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Add an option for the Visvalingam simplification algorithm (#16)

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* First attempt at porting Paul Mach's Visvalingam implementation

* Make indent

* Mostly working

* Approximate equivalence from Douglas-Peucker to Visvalingam levels

* Don't simplify away tile boundary crossing points

* Add a command-line option and test for Visvalingam simplification

* Update changelog

* Cleanup in response to review feedback

* Include <stdio.h> to fix compiler warnings
This commit is contained in:
Erica Fischer
2022-09-30 12:00:07 -07:00
committed by GitHub
parent 6de00c15ec
commit 4ef430b913
11 changed files with 4282 additions and 4 deletions
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geometry.cpp
+12 -1
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@@ -849,8 +849,19 @@ drawvec simplify_lines(drawvec &geom, int z, int detail, bool mark_tile_bounds,
geom[i].necessary = 1;
geom[j - 1].necessary = 1;
// empirical mapping from douglas-peucker simplifications
// to visvalingam simplifications that yield similar
// output sizes
double sim = simplification * (0.1596 * z + 0.878);
double scale = (res * sim) * (res * sim);
scale = exp(1.002 * log(scale) + 0.3043);
if (j - i > 1) {
douglas_peucker(geom, i, j - i, res * simplification, 2, retain);
if (additional[A_VISVALINGAM]) {
visvalingam(geom, i, j, scale, retain);
} else {
douglas_peucker(geom, i, j - i, res * simplification, 2, retain);
}
}
i = j - 1;
}