move ScanBox to utils
This commit is contained in:
Hannes Janetzek
212
src/org/oscim/utils/ScanBox.java
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212
src/org/oscim/utils/ScanBox.java
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/*
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* Copyright 2012 Hannes Janetzek
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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 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 License for more details.
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*
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* You should have received a copy of the GNU Lesser General 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 org.oscim.core.Tile;
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/**
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* Scan-line fill algorithm to retrieve tile-coordinates.
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*
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* ScanBox is used to calculate tile coordinates that intersect
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* the box (or trapezoid) which is the projection of screen
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* bounds to the map.
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*
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* use:
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* MapViewPosition.getMapViewProjection(box)
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* yourScanBox.scan(pos.x, pos.y, pos.scale, zoomLevel, coords);
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*
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* where zoomLevel is the zoom-level for which tile coordinates
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* should be calculated.
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* */
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public abstract class ScanBox {
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public static void transScale(double x, double y, double scale, int zoom, float[] box){
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scale *= Tile.SIZE;
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//double curScale = Tile.SIZE * scale;
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double div = scale / (1 << zoom);
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x *= scale;
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y *= scale;
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for (int i = 0; i < 8; i += 2) {
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box[i + 0] = (float) ((x + box[i + 0]) / div);
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box[i + 1] = (float) ((y + box[i + 1]) / div);
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}
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}
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/*
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* ported from Polymaps: Layer.js
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*/
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static class Edge {
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float x0, y0, x1, y1, dx, dy;
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void set(float x0, float y0, float x1, float y1) {
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if (y0 <= y1) {
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this.x0 = x0;
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this.y0 = y0;
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this.x1 = x1;
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this.y1 = y1;
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} else {
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this.x0 = x1;
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this.y0 = y1;
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this.x1 = x0;
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this.y1 = y0;
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}
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this.dx = this.x1 - this.x0;
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this.dy = this.y1 - this.y0;
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}
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}
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private Edge ab = new Edge();
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private Edge bc = new Edge();
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private Edge ca = new Edge();
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private int minX, maxX;
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protected int mZoom;
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protected abstract void setVisible(int y, int x1, int x2);
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public void scan(double x, double y, double scale, int zoom, float[] box) {
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mZoom = zoom;
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transScale(x, y, scale, zoom, box);
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// clip result to min/max as steep angles
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// cause overshooting in x direction.
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float max = Float.MIN_VALUE;
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float min = Float.MAX_VALUE;
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for(int i = 0; i < 8; i += 2){
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float xx = box[i];
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if (xx > max)
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max = xx;
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if (xx < min)
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min = xx;
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}
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max = (float)Math.ceil(max);
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min = (float)Math.floor(min);
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if (min == max)
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max++;
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minX = (int) min;
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maxX = (int) max;
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// top-left -> top-right
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ab.set(box[0], box[1], box[2], box[3]);
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// top-right -> bottom-right
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bc.set(box[2], box[3], box[4], box[5]);
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// bottom-right -> bottom-left
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ca.set(box[4], box[5], box[0], box[1]);
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scanTriangle();
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// top-left -> bottom-right
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ab.set(box[0], box[1], box[4], box[5]);
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// bottom-right -> bottom-left
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bc.set(box[4], box[5], box[6], box[7]);
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// bottom-left -> top-left
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ca.set(box[6], box[7], box[0], box[1]);
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scanTriangle();
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}
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private void scanTriangle() {
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// sort so that ca.dy > bc.dy > ab.dy
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if (ab.dy > bc.dy) {
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Edge t = ab;
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ab = bc;
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bc = t;
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}
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if (ab.dy > ca.dy) {
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Edge t = ab;
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ab = ca;
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ca = t;
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}
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if (bc.dy > ca.dy) {
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Edge t = bc;
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bc = ca;
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ca = t;
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}
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// shouldnt be possible, anyway
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if (ca.dy == 0)
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return;
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if (ab.dy > 0.0)
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scanSpans(ca, ab);
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if (bc.dy > 0.0)
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scanSpans(ca, bc);
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}
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private void scanSpans(Edge e0, Edge e1) {
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// scan the y-range of the edge with less dy
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int y0 = (int) Math.max(0, Math.floor(e1.y0));
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int y1 = (int) Math.min((1 << mZoom), Math.ceil(e1.y1));
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// sort edge by x-coordinate
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if (e0.x0 == e1.x0 && e0.y0 == e1.y0) {
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// bottom-flat
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if (e0.x0 + e1.dy / e0.dy * e0.dx < e1.x1) {
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Edge t = e0;
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e0 = e1;
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e1 = t;
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}
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} else {
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// top-flat
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if (e0.x1 - e1.dy / e0.dy * e0.dx < e1.x0) {
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Edge t = e0;
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e0 = e1;
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e1 = t;
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}
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}
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float m0 = e0.dx / e0.dy;
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float m1 = e1.dx / e1.dy;
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// e0 goes to the right, e1 to the left
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int d0 = e0.dx > 0 ? 1 : 0; // use y + 1 to compute x0
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int d1 = e1.dx < 0 ? 1 : 0; // use y + 1 to compute x1
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float dy;
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for (int y = y0; y < y1; y++) {
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dy = d0 + y - e0.y0;
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if (dy > e0.dy)
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dy = e0.dy;
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int x0 = (int)Math.ceil(e0.x0 + m0 * dy);
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dy = d1 + y - e1.y0;
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if (dy > e1.dy)
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dy = e1.dy;
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int x1 = (int)Math.floor(e1.x0 + m1 * dy);
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if (x1 < minX)
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x1 = minX;
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if (x0 > maxX)
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x0 = maxX;
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if (x1 < x0)
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setVisible(y, x1, x0);
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}
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}
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}
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