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Add Hilbert Curve feature sequencing as an option

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This commit is contained in:
Eric Fischer
2018-12-12 10:51:00 -08:00
parent 5f1c0e151f
commit 6376c283ba
10 changed files with 9842 additions and 20 deletions
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projection.cpp
+58 -2
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@@ -5,6 +5,9 @@
#include <atomic>
#include "projection.hpp"
unsigned long long (*encode_index)(unsigned int wx, unsigned int wy) = NULL;
void (*decode_index)(unsigned long long index, unsigned *wx, unsigned *wy) = NULL;
struct projection projections[] = {
{"EPSG:4326", lonlat2tile, tile2lonlat, "urn:ogc:def:crs:OGC:1.3:CRS84"},
{"EPSG:3857", epsg3857totile, tiletoepsg3857, "urn:ogc:def:crs:EPSG::3857"},
@@ -93,7 +96,60 @@ void tiletoepsg3857(long long ix, long long iy, int zoom, double *ox, double *oy
*oy = ((1LL << 32) - 1 - iy - (1LL << 31)) * M_PI * 6378137.0 / (1LL << 31);
}
unsigned long long encode(unsigned int wx, unsigned int wy) {
// https://en.wikipedia.org/wiki/Hilbert_curve
void hilbert_rot(unsigned long long n, unsigned *x, unsigned *y, unsigned long long rx, unsigned long long ry) {
if (ry == 0) {
if (rx == 1) {
*x = n - 1 - *x;
*y = n - 1 - *y;
}
unsigned t = *x;
*x = *y;
*y = t;
}
}
unsigned long long hilbert_xy2d(unsigned long long n, unsigned x, unsigned y) {
unsigned long long d = 0;
unsigned long long rx, ry;
for (unsigned long long s = n / 2; s > 0; s /= 2) {
rx = (x & s) != 0;
ry = (y & s) != 0;
d += s * s * ((3 * rx) ^ ry);
hilbert_rot(s, &x, &y, rx, ry);
}
return d;
}
void hilbert_d2xy(unsigned long long n, unsigned long long d, unsigned *x, unsigned *y) {
unsigned long long rx, ry;
unsigned long long t = d;
*x = *y = 0;
for (unsigned long long s = 1; s < n; s *= 2) {
rx = 1 & (t / 2);
ry = 1 & (t ^ rx);
hilbert_rot(s, x, y, rx, ry);
*x += s * rx;
*y += s * ry;
t /= 4;
}
}
unsigned long long encode_hilbert(unsigned int wx, unsigned int wy) {
return hilbert_xy2d(1LL << 32, wx, wy);
}
void decode_hilbert(unsigned long long index, unsigned *wx, unsigned *wy) {
hilbert_d2xy(1LL << 32, index, wx, wy);
}
unsigned long long encode_quadkey(unsigned int wx, unsigned int wy) {
unsigned long long out = 0;
int i;
@@ -111,7 +167,7 @@ unsigned long long encode(unsigned int wx, unsigned int wy) {
static std::atomic<unsigned char> decodex[256];
static std::atomic<unsigned char> decodey[256];
void decode(unsigned long long index, unsigned *wx, unsigned *wy) {
void decode_quadkey(unsigned long long index, unsigned *wx, unsigned *wy) {
static std::atomic<int> initialized(0);
if (!initialized) {
for (size_t ix = 0; ix < 256; ix++) {