1 files changed, 74 insertions, 0 deletions
diff --git a/src/logscale.cpp b/src/logscale.cpp
new file mode 100644
index 000000000..921004fd9
--- /dev/null
+++ b/src/logscale.cpp
@@ -0,0 +1,74 @@
+// 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];
+}