125 lines
3.9 KiB
Java
125 lines
3.9 KiB
Java
/*
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* Copyright 2012, 2013 OpenScienceMap
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*
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* This program is free software: you can redistribute it and/or modify it under the
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* terms of the GNU Lesser General Public License as published by the Free Software
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* Foundation, either version 3 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
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* PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License along with
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* this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package org.oscim.utils;
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import android.graphics.Point;
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/**
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* @author Hannes Janetzek
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* taken from http://en.wikipedia.org/wiki/Cohen%E2%80%93
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* Sutherland_algorithm
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*/
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public class LineClipper {
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public static final int INSIDE = 0; // 0000
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public static final int LEFT = 1; // 0001
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public static final int RIGHT = 2; // 0010
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public static final int BOTTOM = 4; // 0100
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public static final int TOP = 8; // 1000
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// Compute the bit code for a point (x, y) using the clip rectangle
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// bounded diagonally by (xmin, ymin), and (xmax, ymax)
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private int xmin, xmax, ymin, ymax;
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public LineClipper(int minx, int miny, int maxx, int maxy) {
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this.xmin = minx;
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this.ymin = miny;
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this.xmax = maxx;
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this.ymax = maxy;
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}
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public boolean clip(Point p1, Point p2) {
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return clip(p1.x, p1.y, p2.x, p2.y);
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}
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public int outCode(int x, int y) {
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int code;
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code = INSIDE; // initialised as being inside of clip window
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if (x < xmin) // to the left of clip window
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code |= LEFT;
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else if (x > xmax) // to the right of clip window
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code |= RIGHT;
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if (y < ymin) // below the clip window
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code |= BOTTOM;
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else if (y > ymax) // above the clip window
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code |= TOP;
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return code;
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}
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// CohenSutherland clipping algorithm clips a line from
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// P0 = (x0, y0) to P1 = (x1, y1) against a rectangle with
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// diagonal from (xmin, ymin) to (xmax, ymax).
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public boolean clip(int x0, int y0, int x1, int y1) {
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// compute outcodes for P0, P1, and whatever point lies outside the clip rectangle
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int outcode0 = outCode(x0, y0);
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int outcode1 = outCode(x1, y1);
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boolean accept = false;
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while (true) {
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if ((outcode0 | outcode1) == 0) { // Bitwise OR is 0. Trivially accept and get out of loop
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accept = true;
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break;
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} else if ((outcode0 & outcode1) != 0) { // Bitwise AND is not 0. Trivially reject and get out of loop
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break;
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} else {
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// failed both tests, so calculate the line segment to clip
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// from an outside point to an intersection with clip edge
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int x = 0;
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int y = 0;
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// At least one endpoint is outside the clip rectangle; pick it.
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int outcodeOut = (outcode0 == 0) ? outcode1 : outcode0;
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// Now find the intersection point;
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// use formulas y = y0 + slope * (x - x0), x = x0 + (1 / slope) * (y - y0)
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if ((outcodeOut & TOP) != 0) { // point is above the clip rectangle
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x = x0 + (x1 - x0) * (ymax - y0) / (y1 - y0);
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y = ymax;
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} else if ((outcodeOut & BOTTOM) != 0) { // point is below the clip rectangle
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x = x0 + (x1 - x0) * (ymin - y0) / (y1 - y0);
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y = ymin;
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} else if ((outcodeOut & RIGHT) != 0) { // point is to the right of clip rectangle
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y = y0 + (y1 - y0) * (xmax - x0) / (x1 - x0);
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x = xmax;
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} else if ((outcodeOut & LEFT) != 0) { // point is to the left of clip rectangle
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y = y0 + (y1 - y0) * (xmin - x0) / (x1 - x0);
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x = xmin;
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}
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// Now we move outside point to intersection point to clip
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// and get ready for next pass.
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if (outcodeOut == outcode0) {
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x0 = x;
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y0 = y;
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outcode0 = outCode(x0, y0);
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} else {
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x1 = x;
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y1 = y;
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outcode1 = outCode(x1, y1);
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}
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}
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}
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// TODO do sth with the result x0...
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return accept;
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}
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}
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