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Replicate the dot-gamma logic in the base/rate guessing code

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This commit is contained in:
Eric Fischer 2015-12-16 13:09:31 -08:00
parent b7a411769a
commit 38fe00c7ab
1 changed files with 36 additions and 1 deletions
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37
geojson.c
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@ -1058,12 +1058,14 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
unsigned x;
unsigned y;
long long count;
double gap;
unsigned long long previndex;
} tile[MAX_ZOOM + 1], max[MAX_ZOOM + 1];
{
int i;
for (i = 0; i <= MAX_ZOOM; i++) {
tile[i].x = tile[i].y = tile[i].count = 0;
tile[i].x = tile[i].y = tile[i].count = tile[i].gap = tile[i].previndex = 0;
max[i].x = max[i].y = max[i].count = 0;
}
}
@ -1082,6 +1084,8 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
yyy = yy >> (32 - z);
}
double scale = (double) (1LL << (64 - 2 * (z + 8)));
if (tile[z].x != xxx || tile[z].y != yyy) {
if (tile[z].count > max[z].count) {
max[z] = tile[z];
@ -1090,6 +1094,37 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
tile[z].x = xxx;
tile[z].y = yyy;
tile[z].count = 0;
tile[z].gap = 0;
tile[z].previndex = 0;
}
// Keep in sync with write_tile()
if (gamma > 0) {
if (tile[z].gap > 0) {
if (map[i].index == tile[z].previndex) {
continue; // Exact duplicate: can't fulfil the gap requirement
}
if (exp(log((map[i].index - tile[z].previndex) / scale) * gamma) >= tile[z].gap) {
// Dot is further from the previous than the nth root of the gap,
// so produce it, and choose a new gap at the next point.
tile[z].gap = 0;
} else {
continue;
}
} else {
tile[z].gap = (map[i].index - tile[z].previndex) / scale;
if (tile[z].gap == 0) {
continue; // Exact duplicate: skip
} else if (tile[z].gap < 1) {
continue; // Narrow dot spacing: need to stretch out
} else {
tile[z].gap = 0; // Wider spacing than minimum: so pass through unchanged
}
}
tile[z].previndex = map[i].index;
}
tile[z].count++;