private static long xy2d(long n, long x, long y)
{
long num = 0;
long n1 = n / 2L;
while (n1 > 0L)
{
long rx = (x & n1) > 0L ? 1L : 0L;
long ry = (y & n1) > 0L ? 1L : 0L;
num += n1 * n1 * (3L * rx ^ ry);
HilbertCurve.rot(n1, ref x, ref y, rx, ry);
n1 /= 2L;
}
return(num);
}
public static long HilbertDistance(float latitude, float longitude, long n)
{
long x = (long)(((double)longitude + 180.0) / 360.0 * (double)n);
if (x >= n)
{
x = n - 1L;
}
long y = (long)(((double)latitude + 90.0) / 180.0 * (double)n);
if (y >= n)
{
y = n - 1L;
}
return(HilbertCurve.xy2d(n, x, y));
}
private static void d2xy(long n, long d, out long x, long y)
{
long num = d;
x = y = 0L;
long n1 = 1;
while (n1 < n)
{
long rx = 1L & num / 2L;
long ry = 1L & (num ^ rx);
HilbertCurve.rot(n1, ref x, ref y, rx, ry);
x = x + n1 * rx;
y += n1 * ry;
num /= 4L;
n1 *= 2L;
}
}
// DISCLAIMER: some of this stuff is straight from wikipedia:
// http://en.wikipedia.org/wiki/Hilbert_curve#Applications_and_mapping_algorithms
/// <summary>
/// Calculates hilbert distance.
/// </summary>
/// <returns></returns>
public static long HilbertDistance(float latitude, float longitude, long n)
{
// calculate x, y.
var x = (long)((((double)longitude + 180.0) / 360.0) * n);
if (x >= n)
{
x = n - 1;
}
var y = (long)((((double)latitude + 90.0) / 180.0) * n);
if (y >= n)
{
y = n - 1;
}
// calculate hilbert value for x-y and n.
return(HilbertCurve.xy2d(n, x, y));
}
/// <summary>
/// Calculates all distinct hilbert distances inside of the given bounding box.
/// </summary>
/// <returns></returns>
public static List <long> HilbertDistances(float minLatitude, float minLongitude,
float maxLatitude, float maxLongitude, long n)
{
var deltaLat = 180.0f / n;
var deltaLon = 360.0f / n;
var distances = new List <long>((int)(
((maxLatitude - minLatitude) / deltaLat) *
((maxLongitude - minLongitude) / deltaLon)));
minLatitude = System.Math.Max(minLatitude - deltaLat, -90);
minLongitude = System.Math.Max(minLongitude - deltaLon, -180);
maxLatitude = System.Math.Min(maxLatitude + deltaLat, 90);
maxLongitude = System.Math.Min(maxLongitude + deltaLon, 180);
for (var latitude = minLatitude; latitude < maxLatitude; latitude = latitude + deltaLat)
{
for (var longitude = minLongitude; longitude < maxLongitude; longitude = longitude + deltaLon)
{
distances.Add(HilbertCurve.HilbertDistance(latitude, longitude, n));
}
}
return(distances);
}
public static List <long> HilbertDistances(float minLatitude, float minLongitude, float maxLatitude, float maxLongitude, long n)
{
float num1 = 180f / (float)n;
float num2 = 360f / (float)n;
List <long> longList = new List <long>((int)(((double)maxLatitude - (double)minLatitude) / (double)num1 * (((double)maxLongitude - (double)minLongitude) / (double)num2)));
minLatitude = System.Math.Max(minLatitude - num1, -90f);
minLongitude = System.Math.Max(minLongitude - num2, -180f);
maxLatitude = System.Math.Min(maxLatitude + num1, 90f);
maxLongitude = System.Math.Min(maxLongitude + num2, 180f);
float latitude = minLatitude;
while ((double)latitude < (double)maxLatitude)
{
float longitude = minLongitude;
while ((double)longitude < (double)maxLongitude)
{
longList.Add(HilbertCurve.HilbertDistance(latitude, longitude, n));
longitude += num2;
}
latitude += num1;
}
return(longList);
}
