logcurve.h

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/*
    Copyright (C) 2001 Steve Harris & Paul Davis

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/

#ifndef __ardour_logcurve_h__
#define __ardour_logcurve_h__

#include "pbd/fastlog.h"
#include <glibmm/threads.h>

namespace ARDOUR {

class LIBARDOUR_API LogCurve {
  public:
        LogCurve (float steepness = 0.2, uint32_t len = 0) {
                l = len;
                S = steepness;
                a = log(S);
                b = 1.0f / log(1.0f + (1.0f / S));
        }

        bool operator== (const LogCurve& other) const {
                return S == other.S && l == other.l;
        }

        bool operator!= (const LogCurve& other) const {
                return S != other.S || l != other.l;
        }

        float value (float frac) const {
                return (fast_log(frac + S) - a) * b;
        }

        float value (uint32_t pos) const {
                return (fast_log(((float) pos/l) + S) - a) * b;
        }

        float invert_value (float frac) const {
                return (a - fast_log(frac + S)) * b;
        }

        float invert_value (uint32_t pos) const {
                return (a - fast_log(((float) pos/l) + S)) * b;
        }

        void fill (float *vec, uint32_t veclen, bool invert) const {
                float dx = 1.0f/veclen;
                float x;
                uint32_t i;

                if (!invert) {

                        vec[0] = 0.0;
                        vec[veclen-1] = 1.0;

                        for (i = 1, x = 0; i < veclen - 1; x += dx, i++) {
                                vec[i] = value (x);
                        }

                } else {

                        vec[0] = 1.0;
                        vec[veclen-1] = 0.0;

                        for (i = veclen-2, x = 0.0f; i > 0; x += dx, i--) {
                                vec[i] = value (x);
                        }
                }
        }

        float steepness() const { return S; }
        uint32_t length() const { return l; }

        void set_steepness (float steepness) {
                S = steepness;
                a = log(S);
                b = 1.0f / log(1.0f + (1.0f / S));
        }
        void set_length (uint32_t len) { l = len; }

        mutable Glib::Threads::Mutex lock;

  protected:
        float a;
        float b;
        float S;
        uint32_t l;
};

class LIBARDOUR_API LogCurveIn : public LogCurve
{
  public:
        LogCurveIn (float steepness = 0.2, uint32_t len = 0)
                : LogCurve (steepness, len) {}

        float value (float frac) const {
                return (fast_log(frac + S) - a) * b;
        }

        float value (uint32_t pos) const {
                return (fast_log(((float) pos/l) + S) - a) * b;
        }
};

class LIBARDOUR_API LogCurveOut : public LogCurve
{
  public:
        LogCurveOut (float steepness = 0.2, uint32_t len = 0)
                : LogCurve (steepness, len) {}

};

} // namespace ARDOUR

#endif /* __ardour_logcurve_h__ */