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#include "colorscale.h"
#include <cmath>
const float EPSILON = 1e-3f;
ColorScale::ColorScale(const QColor &firstColor, const QColor &lastColor)
: m_colors{{firstColor, lastColor}}
{
setExtents(0, 1);
}
ColorScale::ColorScale(std::initializer_list<QColor> colors)
: m_colors(colors)
{
setExtents(0, 1);
}
ColorScale::ColorScale(const QList<QColor> &colors)
: m_colors(colors)
{
setExtents(0, 1);
}
ColorScale::~ColorScale()
{
}
void ColorScale::setExtents(float min, float max)
{
if (min >= max) {
return;
}
m_min = min;
m_max = max;
}
QColor ColorScale::lerp(const QColor &c1, const QColor &c2, float _t)
{
qreal r1, g1, b1, a1;
qreal r2, g2, b2, a2;
qreal t = _t;
c1.getRgbF(&r1, &g1, &b1, &a1);
c2.getRgbF(&r2, &g2, &b2, &a2);
QColor color;
color.setRgbF(r1 * (1 - t) + r2 * t,
g1 * (1 - t) + g2 * t,
b1 * (1 - t) + b2 * t,
a1 * (1 - t) + a2 * t);
return color;
}
QColor ColorScale::color(float t) const
{
if (t < m_min || t > m_max) {
return QColor();
}
// normalize t
t = (t - m_min) / (m_max - m_min);
// two colors, use a simpler solution
if (m_colors.size() == 2) {
return lerp(m_colors.first(), m_colors.last(), t);
}
if (fabs(t - m_min) < EPSILON) {
return m_colors.first();
}
if (fabs(t - m_max) < EPSILON) {
return m_colors.last();
}
// find which colors in the scale are adjacent to ours
int i = int(t * m_colors.size());
int j = i + 1;
if (i >= m_colors.size() - 1) {
return QColor(m_colors.last());
}
// normalize t between the two colors
float step = 1.0f / m_colors.size();
t = (t - i*step) / (j*step - i*step);
return lerp(m_colors[i], m_colors[j], t);
}
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