/*
* Copyright 2013 Hannes Janetzek
*
* This file is part of the OpenScienceMap project (http://www.opensciencemap.org).
*
* This program is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
* PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License along with
* this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.oscim.utils.geom;
import org.oscim.core.GeometryBuffer;
/**
* Clip polygons and lines to a rectangle. Output cannot expected to be valid
* Simple-Feature geometry, i.e. all polygon rings are clipped independently
* so that inner and outer rings might touch, etc.
*
* based on http://www.cs.rit.edu/~icss571/clipTrans/PolyClipBack.html
*/
public class TileClipper {
private float xmin;
private float xmax;
private float ymin;
private float ymax;
public TileClipper(float xmin, float ymin, float xmax, float ymax) {
this.xmin = xmin;
this.ymin = ymin;
this.xmax = xmax;
this.ymax = ymax;
mLineClipper = new LineClipper(xmin, ymin, xmax, ymax);
}
public void setRect(float xmin, float ymin, float xmax, float ymax) {
this.xmin = xmin;
this.ymin = ymin;
this.xmax = xmax;
this.ymax = ymax;
mLineClipper.setRect(xmin, ymin, xmax, ymax);
}
private final LineClipper mLineClipper;
private final GeometryBuffer mGeomOut = new GeometryBuffer(10, 1);
public boolean clip(GeometryBuffer geom) {
if (geom.isPoly()) {
GeometryBuffer out = mGeomOut;
out.clear();
clipEdge(geom, out, LineClipper.LEFT);
geom.clear();
clipEdge(out, geom, LineClipper.TOP);
out.clear();
clipEdge(geom, out, LineClipper.RIGHT);
geom.clear();
clipEdge(out, geom, LineClipper.BOTTOM);
if ((geom.indexPos == 0) && (geom.index[0] < 6))
return false;
}
else if (geom.isLine()) {
GeometryBuffer out = mGeomOut;
out.clear();
int numLines = mLineClipper.clipLine(geom, out);
int idx[] = geom.ensureIndexSize(numLines + 1, false);
System.arraycopy(out.index, 0, idx, 0, numLines);
geom.index[numLines] = -1;
float pts[] = geom.ensurePointSize(out.pointPos >> 1, false);
System.arraycopy(out.points, 0, pts, 0, out.pointPos);
geom.indexPos = out.indexPos;
geom.pointPos = out.pointPos;
if ((geom.indexPos == 0) && (geom.index[0] < 4))
return false;
}
return true;
}
private boolean clipEdge(GeometryBuffer in, GeometryBuffer out, int edge) {
out.startPolygon();
boolean outer = true;
int pointPos = 0;
for (int indexPos = 0, n = in.index.length; indexPos < n; indexPos++) {
int len = in.index[indexPos];
if (len < 0)
break;
if (len == 0) {
out.startPolygon();
outer = true;
continue;
}
if (len < 6) {
pointPos += len;
continue;
}
if (!outer)
out.startHole();
switch (edge) {
case LineClipper.LEFT:
clipRingLeft(indexPos, pointPos, in, out);
break;
case LineClipper.RIGHT:
clipRingRight(indexPos, pointPos, in, out);
break;
case LineClipper.TOP:
clipRingTop(indexPos, pointPos, in, out);
break;
case LineClipper.BOTTOM:
clipRingBottom(indexPos, pointPos, in, out);
break;
}
//if (out.index[i] < 6) {
// out.index[i] = 0;
// //if (out.indexPos > 0)
// // out.indexPos--;
// // TODO if outer skip holes
//}
pointPos += len;
outer = false;
}
return true;
}
private void clipRingLeft(int indexPos, int pointPos, GeometryBuffer in, GeometryBuffer out) {
int end = in.index[indexPos] + pointPos;
float px = in.points[end - 2];
float py = in.points[end - 1];
for (int i = pointPos; i < end;) {
float cx = in.points[i++];
float cy = in.points[i++];
if (cx > xmin) {
/* current is inside */
if (px > xmin) {
/* previous was inside */
out.addPoint(cx, cy);
} else {
/* previous was outside, add edge point */
out.addPoint(xmin, py + (cy - py) * (xmin - px) / (cx - px));
out.addPoint(cx, cy);
}
} else {
if (px > xmin) {
/* previous was inside, add edge point */
out.addPoint(xmin, py + (cy - py) * (xmin - px) / (cx - px));
}
/* else skip point */
}
px = cx;
py = cy;
}
}
private void clipRingRight(int indexPos, int pointPos, GeometryBuffer in, GeometryBuffer out) {
int len = in.index[indexPos] + pointPos;
float px = in.points[len - 2];
float py = in.points[len - 1];
for (int i = pointPos; i < len;) {
float cx = in.points[i++];
float cy = in.points[i++];
if (cx < xmax) {
if (px < xmax) {
out.addPoint(cx, cy);
} else {
out.addPoint(xmax, py + (cy - py) * (xmax - px) / (cx - px));
out.addPoint(cx, cy);
}
} else {
if (px < xmax) {
out.addPoint(xmax, py + (cy - py) * (xmax - px) / (cx - px));
}
}
px = cx;
py = cy;
}
}
private void clipRingTop(int indexPos, int pointPos, GeometryBuffer in, GeometryBuffer out) {
int len = in.index[indexPos] + pointPos;
float px = in.points[len - 2];
float py = in.points[len - 1];
for (int i = pointPos; i < len;) {
float cx = in.points[i++];
float cy = in.points[i++];
if (cy < ymax) {
if (py < ymax) {
out.addPoint(cx, cy);
} else {
out.addPoint(px + (cx - px) * (ymax - py) / (cy - py), ymax);
out.addPoint(cx, cy);
}
} else {
if (py < ymax) {
out.addPoint(px + (cx - px) * (ymax - py) / (cy - py), ymax);
}
}
px = cx;
py = cy;
}
}
private void clipRingBottom(int indexPos, int pointPos, GeometryBuffer in, GeometryBuffer out) {
int len = in.index[indexPos] + pointPos;
float px = in.points[len - 2];
float py = in.points[len - 1];
for (int i = pointPos; i < len;) {
float cx = in.points[i++];
float cy = in.points[i++];
if (cy > ymin) {
if (py > ymin) {
out.addPoint(cx, cy);
} else {
out.addPoint(px + (cx - px) * (ymin - py) / (cy - py), ymin);
out.addPoint(cx, cy);
}
} else {
if (py > ymin) {
out.addPoint(px + (cx - px) * (ymin - py) / (cy - py), ymin);
}
}
px = cx;
py = cy;
}
}
}