* SignalFilter::s_aszDomainName[] = {
116 const char* SignalFilter::s_aszDomainTitle[] = {
121 const int SignalFilter::s_iDomainCount = sizeof(s_aszDomainName) / sizeof(const char*);
125 * SignalFilter::SignalFilter Construct a signal
128 * f = SignalFilter (filt_type, bw, filterMin, filterMax, n, param, domain, analytic)
129 * double f Generated filter vector
130 * int filt_type Type of filter wanted
131 * double bw Bandwidth of filter
132 * double filterMin, filterMax Filter limits
133 * int nSignalPoints Number of points in signal
134 * double param General input parameter to filters
135 * int domain FREQUENCY or SPATIAL domain wanted
138 SignalFilter::SignalFilter (const char* filterName, const char* filterMethodName, double bw, double signalIncrement, int nSignalPoints, double param, const char* domainName, int zeropad = 0, int preinterpolationFactor = 1)
139 : m_vecFilter(NULL), m_vecFourierCosTable(NULL), m_vecFourierSinTable(NULL), m_fail(false)
141 m_idFilter = convertFilterNameToID (filterName);
142 if (m_idFilter == FILTER_INVALID) {
144 m_failMessage = "Invalid Filter name ";
145 m_failMessage += filterName;
148 m_idFilterMethod = convertFilterMethodNameToID (filterMethodName);
149 if (m_idFilterMethod == FILTER_METHOD_INVALID) {
151 m_failMessage = "Invalid filter method name ";
152 m_failMessage += filterMethodName;
155 m_idDomain = convertDomainNameToID (domainName);
156 if (m_idDomain == DOMAIN_INVALID) {
158 m_failMessage = "Invalid domain name ";
159 m_failMessage += domainName;
162 init (m_idFilter, m_idFilterMethod, bw, signalIncrement, nSignalPoints, param, m_idDomain, zeropad, preinterpolationFactor);
165 SignalFilter::SignalFilter (const int filterID, const int filterMethodID, double bw, double signalIncrement, int nSignalPoints, double param, const int domainID, int zeropad = 0, int preinterpolationFactor = 1)
166 : m_vecFilter(NULL), m_vecFourierCosTable(NULL), m_vecFourierSinTable(NULL), m_fail(false)
168 init (filterID, filterMethodID, bw, signalIncrement, nSignalPoints, param, domainID, zeropad, preinterpolationFactor);
171 SignalFilter::SignalFilter (const char* filterName, const char* domainName, double bw, double param)
172 : m_vecFilter(NULL), m_vecFourierCosTable(NULL), m_vecFourierSinTable(NULL), m_fail(false)
177 m_filterParam = param;
178 m_idFilter = convertFilterNameToID (filterName);
179 if (m_idFilter == FILTER_INVALID) {
181 m_failMessage = "Invalid Filter name ";
182 m_failMessage += filterName;
185 m_idDomain = convertDomainNameToID (domainName);
186 if (m_idDomain == DOMAIN_INVALID) {
188 m_failMessage = "Invalid domain name ";
189 m_failMessage += domainName;
195 SignalFilter::init (const int filterID, const int filterMethodID, double bw, double signalIncrement, int nSignalPoints, double filterParam, const int domainID, int zeropad, int preinterpolationFactor)
198 m_idFilter = filterID;
199 m_idDomain = domainID;
200 m_idFilterMethod = filterMethodID;
201 if (m_idFilter == FILTER_INVALID || m_idDomain == DOMAIN_INVALID || m_idFilterMethod == FILTER_METHOD_INVALID) {
205 m_traceLevel = TRACE_NONE;
206 m_nameFilter = convertFilterIDToName (m_idFilter);
207 m_nameDomain = convertDomainIDToName (m_idDomain);
208 m_nameFilterMethod = convertFilterMethodIDToName (m_idFilterMethod);
209 m_nSignalPoints = nSignalPoints;
210 m_signalInc = signalIncrement;
211 m_filterParam = filterParam;
213 m_preinterpolationFactor = preinterpolationFactor;
215 m_vecFourierCosTable = NULL;
216 m_vecFourierSinTable = NULL;
219 if (m_idFilterMethod == FILTER_METHOD_FFT) {
221 m_idFilterMethod = FILTER_METHOD_RFFTW;
224 m_failMessage = "FFT not yet implemented";
229 if (m_idFilterMethod == FILTER_METHOD_FOURIER || m_idFilterMethod == FILTER_METHOD_FOURIER_TABLE || m_idFilterMethod == FILTER_METHOD_FFT
231 || m_idFilterMethod == FILTER_METHOD_FFTW || m_idFilterMethod == FILTER_METHOD_RFFTW
234 m_nFilterPoints = m_nSignalPoints;
236 double logBase2 = log(m_nSignalPoints) / log(2);
237 int nextPowerOf2 = static_cast<int>(floor(logBase2));
238 if (logBase2 != floor(logBase2))
240 nextPowerOf2 += (m_zeropad - 1);
241 m_nFilterPoints = 1 << nextPowerOf2;
242 if (m_traceLevel >= TRACE_TEXT)
243 cout << "nFilterPoints = " << m_nFilterPoints << endl;
245 m_nOutputPoints = m_nFilterPoints * m_preinterpolationFactor;
246 m_filterMin = -1. / (2 * m_signalInc);
247 m_filterMax = 1. / (2 * m_signalInc);
248 m_filterInc = (m_filterMax - m_filterMin) / m_nFilterPoints;
249 m_vecFilter = new double [m_nFilterPoints];
250 int halfFilter = m_nFilterPoints / 2;
251 for (int i = 0; i <= halfFilter; i++)
252 m_vecFilter[i] = static_cast<double>(i) / halfFilter/ (2. * m_signalInc);
253 for (int i = 1; i <= halfFilter; i++)
254 m_vecFilter[m_nFilterPoints - i] = static_cast<double>(i) / halfFilter / (2. * m_signalInc);
257 // precalculate sin and cosine tables for fourier transform
258 if (m_idFilterMethod == FILTER_METHOD_FOURIER_TABLE) {
259 int nFourier = max(m_nFilterPoints,m_nOutputPoints) * max(m_nFilterPoints, m_nOutputPoints) + 1;
260 double angleIncrement = (2. * PI) / m_nFilterPoints;
261 m_vecFourierCosTable = new double[ nFourier ];
262 m_vecFourierSinTable = new double[ nFourier ];
264 for (int i = 0; i < nFourier; i++) {
265 m_vecFourierCosTable[i] = cos (angle);
266 m_vecFourierSinTable[i] = sin (angle);
267 angle += angleIncrement;
272 if (m_idFilterMethod == FILTER_METHOD_FFTW || m_idFilterMethod == FILTER_METHOD_RFFTW) {
273 for (int i = 0; i < m_nFilterPoints; i++) //fftw uses unnormalized fft
274 m_vecFilter[i] /= m_nFilterPoints;
277 if (m_idFilterMethod == FILTER_METHOD_RFFTW) {
278 m_realPlanForward = rfftw_create_plan (m_nFilterPoints, FFTW_REAL_TO_COMPLEX, FFTW_ESTIMATE);
279 m_realPlanBackward = rfftw_create_plan (m_nOutputPoints, FFTW_COMPLEX_TO_REAL, FFTW_ESTIMATE);
280 m_vecRealFftInput = new fftw_real [ m_nFilterPoints ];
281 m_vecRealFftSignal = new fftw_real [ m_nOutputPoints ];
282 for (int i = 0; i < m_nFilterPoints; i++)
283 m_vecRealFftInput[i] = 0;
284 } else if (m_idFilterMethod == FILTER_METHOD_FFTW) {
285 m_complexPlanForward = fftw_create_plan (m_nFilterPoints, FFTW_FORWARD, FFTW_ESTIMATE);
286 m_complexPlanBackward = fftw_create_plan (m_nOutputPoints, FFTW_BACKWARD, FFTW_ESTIMATE);
287 m_vecComplexFftInput = new fftw_complex [ m_nFilterPoints ];
288 m_vecComplexFftSignal = new fftw_complex [ m_nOutputPoints ];
289 for (int i = 0; i < m_nFilterPoints; i++)
290 m_vecComplexFftInput[i].re = m_vecComplexFftInput[i].im = 0;
291 for (int i = 0; i < m_nOutputPoints; i++)
292 m_vecComplexFftSignal[i].re = m_vecComplexFftSignal[i].im = 0;
296 if (m_idFilterMethod == FILTER_METHOD_CONVOLUTION) {
297 m_nFilterPoints = 2 * m_nSignalPoints - 1;
298 m_filterMin = -m_signalInc * (m_nSignalPoints - 1);
299 m_filterMax = m_signalInc * (m_nSignalPoints - 1);
300 m_filterInc = (m_filterMax - m_filterMin) / (m_nFilterPoints - 1);
301 m_vecFilter = new double[ m_nFilterPoints ];
303 if (m_idFilter == FILTER_SHEPP) {
305 double c = - 4. / (a * a);
306 int center = (m_nFilterPoints - 1) / 2;
307 int sidelen = center;
308 m_vecFilter[center] = 4. / (a * a);
310 for (int i = 1; i <= sidelen; i++ )
311 m_vecFilter [center + i] = m_vecFilter [center - i] = c / (4 * (i * i) - 1);
312 } else if (m_idDomain == DOMAIN_FREQUENCY) {
315 for (x = m_filterMin, i = 0; i < m_nFilterPoints; x += m_filterInc, i++)
316 m_vecFilter[i] = frequencyResponse (x, m_filterParam);
317 } else if (m_idDomain == DOMAIN_SPATIAL) {
320 for (x = m_filterMin, i = 0; i < m_nFilterPoints; x += m_filterInc, i++) {
321 if (haveAnalyticSpatial(m_idFilter))
322 m_vecFilter[i] = spatialResponseAnalytic (x, m_filterParam);
324 m_vecFilter[i] = spatialResponseCalc (x, m_filterParam);
325 #if LIMIT_BANDWIDTH_TRIAL
326 if (i < m_nFilterPoints / 4 || i > (m_nFilterPoints * 3) / 4)
331 m_failMessage = "Illegal domain name ";
332 m_failMessage += m_idDomain;
338 SignalFilter::~SignalFilter (void)
340 delete [] m_vecFilter;
341 delete [] m_vecFourierSinTable;
342 delete [] m_vecFourierCosTable;
345 if (m_idFilterMethod == FILTER_METHOD_FFTW) {
346 fftw_destroy_plan(m_complexPlanForward);
347 fftw_destroy_plan(m_complexPlanBackward);
348 delete [] m_vecComplexFftInput;
349 delete [] m_vecComplexFftSignal;
351 if (m_idFilterMethod == FILTER_METHOD_RFFTW) {
352 rfftw_destroy_plan(m_realPlanForward);
353 rfftw_destroy_plan(m_realPlanBackward);
354 delete [] m_vecRealFftInput;
355 delete [] m_vecRealFftSignal;
362 SignalFilter::convertFilterNameToID (const char *filterName)
364 int filterID = FILTER_INVALID;
366 for (int i = 0; i < s_iFilterCount; i++)
367 if (strcasecmp (filterName, s_aszFilterName[i]) == 0) {
376 SignalFilter::convertFilterIDToName (const int filterID)
378 static const char *name = "";
380 if (filterID >= 0 && filterID < s_iFilterCount)
381 return (s_aszFilterName [filterID]);
387 SignalFilter::convertFilterIDToTitle (const int filterID)
389 static const char *title = "";
391 if (filterID >= 0 && filterID < s_iFilterCount)
392 return (s_aszFilterTitle [filterID]);
398 SignalFilter::convertFilterMethodNameToID (const char* const filterMethodName)
400 int fmID = FILTER_METHOD_INVALID;
402 for (int i = 0; i < s_iFilterMethodCount; i++)
403 if (strcasecmp (filterMethodName, s_aszFilterMethodName[i]) == 0) {
412 SignalFilter::convertFilterMethodIDToName (const int fmID)
414 static const char *name = "";
416 if (fmID >= 0 && fmID < s_iFilterMethodCount)
417 return (s_aszFilterMethodName [fmID]);
423 SignalFilter::convertFilterMethodIDToTitle (const int fmID)
425 static const char *title = "";
427 if (fmID >= 0 && fmID < s_iFilterMethodCount)
428 return (s_aszFilterTitle [fmID]);
434 SignalFilter::convertDomainNameToID (const char* const domainName)
436 int dID = DOMAIN_INVALID;
438 for (int i = 0; i < s_iDomainCount; i++)
439 if (strcasecmp (domainName, s_aszDomainName[i]) == 0) {
448 SignalFilter::convertDomainIDToName (const int domainID)
450 static const char *name = "";
452 if (domainID >= 0 && domainID < s_iDomainCount)
453 return (s_aszDomainName [domainID]);
459 SignalFilter::convertDomainIDToTitle (const int domainID)
461 static const char *title = "";
463 if (domainID >= 0 && domainID < s_iDomainCount)
464 return (s_aszDomainTitle [domainID]);
470 SignalFilter::filterSignal (const float input[], double output[]) const
472 if (m_idFilterMethod == FILTER_METHOD_CONVOLUTION) {
473 for (int i = 0; i < m_nSignalPoints; i++)
474 output[i] = convolve (input, m_signalInc, i, m_nSignalPoints);
475 } else if (m_idFilterMethod == FILTER_METHOD_FOURIER) {
476 double inputSignal[m_nFilterPoints];
477 for (int i = 0; i < m_nSignalPoints; i++)
478 inputSignal[i] = input[i];
479 for (int i = m_nSignalPoints; i < m_nFilterPoints; i++)
480 inputSignal[i] = 0; // zeropad
481 complex<double> fftSignal[m_nFilterPoints];
482 finiteFourierTransform (inputSignal, fftSignal, m_nFilterPoints, -1);
483 for (int i = 0; i < m_nFilterPoints; i++)
484 fftSignal[i] *= m_vecFilter[i];
485 double inverseFourier[m_nFilterPoints];
486 finiteFourierTransform (fftSignal, inverseFourier, m_nFilterPoints, 1);
487 for (int i = 0; i < m_nSignalPoints; i++)
488 output[i] = inverseFourier[i];
489 } else if (m_idFilterMethod == FILTER_METHOD_FOURIER_TABLE) {
490 double inputSignal[m_nFilterPoints];
491 for (int i = 0; i < m_nSignalPoints; i++)
492 inputSignal[i] = input[i];
493 for (int i = m_nSignalPoints; i < m_nFilterPoints; i++)
494 inputSignal[i] = 0; // zeropad
495 complex<double> fftSignal[m_nFilterPoints];
496 finiteFourierTransform (inputSignal, fftSignal, -1);
497 for (int i = 0; i < m_nFilterPoints; i++)
498 fftSignal[i] *= m_vecFilter[i];
499 double inverseFourier[m_nFilterPoints];
500 finiteFourierTransform (fftSignal, inverseFourier, 1);
501 for (int i = 0; i < m_nSignalPoints; i++)
502 output[i] = inverseFourier[i];
505 else if (m_idFilterMethod == FILTER_METHOD_RFFTW) {
506 for (int i = 0; i < m_nSignalPoints; i++)
507 m_vecRealFftInput[i] = input[i];
509 fftw_real fftOutput [ m_nFilterPoints ];
510 rfftw_one (m_realPlanForward, m_vecRealFftInput, fftOutput);
511 for (int i = 0; i < m_nFilterPoints; i++)
512 m_vecRealFftSignal[i] = m_vecFilter[i] * fftOutput[i];
513 for (int i = m_nFilterPoints; i < m_nOutputPoints; i++)
514 m_vecRealFftSignal[i] = 0;
516 fftw_real ifftOutput [ m_nOutputPoints ];
517 rfftw_one(m_realPlanBackward, m_vecRealFftSignal, ifftOutput);
518 for (int i = 0; i < m_nSignalPoints * m_preinterpolationFactor; i++)
519 output[i] = ifftOutput[i];
520 } else if (m_idFilterMethod == FILTER_METHOD_FFTW) {
521 for (int i = 0; i < m_nSignalPoints; i++)
522 m_vecComplexFftInput[i].re = input[i];
524 fftw_complex fftOutput [ m_nFilterPoints ];
525 fftw_one(m_complexPlanForward, m_vecComplexFftInput, fftOutput);
526 for (int i = 0; i < m_nFilterPoints; i++) {
527 m_vecComplexFftSignal[i].re = m_vecFilter[i] * fftOutput[i].re;
528 m_vecComplexFftSignal[i].im = m_vecFilter[i] * fftOutput[i].im;
530 fftw_complex ifftOutput [ m_nOutputPoints ];
531 fftw_one(m_complexPlanBackward, m_vecComplexFftSignal, ifftOutput);
532 for (int i = 0; i < m_nSignalPoints * m_preinterpolationFactor; i++)
533 output[i] = ifftOutput[i].re;
539 SignalFilter::response (double x)
543 if (m_idDomain == DOMAIN_SPATIAL)
544 response = spatialResponse (m_idFilter, m_bw, x, m_filterParam);
545 else if (m_idDomain == DOMAIN_FREQUENCY)
546 response = frequencyResponse (m_idFilter, m_bw, x, m_filterParam);
553 SignalFilter::spatialResponse (int filterID, double bw, double x, double param)
555 if (haveAnalyticSpatial(filterID))
556 return spatialResponseAnalytic (filterID, bw, x, param);
558 return spatialResponseCalc (filterID, bw, x, param, N_INTEGRAL);
562 * filter_spatial_response_calc Calculate filter by discrete inverse fourier
563 * transform of filters's frequency
567 * y = filter_spatial_response_calc (filt_type, x, m_bw, param, n)
568 * double y Filter's response in spatial domain
569 * int filt_type Type of filter (definitions in ct.h)
570 * double x Spatial position to evaluate filter
571 * double m_bw Bandwidth of window
572 * double param General parameter for various filters
573 * int n Number of points to calculate integrations
577 SignalFilter::spatialResponseCalc (double x, double param) const
579 return (spatialResponseCalc (m_idFilter, m_bw, x, param, N_INTEGRAL));
583 SignalFilter::spatialResponseCalc (int filterID, double bw, double x, double param, int n)
587 if (filterID == FILTER_TRIANGLE) {
594 double zinc = (zmax - zmin) / (n - 1);
598 for (int i = 0; i < n; i++, z += zinc)
599 q[i] = frequencyResponse (filterID, bw, z, param) * cos (TWOPI * z * x);
601 double y = 2 * integrateSimpson (zmin, zmax, q, n);
608 * filter_frequency_response Return filter frequency response
611 * h = filter_frequency_response (filt_type, u, m_bw, param)
612 * double h Filters frequency response at u
613 * int filt_type Type of filter
614 * double u Frequency to evaluate filter at
615 * double m_bw Bandwidth of filter
616 * double param General input parameter for various filters
620 SignalFilter::frequencyResponse (double u, double param) const
622 return frequencyResponse (m_idFilter, m_bw, u, param);
627 SignalFilter::frequencyResponse (int filterID, double bw, double u, double param)
630 double au = fabs (u);
633 case FILTER_BANDLIMIT:
639 case FILTER_ABS_BANDLIMIT:
645 case FILTER_TRIANGLE:
655 q = cos(PI * u / bw);
657 case FILTER_ABS_COSINE:
661 q = au * cos(PI * u / bw);
664 q = bw * sinc (PI * bw * u, 1.);
666 case FILTER_ABS_SINC:
667 q = au * bw * sinc (PI * bw * u, 1.);
669 case FILTER_G_HAMMING:
673 q = param + (1 - param) * cos (TWOPI * u / bw);
675 case FILTER_ABS_G_HAMMING:
679 q = au * (param + (1 - param) * cos(TWOPI * u / bw));
683 sys_error (ERR_WARNING, "Frequency response for filter %d not implemented [filter_frequency_response]", filterID);
692 * filter_spatial_response_analytic Calculate filter by analytic inverse fourier
693 * transform of filters's frequency
697 * y = filter_spatial_response_analytic (filt_type, x, m_bw, param)
698 * double y Filter's response in spatial domain
699 * int filt_type Type of filter (definitions in ct.h)
700 * double x Spatial position to evaluate filter
701 * double m_bw Bandwidth of window
702 * double param General parameter for various filters
706 SignalFilter::spatialResponseAnalytic (double x, double param) const
708 return spatialResponseAnalytic (m_idFilter, m_bw, x, param);
712 SignalFilter::haveAnalyticSpatial (int filterID)
714 bool haveAnalytic = false;
717 case FILTER_BANDLIMIT:
718 case FILTER_TRIANGLE:
720 case FILTER_G_HAMMING:
721 case FILTER_ABS_BANDLIMIT:
722 case FILTER_ABS_COSINE:
723 case FILTER_ABS_G_HAMMING:
732 return (haveAnalytic);
736 SignalFilter::spatialResponseAnalytic (int filterID, double bw, double x, double param)
739 double u = TWOPI * x;
742 double b2 = TWOPI / bw;
745 case FILTER_BANDLIMIT:
746 q = bw * sinc(u * w, 1.0);
748 case FILTER_TRIANGLE:
749 temp = sinc (u * w, 1.0);
750 q = bw * temp * temp;
753 q = sinc(b-u,w) + sinc(b+u,w);
755 case FILTER_G_HAMMING:
756 q = 2 * param * sin(u*w)/u + (1-param) * (sinc(b2-u, w) + sinc(b2+u, w));
758 case FILTER_ABS_BANDLIMIT:
759 q = 2 * integral_abscos (u, w);
761 case FILTER_ABS_COSINE:
762 q = integral_abscos(b-u,w) + integral_abscos(b+u,w);
764 case FILTER_ABS_G_HAMMING:
765 q = 2 * param * integral_abscos(u,w) +
766 (1-param)*(integral_abscos(u-b2,w)+integral_abscos(u+b2,w));
770 q = 4. / (PI * bw * bw);
772 q = fabs ((2 / bw) * sin (u * w)) * sinc (u * w, 1.) * sinc (u * w, 1.);
775 if (fabs (x) < bw / 2)
780 case FILTER_ABS_SINC:
782 sys_error (ERR_WARNING, "Analytic filter type %d not implemented [filter_spatial_response_analytic]", filterID);
792 * sinc Return sin(x)/x function
796 * double v sinc value
800 * v = sin(x * mult) / x;
805 * integral_abscos Returns integral of u*cos(u)
808 * q = integral_abscos (u, w)
809 * double q Integral value
810 * double u Integration variable
811 * double w Upper integration boundary
814 * Returns the value of integral of u*cos(u)*dV for V = 0 to w
818 SignalFilter::integral_abscos (double u, double w)
820 return (fabs (u) > F_EPSILON
821 ? (cos(u * w) - 1) / (u * u) + w / u * sin (u * w)
827 * convolve Discrete convolution of two functions
830 * r = convolve (f1, f2, dx, n, np, func_type)
831 * double r Convolved result
832 * double f1[], f2[] Functions to be convolved
833 * double dx Difference between successive x values
834 * int n Array index to center convolution about
835 * int np Number of points in f1 array
836 * int func_type EVEN or ODD or EVEN_AND_ODD function f2
839 * f1 is the projection data, its indices range from 0 to np - 1.
840 * The index for f2, the filter, ranges from -(np-1) to (np-1).
841 * There are 3 ways to handle the negative vertices of f2:
842 * 1. If we know f2 is an EVEN function, then f2[-n] = f2[n].
843 * All filters used in reconstruction are even.
844 * 2. If we know f2 is an ODD function, then f2[-n] = -f2[n]
845 * 3. If f2 is both ODD AND EVEN, then we must store the value of f2
846 * for negative indices. Since f2 must range from -(np-1) to (np-1),
847 * if we add (np - 1) to f2's array index, then f2's index will
848 * range from 0 to 2 * (np - 1), and the origin, x = 0, will be
849 * stored at f2[np-1].
853 SignalFilter::convolve (const double func[], const double dx, const int n, const int np) const
857 #if UNOPTIMIZED_CONVOLUTION
858 for (int i = 0; i < np; i++)
859 sum += func[i] * m_vecFilter[n - i + (np - 1)];
861 double* f2 = m_vecFilter + n + (np - 1);
862 for (int i = 0; i < np; i++)
863 sum += *func++ * *f2--;
871 SignalFilter::convolve (const float func[], const double dx, const int n, const int np) const
875 #if UNOPTIMIZED_CONVOLUTION
876 for (int i = 0; i < np; i++)
877 sum += func[i] * m_vecFilter[n - i + (np - 1)];
879 double* f2 = m_vecFilter + n + (np - 1);
880 for (int i = 0; i < np; i++)
881 sum += *func++ * *f2--;
889 SignalFilter::finiteFourierTransform (const double input[], complex<double> output[], const int n, int direction)
896 double angleIncrement = direction * 2 * PI / n;
897 for (int i = 0; i < n; i++) {
900 for (int j = 0; j < n; j++) {
901 double angle = i * j * angleIncrement;
902 sumReal += input[j] * cos(angle);
903 sumImag += input[j] * sin(angle);
909 output[i] = complex<double> (sumReal, sumImag);
915 SignalFilter::finiteFourierTransform (const complex<double> input[], complex<double> output[], const int n, int direction)
922 double angleIncrement = direction * 2 * PI / n;
923 for (int i = 0; i < n; i++) {
924 complex<double> sum (0,0);
925 for (int j = 0; j < n; j++) {
926 double angle = i * j * angleIncrement;
927 complex<double> exponentTerm (cos(angle), sin(angle));
928 sum += input[j] * exponentTerm;
938 SignalFilter::finiteFourierTransform (const complex<double> input[], double output[], const int n, int direction)
945 double angleIncrement = direction * 2 * PI / n;
946 for (int i = 0; i < n; i++) {
948 for (int j = 0; j < n; j++) {
949 double angle = i * j * angleIncrement;
950 sumReal += input[j].real() * cos(angle) - input[j].imag() * sin(angle);
960 SignalFilter::finiteFourierTransform (const double input[], complex<double> output[], int direction) const
967 for (int i = 0; i < m_nFilterPoints; i++) {
968 double sumReal = 0, sumImag = 0;
969 for (int j = 0; j < m_nFilterPoints; j++) {
970 int tableIndex = i * j;
972 sumReal += input[j] * m_vecFourierCosTable[tableIndex];
973 sumImag += input[j] * m_vecFourierSinTable[tableIndex];
975 sumReal += input[j] * m_vecFourierCosTable[tableIndex];
976 sumImag -= input[j] * m_vecFourierSinTable[tableIndex];
980 sumReal /= m_nFilterPoints;
981 sumImag /= m_nFilterPoints;
983 output[i] = complex<double> (sumReal, sumImag);
987 // (a+bi) * (c + di) = (ac - bd) + (ad + bc)i
989 SignalFilter::finiteFourierTransform (const complex<double> input[], complex<double> output[], int direction) const
996 for (int i = 0; i < m_nFilterPoints; i++) {
997 double sumReal = 0, sumImag = 0;
998 for (int j = 0; j < m_nFilterPoints; j++) {
999 int tableIndex = i * j;
1000 if (direction > 0) {
1001 sumReal += input[j].real() * m_vecFourierCosTable[tableIndex]
1002 - input[j].imag() * m_vecFourierSinTable[tableIndex];
1003 sumImag += input[j].real() * m_vecFourierSinTable[tableIndex]
1004 + input[j].imag() * m_vecFourierCosTable[tableIndex];
1006 sumReal += input[j].real() * m_vecFourierCosTable[tableIndex]
1007 - input[j].imag() * -m_vecFourierSinTable[tableIndex];
1008 sumImag += input[j].real() * -m_vecFourierSinTable[tableIndex]
1009 + input[j].imag() * m_vecFourierCosTable[tableIndex];
1012 if (direction < 0) {
1013 sumReal /= m_nFilterPoints;
1014 sumImag /= m_nFilterPoints;
1016 output[i] = complex<double> (sumReal, sumImag);
1021 SignalFilter::finiteFourierTransform (const complex<double> input[], double output[], int direction) const
1028 for (int i = 0; i < m_nFilterPoints; i++) {
1030 for (int j = 0; j < m_nFilterPoints; j++) {
1031 int tableIndex = i * j;
1032 if (direction > 0) {
1033 sumReal += input[j].real() * m_vecFourierCosTable[tableIndex]
1034 - input[j].imag() * m_vecFourierSinTable[tableIndex];
1036 sumReal += input[j].real() * m_vecFourierCosTable[tableIndex]
1037 - input[j].imag() * -m_vecFourierSinTable[tableIndex];
1040 if (direction < 0) {
1041 sumReal /= m_nFilterPoints;
1043 output[i] = sumReal;