tomwalters@116: /*!
tomwalters@116:  * \file
tomwalters@116:  * \brief Logarithmic frequency scale for generating filter banks and their frequencies
tomwalters@116:  *
tomwalters@116:  * \author Willem van Engen <cnbh@willem.engen.nl>
tomwalters@116:  * \date created 2006/09/28
tomwalters@116:  * \version \$Id: ScaleLog.h 459 2007-11-08 11:50:04Z tom $
tomwalters@116:  */
tomwalters@116: /* (c) 2006, University of Cambridge, Medical Research Council
tomwalters@116:  * http://www.pdn.cam.ac.uk/groups/cnbh/aimmanual
tomwalters@116:  */
tomwalters@116: #ifndef __MODULE_SCALE_LOG_H__
tomwalters@116: #define __MODULE_SCALE_LOG_H__
tomwalters@116: 
tomwalters@116: #include <math.h>
tomwalters@116: 
tom@230: #include "Modules/Output/Graphics/Scale/Scale.h"
tom@230: 
tom@230: namespace aimc {
tomwalters@116: 
tomwalters@116: /*!
tomwalters@116:  * \class ScaleLog "Modules/Scale/ScaleLog.h"
tomwalters@116:  * \brief Logarithmic frequency scale for generating filter banks and their frequencies
tomwalters@116:  *
tomwalters@116:  * It is very advisable to use Scale::Create() to an instance of this scale.
tomwalters@116:  */
tomwalters@116: class ScaleLog : public Scale {
tomwalters@116: public:
tomwalters@228:   ScaleLog(unsigned int min, unsigned int max, float density)
tomwalters@228:     : Scale(min, max, density) { m_iType = SCALE_LOG; m_sName="log"; };
tomwalters@116: 
tomwalters@228:   /*! The log scale has a problem, because log(0)=inf, so all values below
tomwalters@228:    *  1e-5 are truncated to 1e-5. */
tomwalters@228:   float FromLinear(float fFreq) {
tomwalters@228:     if (fFreq<1e-5f) fFreq=1e-5f;
tomwalters@228:     return log(fFreq);
tomwalters@228:   };
tomwalters@116: 
tomwalters@228:   float ToLinear(float fFreq) {
tomwalters@228:     return exp(fFreq);
tomwalters@228:   };
tomwalters@116: };
tom@230: }  // namespace aimc
tomwalters@116: #endif /* __MODULE_SCALE_LOG_H__ */