2 /*****************************************************************************
6 ** Purpose: Routines for signal-procesing filters
7 ** Progammer: Kevin Rosenberg
8 ** Date Started: Aug 1984
10 ** This is part of the CTSim program
11 ** Copyright (C) 1983-2000 Kevin Rosenberg
13 ** $Id: filter.cpp,v 1.30 2000/11/28 14:54:07 kevin Exp $
15 ** This program is free software; you can redistribute it and/or modify
16 ** it under the terms of the GNU General Public License (version 2) as
17 ** published by the Free Software Foundation.
19 ** This program is distributed in the hope that it will be useful,
20 ** but WITHOUT ANY WARRANTY; without even the implied warranty of
21 ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 ** GNU General Public License for more details.
24 ** You should have received a copy of the GNU General Public License
25 ** along with this program; if not, write to the Free Software
26 ** Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
27 ******************************************************************************/
31 int SignalFilter::N_INTEGRAL=500; //static member
33 const int SignalFilter::FILTER_INVALID = -1 ;
34 const int SignalFilter::FILTER_ABS_BANDLIMIT = 0; // filter times |x = |
35 const int SignalFilter::FILTER_ABS_G_HAMMING = 1;
36 const int SignalFilter::FILTER_ABS_COSINE = 2;
37 const int SignalFilter::FILTER_ABS_SINC = 3;
38 const int SignalFilter::FILTER_SHEPP = 4;
39 const int SignalFilter::FILTER_BANDLIMIT = 5;
40 const int SignalFilter::FILTER_SINC = 6;
41 const int SignalFilter::FILTER_G_HAMMING = 7;
42 const int SignalFilter::FILTER_COSINE = 8;
43 const int SignalFilter::FILTER_TRIANGLE = 9;
45 const char* SignalFilter::s_aszFilterName[] = {
58 const char* SignalFilter::s_aszFilterTitle[] = {
59 {"Abs(w) * Bandlimit"},
71 const int SignalFilter::s_iFilterCount = sizeof(s_aszFilterName) / sizeof(const char*);
74 const int SignalFilter::DOMAIN_INVALID = -1;
75 const int SignalFilter::DOMAIN_FREQUENCY = 0;
76 const int SignalFilter::DOMAIN_SPATIAL = 1;
78 const char* SignalFilter::s_aszDomainName[] = {
83 const char* SignalFilter::s_aszDomainTitle[] = {
88 const int SignalFilter::s_iDomainCount = sizeof(s_aszDomainName) / sizeof(const char*);
92 * SignalFilter::SignalFilter Construct a signal
95 * f = SignalFilter (filt_type, bw, filterMin, filterMax, n, param, domain, analytic)
96 * double f Generated filter vector
97 * int filt_type Type of filter wanted
98 * double bw Bandwidth of filter
99 * double filterMin, filterMax Filter limits
100 * int nFilterPoints Number of points in signal
101 * double param General input parameter to filters
102 * int domain FREQUENCY or SPATIAL domain wanted
105 SignalFilter::SignalFilter (const char* szFilterName, double dFilterMinimum, double dFilterMaximum, int nFilterPoints, double dBandwidth, double dFilterParam, const char* szDomainName)
106 : m_adFilter(NULL), m_fail(false)
108 m_idFilter = convertFilterNameToID (szFilterName);
109 if (m_idFilter == FILTER_INVALID) {
111 m_failMessage = "Invalid Filter name ";
112 m_failMessage += szFilterName;
115 m_idDomain = convertDomainNameToID (szDomainName);
116 if (m_idDomain == DOMAIN_INVALID) {
118 m_failMessage = "Invalid domain name ";
119 m_failMessage += szDomainName;
122 init (m_idFilter, dFilterMinimum, dFilterMaximum, nFilterPoints, dBandwidth, dFilterParam, m_idDomain);
125 SignalFilter::SignalFilter (const int idFilter, double dFilterMinimum, double dFilterMaximum, int nFilterPoints, double dBandwidth, double dFilterParam, const int idDomain)
126 : m_adFilter(NULL), m_fail(false)
128 init (idFilter, dFilterMinimum, dFilterMaximum, nFilterPoints, dBandwidth, dFilterParam, idDomain);
131 SignalFilter::SignalFilter (const char* szFilterName, const char* szDomainName, double dBandwidth, double dFilterParam)
132 : m_adFilter(NULL), m_fail(false)
135 m_dBandwidth = dBandwidth;
136 m_dFilterParam = dFilterParam;
137 m_idFilter = convertFilterNameToID (szFilterName);
138 if (m_idFilter == FILTER_INVALID) {
140 m_failMessage = "Invalid Filter name ";
141 m_failMessage += szFilterName;
144 m_idDomain = convertDomainNameToID (szDomainName);
145 if (m_idDomain == DOMAIN_INVALID) {
147 m_failMessage = "Invalid domain name ";
148 m_failMessage += szDomainName;
154 SignalFilter::init (const int idFilter, double dFilterMinimum, double dFilterMaximum, int nFilterPoints, double dBandwidth, double dFilterParam, const int idDomain)
156 m_idFilter = idFilter;
157 m_idDomain = idDomain;
158 if (m_idFilter == FILTER_INVALID || m_idDomain == DOMAIN_INVALID) {
162 if (nFilterPoints < 2) {
164 m_failMessage = "Number of filter points ";
165 m_failMessage += nFilterPoints;
166 m_failMessage = " less than 2";
170 m_nameFilter = convertFilterIDToName (m_idFilter);
171 m_nameDomain = convertDomainIDToName (m_idDomain);
172 m_nFilterPoints = nFilterPoints;
173 m_dFilterParam = dFilterParam;
174 m_dBandwidth = dBandwidth;
175 m_dFilterMin = dFilterMinimum;
176 m_dFilterMax = dFilterMaximum;
178 m_dFilterInc = (m_dFilterMax - m_dFilterMin) / (m_nFilterPoints - 1);
179 m_adFilter = new double [m_nFilterPoints];
181 if (m_idDomain == DOMAIN_FREQUENCY)
182 createFrequencyFilter (m_adFilter);
183 else if (m_idDomain == DOMAIN_SPATIAL)
184 createSpatialFilter (m_adFilter);
188 SignalFilter::~SignalFilter (void)
190 delete [] m_adFilter;
194 SignalFilter::createFrequencyFilter (double* adFilter) const
198 for (x = m_dFilterMin, i = 0; i < m_nFilterPoints; x += m_dFilterInc, i++)
199 adFilter[i] = frequencyResponse (x);
204 SignalFilter::createSpatialFilter (double* adFilter) const
206 if (m_idFilter == FILTER_SHEPP) {
207 double a = 2 * m_dBandwidth;
208 double c = - 4. / (a * a);
209 int center = (m_nFilterPoints - 1) / 2;
210 int sidelen = center;
211 m_adFilter[center] = 4. / (a * a);
213 for (int i = 1; i <= sidelen; i++ )
214 m_adFilter [center + i] = m_adFilter [center - i] = c / (4 * (i * i) - 1);
216 double x = m_dFilterMin;
217 for (int i = 0; i < m_nFilterPoints; i++, x += m_dFilterInc) {
218 if (haveAnalyticSpatial(m_idFilter))
219 m_adFilter[i] = spatialResponseAnalytic (x);
221 m_adFilter[i] = spatialResponseCalc (x);
227 SignalFilter::convertFilterNameToID (const char *filterName)
229 int filterID = FILTER_INVALID;
231 for (int i = 0; i < s_iFilterCount; i++)
232 if (strcasecmp (filterName, s_aszFilterName[i]) == 0) {
241 SignalFilter::convertFilterIDToName (const int filterID)
243 static const char *name = "";
245 if (filterID >= 0 && filterID < s_iFilterCount)
246 return (s_aszFilterName [filterID]);
252 SignalFilter::convertFilterIDToTitle (const int filterID)
254 static const char *title = "";
256 if (filterID >= 0 && filterID < s_iFilterCount)
257 return (s_aszFilterTitle [filterID]);
263 SignalFilter::convertDomainNameToID (const char* const domainName)
265 int dID = DOMAIN_INVALID;
267 for (int i = 0; i < s_iDomainCount; i++)
268 if (strcasecmp (domainName, s_aszDomainName[i]) == 0) {
277 SignalFilter::convertDomainIDToName (const int domainID)
279 static const char *name = "";
281 if (domainID >= 0 && domainID < s_iDomainCount)
282 return (s_aszDomainName [domainID]);
288 SignalFilter::convertDomainIDToTitle (const int domainID)
290 static const char *title = "";
292 if (domainID >= 0 && domainID < s_iDomainCount)
293 return (s_aszDomainTitle [domainID]);
300 SignalFilter::response (double x)
304 if (m_idDomain == DOMAIN_SPATIAL)
305 response = spatialResponse (m_idFilter, m_dBandwidth, x, m_dFilterParam);
306 else if (m_idDomain == DOMAIN_FREQUENCY)
307 response = frequencyResponse (m_idFilter, m_dBandwidth, x, m_dFilterParam);
314 SignalFilter::spatialResponse (int filterID, double bw, double x, double param)
316 if (haveAnalyticSpatial(filterID))
317 return spatialResponseAnalytic (filterID, bw, x, param);
319 return spatialResponseCalc (filterID, bw, x, param, N_INTEGRAL);
323 SignalFilter::copyFilterData (double* pdFilter, const int iStart, const int nPoints) const
325 int iFirst = clamp (iStart, 0, m_nFilterPoints - 1);
326 int iLast = clamp (iFirst + nPoints - 1, 0, m_nFilterPoints - 1);
328 for (int i = iFirst; i <= iLast; i++)
329 pdFilter[i - iFirst] = m_adFilter[i];
333 * filter_spatial_response_calc Calculate filter by discrete inverse fourier
334 * transform of filters's frequency
338 * y = filter_spatial_response_calc (filt_type, x, m_bw, param, n)
339 * double y Filter's response in spatial domain
340 * int filt_type Type of filter (definitions in ct.h)
341 * double x Spatial position to evaluate filter
342 * double m_bw Bandwidth of window
343 * double param General parameter for various filters
344 * int n Number of points to calculate integrations
348 SignalFilter::spatialResponseCalc (double x) const
350 return (spatialResponseCalc (m_idFilter, m_dBandwidth, x, m_dFilterParam, N_INTEGRAL));
354 SignalFilter::spatialResponseCalc (int filterID, double bw, double x, double param, int n)
358 if (filterID == FILTER_TRIANGLE) {
365 double zinc = (zmax - zmin) / (n - 1);
369 for (int i = 0; i < n; i++, z += zinc)
370 q[i] = frequencyResponse (filterID, bw, z, param) * cos (TWOPI * z * x);
372 double y = 2 * integrateSimpson (zmin, zmax, q, n);
379 * filter_frequency_response Return filter frequency response
382 * h = filter_frequency_response (filt_type, u, m_bw, param)
383 * double h Filters frequency response at u
384 * int filt_type Type of filter
385 * double u Frequency to evaluate filter at
386 * double m_bw Bandwidth of filter
387 * double param General input parameter for various filters
391 SignalFilter::frequencyResponse (double u) const
393 return frequencyResponse (m_idFilter, m_dBandwidth, u, m_dFilterParam);
398 SignalFilter::frequencyResponse (int filterID, double bw, double u, double param)
401 double au = fabs (u);
404 case FILTER_BANDLIMIT:
405 if (fabs(au) >= fabs(bw / 2) + F_EPSILON)
410 case FILTER_ABS_BANDLIMIT:
411 if (fabs(au) >= fabs(bw / 2) + F_EPSILON)
416 case FILTER_TRIANGLE:
417 if (fabs(au) >= fabs(bw / 2) + F_EPSILON)
423 if (fabs(au) >= fabs(bw / 2) + F_EPSILON)
426 q = cos(PI * u / bw);
428 case FILTER_ABS_COSINE:
429 if (fabs(au) >= fabs(bw / 2) + F_EPSILON)
432 q = au * cos(PI * u / bw);
435 q = bw * sinc (PI * bw * u, 1.);
437 case FILTER_ABS_SINC:
438 q = au * bw * sinc (PI * bw * u, 1.);
440 case FILTER_G_HAMMING:
441 if (fabs(au) >= fabs(bw / 2) + F_EPSILON)
444 q = param + (1 - param) * cos (TWOPI * u / bw);
446 case FILTER_ABS_G_HAMMING:
447 if (fabs(au) >= fabs(bw / 2) + F_EPSILON)
450 q = au * (param + (1 - param) * cos(TWOPI * u / bw));
454 sys_error (ERR_WARNING, "Frequency response for filter %d not implemented [filter_frequency_response]", filterID);
463 * filter_spatial_response_analytic Calculate filter by analytic inverse fourier
464 * transform of filters's frequency
468 * y = filter_spatial_response_analytic (filt_type, x, m_bw, param)
469 * double y Filter's response in spatial domain
470 * int filt_type Type of filter (definitions in ct.h)
471 * double x Spatial position to evaluate filter
472 * double m_bw Bandwidth of window
473 * double param General parameter for various filters
477 SignalFilter::spatialResponseAnalytic (double x) const
479 return spatialResponseAnalytic (m_idFilter, m_dBandwidth, x, m_dFilterParam);
483 SignalFilter::haveAnalyticSpatial (int filterID)
485 bool haveAnalytic = false;
488 case FILTER_BANDLIMIT:
489 case FILTER_TRIANGLE:
491 case FILTER_G_HAMMING:
492 case FILTER_ABS_BANDLIMIT:
493 case FILTER_ABS_COSINE:
494 case FILTER_ABS_G_HAMMING:
503 return (haveAnalytic);
507 SignalFilter::spatialResponseAnalytic (int filterID, double bw, double x, double param)
510 double u = TWOPI * x;
513 double b2 = TWOPI / bw;
516 case FILTER_BANDLIMIT:
517 q = bw * sinc(u * w, 1.0);
519 case FILTER_TRIANGLE:
520 temp = sinc (u * w, 1.0);
521 q = bw * temp * temp;
524 q = sinc(b-u,w) + sinc(b+u,w);
526 case FILTER_G_HAMMING:
527 q = 2 * param * sin(u*w)/u + (1-param) * (sinc(b2-u, w) + sinc(b2+u, w));
529 case FILTER_ABS_BANDLIMIT:
530 q = 2 * integral_abscos (u, w);
532 case FILTER_ABS_COSINE:
533 q = integral_abscos(b-u,w) + integral_abscos(b+u,w);
535 case FILTER_ABS_G_HAMMING:
536 q = 2 * param * integral_abscos(u,w) +
537 (1-param)*(integral_abscos(u-b2,w)+integral_abscos(u+b2,w));
541 q = 4. / (PI * bw * bw);
543 q = fabs ((2 / bw) * sin (u * w)) * sinc (u * w, 1.) * sinc (u * w, 1.);
546 if (fabs (x) < bw / 2)
551 case FILTER_ABS_SINC:
553 sys_error (ERR_WARNING, "Analytic filter type %d not implemented [filter_spatial_response_analytic]", filterID);
563 * sinc Return sin(x)/x function
567 * double v sinc value
571 * v = sin(x * mult) / x;
576 * integral_abscos Returns integral of u*cos(u)
579 * q = integral_abscos (u, w)
580 * double q Integral value
581 * double u Integration variable
582 * double w Upper integration boundary
585 * Returns the value of integral of u*cos(u)*dV for V = 0 to w