view layer/ColourScale.h @ 1416:d794630429a7

Fix potential divide-by-zero

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006-2016 Chris Cannam and QMUL.
    
    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.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef COLOUR_SCALE_H
#define COLOUR_SCALE_H

#include "ColourMapper.h"

enum class ColourScaleType {
    Linear,
    Meter,
    Log,
    Phase,
    PlusMinusOne,
    Absolute
};

/**
 * Map values within a range onto a set of colours, with a given
 * distribution (linear, log etc) and optional colourmap rotation.
 */
class ColourScale
{
public:
    struct Parameters {
        Parameters() : colourMap(0), scaleType(ColourScaleType::Linear),
                       minValue(0.0), maxValue(1.0), inverted(false),
                       threshold(0.0), gain(1.0), multiple(1.0) { }

        /** A colour map index as used by ColourMapper */
        int colourMap;
        
        /** Distribution for the scale */
        ColourScaleType scaleType;
        
        /** Minimum value in source range */
        double minValue;
        
        /** Maximum value in source range. Must be > minValue */
        double maxValue;

        /** Whether the colour scale should be mapped inverted */
        bool inverted;

        /** Threshold below which every value is mapped to background
            pixel 0 */
        double threshold;

        /** Gain to apply before thresholding, mapping, and clamping */
        double gain;

        /** Multiple to apply after thresholding and mapping. In most
         *  cases the gain parameter is the one you want instead of
         *  this, but this can be used for example with Log scale to
         *  produce the log of some power of the original value,
         *  e.g. multiple = 2 gives log(x^2). */
        double multiple;
    };
    
    /**
     * Create a ColourScale with the given parameters.
     *
     * Note that some parameters may be ignored for some scale
     * distribution settings. For example, min and max are ignored for
     * PlusMinusOneScale and PhaseColourScale and threshold and gain
     * are ignored for PhaseColourScale.
     */
    ColourScale(Parameters parameters);
    ~ColourScale();

    ColourScale(const ColourScale &) = default;
    ColourScale &operator=(const ColourScale &) = default;

    /**
     * Return the general type of scale this is.
     */
    ColourScaleType getScale() const;
    
    /**
     * Return a pixel number (in the range 0-255 inclusive)
     * corresponding to the given value.  The pixel 0 is used only for
     * values below the threshold supplied in the constructor. All
     * other values are mapped onto the range 1-255.
     */
    int getPixel(double value) const;

    /**
     * Return the colour for the given pixel number (which must be in
     * the range 0-255). The pixel 0 is always the background
     * colour. Other pixels are mapped taking into account the given
     * colourmap rotation (which is also a value in the range 0-255).
     */
    QColor getColourForPixel(int pixel, int rotation) const;
    
    /**
     * Return the colour corresponding to the given value. This is
     * equivalent to getColourForPixel(getPixel(value), rotation).
     */
    QColor getColour(double value, int rotation) const {
        return getColourForPixel(getPixel(value), rotation);
    }

private:
    Parameters m_params;
    ColourMapper m_mapper;
    double m_mappedMin;
    double m_mappedMax;
    static int m_maxPixel;
};

#endif