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// Copyright (c) 2000-2001 Brad Hughes <bhughes@trolltech.com>
//
// Use, modification and distribution is allowed without limitation,
// warranty, or liability of any kind.
//
#include "logscale.h"
#include <math.h>
#include <stdio.h>
LogScale::LogScale(int maxscale, int maxrange)
: indices(0), s(0), r(0)
{
setMax(maxscale, maxrange);
}
LogScale::~LogScale()
{
if (indices)
delete [] indices;
}
void LogScale::setMax(int maxscale, int maxrange)
{
if (maxscale == 0 || maxrange == 0)
return;
s = maxscale;
r = maxrange;
if (indices)
delete [] indices;
double alpha;
int i, scaled;
double domain = double(maxscale),
range = double(maxrange),
x = 1.0,
dx = 1.0,
y = 0.0,
yy = 0.0,
t = 0.0,
e4 = double(1.0E-8);
indices = new int[maxrange];
for (i = 0; i < maxrange; i++)
indices[i] = 0;
// initialize log scale
while (fabs(dx) > e4) {
t = log((domain + x) / x);
y = (x * t) - range;
yy = t - (domain / (x + domain));
dx = y / yy;
x -= dx;
}
alpha = x;
for (i = 1; i < (int) domain; i++) {
scaled = (int) floor(0.5 + (alpha * log((double(i) + alpha) / alpha)));
if (indices[scaled - 1] < i)
indices[scaled - 1] = i;
}
}
int LogScale::operator[](int index)
{
return indices[index];
}
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