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| // Based on simplify-js https://github.com/mourner/simplify-js
// Copyright (c) 2012, Vladimir Agafonkin
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
goog.provide('ol.geom.flat.simplify');
goog.require('ol.math');
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {number} end End.
* @param {number} stride Stride.
* @param {number} squaredTolerance Squared tolerance.
* @param {boolean} highQuality Highest quality.
* @param {Array.<number>=} opt_simplifiedFlatCoordinates Simplified flat
* coordinates.
* @return {Array.<number>} Simplified line string.
*/
ol.geom.flat.simplify.lineString = function(flatCoordinates, offset, end,
stride, squaredTolerance, highQuality, opt_simplifiedFlatCoordinates) {
var simplifiedFlatCoordinates = opt_simplifiedFlatCoordinates !== undefined ?
opt_simplifiedFlatCoordinates : [];
if (!highQuality) {
end = ol.geom.flat.simplify.radialDistance(flatCoordinates, offset, end,
stride, squaredTolerance,
simplifiedFlatCoordinates, 0);
flatCoordinates = simplifiedFlatCoordinates;
offset = 0;
stride = 2;
}
simplifiedFlatCoordinates.length = ol.geom.flat.simplify.douglasPeucker(
flatCoordinates, offset, end, stride, squaredTolerance,
simplifiedFlatCoordinates, 0);
return simplifiedFlatCoordinates;
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {number} end End.
* @param {number} stride Stride.
* @param {number} squaredTolerance Squared tolerance.
* @param {Array.<number>} simplifiedFlatCoordinates Simplified flat
* coordinates.
* @param {number} simplifiedOffset Simplified offset.
* @return {number} Simplified offset.
*/
ol.geom.flat.simplify.douglasPeucker = function(flatCoordinates, offset, end,
stride, squaredTolerance, simplifiedFlatCoordinates, simplifiedOffset) {
var n = (end - offset) / stride;
if (n < 3) {
for (; offset < end; offset += stride) {
simplifiedFlatCoordinates[simplifiedOffset++] =
flatCoordinates[offset];
simplifiedFlatCoordinates[simplifiedOffset++] =
flatCoordinates[offset + 1];
}
return simplifiedOffset;
}
/** @type {Array.<number>} */
var markers = new Array(n);
markers[0] = 1;
markers[n - 1] = 1;
/** @type {Array.<number>} */
var stack = [offset, end - stride];
var index = 0;
var i;
while (stack.length > 0) {
var last = stack.pop();
var first = stack.pop();
var maxSquaredDistance = 0;
var x1 = flatCoordinates[first];
var y1 = flatCoordinates[first + 1];
var x2 = flatCoordinates[last];
var y2 = flatCoordinates[last + 1];
for (i = first + stride; i < last; i += stride) {
var x = flatCoordinates[i];
var y = flatCoordinates[i + 1];
var squaredDistance = ol.math.squaredSegmentDistance(
x, y, x1, y1, x2, y2);
if (squaredDistance > maxSquaredDistance) {
index = i;
maxSquaredDistance = squaredDistance;
}
}
if (maxSquaredDistance > squaredTolerance) {
markers[(index - offset) / stride] = 1;
if (first + stride < index) {
stack.push(first, index);
}
if (index + stride < last) {
stack.push(index, last);
}
}
}
for (i = 0; i < n; ++i) {
if (markers[i]) {
simplifiedFlatCoordinates[simplifiedOffset++] =
flatCoordinates[offset + i * stride];
simplifiedFlatCoordinates[simplifiedOffset++] =
flatCoordinates[offset + i * stride + 1];
}
}
return simplifiedOffset;
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {Array.<number>} ends Ends.
* @param {number} stride Stride.
* @param {number} squaredTolerance Squared tolerance.
* @param {Array.<number>} simplifiedFlatCoordinates Simplified flat
* coordinates.
* @param {number} simplifiedOffset Simplified offset.
* @param {Array.<number>} simplifiedEnds Simplified ends.
* @return {number} Simplified offset.
*/
ol.geom.flat.simplify.douglasPeuckers = function(flatCoordinates, offset,
ends, stride, squaredTolerance, simplifiedFlatCoordinates,
simplifiedOffset, simplifiedEnds) {
var i, ii;
for (i = 0, ii = ends.length; i < ii; ++i) {
var end = ends[i];
simplifiedOffset = ol.geom.flat.simplify.douglasPeucker(
flatCoordinates, offset, end, stride, squaredTolerance,
simplifiedFlatCoordinates, simplifiedOffset);
simplifiedEnds.push(simplifiedOffset);
offset = end;
}
return simplifiedOffset;
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {Array.<Array.<number>>} endss Endss.
* @param {number} stride Stride.
* @param {number} squaredTolerance Squared tolerance.
* @param {Array.<number>} simplifiedFlatCoordinates Simplified flat
* coordinates.
* @param {number} simplifiedOffset Simplified offset.
* @param {Array.<Array.<number>>} simplifiedEndss Simplified endss.
* @return {number} Simplified offset.
*/
ol.geom.flat.simplify.douglasPeuckerss = function(
flatCoordinates, offset, endss, stride, squaredTolerance,
simplifiedFlatCoordinates, simplifiedOffset, simplifiedEndss) {
var i, ii;
for (i = 0, ii = endss.length; i < ii; ++i) {
var ends = endss[i];
var simplifiedEnds = [];
simplifiedOffset = ol.geom.flat.simplify.douglasPeuckers(
flatCoordinates, offset, ends, stride, squaredTolerance,
simplifiedFlatCoordinates, simplifiedOffset, simplifiedEnds);
simplifiedEndss.push(simplifiedEnds);
offset = ends[ends.length - 1];
}
return simplifiedOffset;
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {number} end End.
* @param {number} stride Stride.
* @param {number} squaredTolerance Squared tolerance.
* @param {Array.<number>} simplifiedFlatCoordinates Simplified flat
* coordinates.
* @param {number} simplifiedOffset Simplified offset.
* @return {number} Simplified offset.
*/
ol.geom.flat.simplify.radialDistance = function(flatCoordinates, offset, end,
stride, squaredTolerance, simplifiedFlatCoordinates, simplifiedOffset) {
if (end <= offset + stride) {
// zero or one point, no simplification possible, so copy and return
for (; offset < end; offset += stride) {
simplifiedFlatCoordinates[simplifiedOffset++] = flatCoordinates[offset];
simplifiedFlatCoordinates[simplifiedOffset++] =
flatCoordinates[offset + 1];
}
return simplifiedOffset;
}
var x1 = flatCoordinates[offset];
var y1 = flatCoordinates[offset + 1];
// copy first point
simplifiedFlatCoordinates[simplifiedOffset++] = x1;
simplifiedFlatCoordinates[simplifiedOffset++] = y1;
var x2 = x1;
var y2 = y1;
for (offset += stride; offset < end; offset += stride) {
x2 = flatCoordinates[offset];
y2 = flatCoordinates[offset + 1];
if (ol.math.squaredDistance(x1, y1, x2, y2) > squaredTolerance) {
// copy point at offset
simplifiedFlatCoordinates[simplifiedOffset++] = x2;
simplifiedFlatCoordinates[simplifiedOffset++] = y2;
x1 = x2;
y1 = y2;
}
}
if (x2 != x1 || y2 != y1) {
// copy last point
simplifiedFlatCoordinates[simplifiedOffset++] = x2;
simplifiedFlatCoordinates[simplifiedOffset++] = y2;
}
return simplifiedOffset;
};
/**
* @param {number} value Value.
* @param {number} tolerance Tolerance.
* @return {number} Rounded value.
*/
ol.geom.flat.simplify.snap = function(value, tolerance) {
return tolerance * Math.round(value / tolerance);
};
/**
* Simplifies a line string using an algorithm designed by Tim Schaub.
* Coordinates are snapped to the nearest value in a virtual grid and
* consecutive duplicate coordinates are discarded. This effectively preserves
* topology as the simplification of any subsection of a line string is
* independent of the rest of the line string. This means that, for examples,
* the common edge between two polygons will be simplified to the same line
* string independently in both polygons. This implementation uses a single
* pass over the coordinates and eliminates intermediate collinear points.
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {number} end End.
* @param {number} stride Stride.
* @param {number} tolerance Tolerance.
* @param {Array.<number>} simplifiedFlatCoordinates Simplified flat
* coordinates.
* @param {number} simplifiedOffset Simplified offset.
* @return {number} Simplified offset.
*/
ol.geom.flat.simplify.quantize = function(flatCoordinates, offset, end, stride,
tolerance, simplifiedFlatCoordinates, simplifiedOffset) {
// do nothing if the line is empty
if (offset == end) {
return simplifiedOffset;
}
// snap the first coordinate (P1)
var x1 = ol.geom.flat.simplify.snap(flatCoordinates[offset], tolerance);
var y1 = ol.geom.flat.simplify.snap(flatCoordinates[offset + 1], tolerance);
offset += stride;
// add the first coordinate to the output
simplifiedFlatCoordinates[simplifiedOffset++] = x1;
simplifiedFlatCoordinates[simplifiedOffset++] = y1;
// find the next coordinate that does not snap to the same value as the first
// coordinate (P2)
var x2, y2;
do {
x2 = ol.geom.flat.simplify.snap(flatCoordinates[offset], tolerance);
y2 = ol.geom.flat.simplify.snap(flatCoordinates[offset + 1], tolerance);
offset += stride;
if (offset == end) {
// all coordinates snap to the same value, the line collapses to a point
// push the last snapped value anyway to ensure that the output contains
// at least two points
// FIXME should we really return at least two points anyway?
simplifiedFlatCoordinates[simplifiedOffset++] = x2;
simplifiedFlatCoordinates[simplifiedOffset++] = y2;
return simplifiedOffset;
}
} while (x2 == x1 && y2 == y1);
while (offset < end) {
var x3, y3;
// snap the next coordinate (P3)
x3 = ol.geom.flat.simplify.snap(flatCoordinates[offset], tolerance);
y3 = ol.geom.flat.simplify.snap(flatCoordinates[offset + 1], tolerance);
offset += stride;
// skip P3 if it is equal to P2
if (x3 == x2 && y3 == y2) {
continue;
}
// calculate the delta between P1 and P2
var dx1 = x2 - x1;
var dy1 = y2 - y1;
// calculate the delta between P3 and P1
var dx2 = x3 - x1;
var dy2 = y3 - y1;
// if P1, P2, and P3 are colinear and P3 is further from P1 than P2 is from
// P1 in the same direction then P2 is on the straight line between P1 and
// P3
if ((dx1 * dy2 == dy1 * dx2) &&
((dx1 < 0 && dx2 < dx1) || dx1 == dx2 || (dx1 > 0 && dx2 > dx1)) &&
((dy1 < 0 && dy2 < dy1) || dy1 == dy2 || (dy1 > 0 && dy2 > dy1))) {
// discard P2 and set P2 = P3
x2 = x3;
y2 = y3;
continue;
}
// either P1, P2, and P3 are not colinear, or they are colinear but P3 is
// between P3 and P1 or on the opposite half of the line to P2. add P2,
// and continue with P1 = P2 and P2 = P3
simplifiedFlatCoordinates[simplifiedOffset++] = x2;
simplifiedFlatCoordinates[simplifiedOffset++] = y2;
x1 = x2;
y1 = y2;
x2 = x3;
y2 = y3;
}
// add the last point (P2)
simplifiedFlatCoordinates[simplifiedOffset++] = x2;
simplifiedFlatCoordinates[simplifiedOffset++] = y2;
return simplifiedOffset;
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {Array.<number>} ends Ends.
* @param {number} stride Stride.
* @param {number} tolerance Tolerance.
* @param {Array.<number>} simplifiedFlatCoordinates Simplified flat
* coordinates.
* @param {number} simplifiedOffset Simplified offset.
* @param {Array.<number>} simplifiedEnds Simplified ends.
* @return {number} Simplified offset.
*/
ol.geom.flat.simplify.quantizes = function(
flatCoordinates, offset, ends, stride,
tolerance,
simplifiedFlatCoordinates, simplifiedOffset, simplifiedEnds) {
var i, ii;
for (i = 0, ii = ends.length; i < ii; ++i) {
var end = ends[i];
simplifiedOffset = ol.geom.flat.simplify.quantize(
flatCoordinates, offset, end, stride,
tolerance,
simplifiedFlatCoordinates, simplifiedOffset);
simplifiedEnds.push(simplifiedOffset);
offset = end;
}
return simplifiedOffset;
};
/**
* @param {Array.<number>} flatCoordinates Flat coordinates.
* @param {number} offset Offset.
* @param {Array.<Array.<number>>} endss Endss.
* @param {number} stride Stride.
* @param {number} tolerance Tolerance.
* @param {Array.<number>} simplifiedFlatCoordinates Simplified flat
* coordinates.
* @param {number} simplifiedOffset Simplified offset.
* @param {Array.<Array.<number>>} simplifiedEndss Simplified endss.
* @return {number} Simplified offset.
*/
ol.geom.flat.simplify.quantizess = function(
flatCoordinates, offset, endss, stride,
tolerance,
simplifiedFlatCoordinates, simplifiedOffset, simplifiedEndss) {
var i, ii;
for (i = 0, ii = endss.length; i < ii; ++i) {
var ends = endss[i];
var simplifiedEnds = [];
simplifiedOffset = ol.geom.flat.simplify.quantizes(
flatCoordinates, offset, ends, stride,
tolerance,
simplifiedFlatCoordinates, simplifiedOffset, simplifiedEnds);
simplifiedEndss.push(simplifiedEnds);
offset = ends[ends.length - 1];
}
return simplifiedOffset;
};
|