/*
 * This plugin implements the Edit/Selection/Create Selection command.
 * It is based on a proposal by Tom Larkworthy.
 * Written and public domained in June 2006 by Johannes E. Schindelin
 */
package ij.plugin.filter;
import ij.IJ;
import ij.ImagePlus;
import ij.gui.Roi;
import ij.gui.ShapeRoi;
import ij.process.*;

import java.awt.Polygon;
import java.awt.Rectangle;
import java.awt.geom.Area;
import java.awt.geom.GeneralPath;
import java.util.ArrayList;

public class ThresholdToSelection implements PlugInFilter {
	ImagePlus image;
	ImageProcessor ip;
	float min, max;
	int w, h;
	boolean showStatus;

	public void run(ImageProcessor ip) {
		showStatus = true;
		image.setRoi(convert(ip));
	}
	
	public static Roi run(ImagePlus imp) {
		ThresholdToSelection tts = new ThresholdToSelection();
		tts.image = imp;
		return tts.convert(imp.getProcessor());
	}
	
	public Roi convert(ImageProcessor ip) {
		this.ip = ip;
		min = (float)ip.getMinThreshold();
		max = (float)ip.getMaxThreshold();
		w = ip.getWidth();
		h = ip.getHeight();
		return getRoi();
	}

	final boolean selected(int x, int y) {
		float v = ip.getf(x,y);
		return v>=min && v<=max;
	}

	/*
	 * This class implements a Cartesian polygon in progress.
	 * The edges are supposed to be of unit length, and parallel to
	 * one axis.
	 * It is implemented as a deque to be able to add points to both
	 * sides.
	 * The points should be added such that for each pair of consecutive
	 * points, the inner part is on the left.
	 */
	static class Outline {
		int[] x, y;
		int first, last, reserved;
		final int GROW = 10;

		public Outline() {
			reserved = GROW;
			x = new int[reserved];
			y = new int[reserved];
			first = last = GROW / 2;
		}

		private void needs(int newCount, int offset) {
			if (newCount > reserved || (offset > first)) {
				if (newCount < reserved + GROW + 1)
					newCount = reserved + GROW + 1;
				int[] newX = new int[newCount];
				int[] newY = new int[newCount];
				System.arraycopy(x, 0, newX, offset, last);
				System.arraycopy(y, 0, newY, offset, last);
				x = newX;
				y = newY;
				first += offset;
				last += offset;
				reserved = newCount;
			}
		}

		public void push(int x, int y) {
			needs(last + 1, 0);
			this.x[last] = x;
			this.y[last] = y;
			last++;
		}

		public void shift(int x, int y) {
			needs(last + 1, GROW);
			first--;
			this.x[first] = x;
			this.y[first] = y;
		}

		public void push(Outline o) {
			int count = o.last - o.first;
			needs(last + count, 0);
			System.arraycopy(o.x, o.first, x, last, count);
			System.arraycopy(o.y, o.first, y, last, count);
			last += count;
		}

		public void shift(Outline o) {
			int count = o.last - o.first;
			needs(last + count + GROW, count + GROW);
			first -= count;
			System.arraycopy(o.x, o.first, x, first, count);
			System.arraycopy(o.y, o.first, y, first, count);
		}

		public Polygon getPolygon() {
			// optimize out long straight lines
			int i, j=first+1;
			for (i=first+1; i+1<last; j++) {
				int x1 = x[j] - x[j - 1];
				int y1 = y[j] - y[j - 1];
				int x2 = x[j + 1] - x[j];
				int y2 = y[j + 1] - y[j];
				if (x1 * y2 == x2 * y1) {
					// merge i + 1 into i
					last--;
					continue;
				}
				if (i != j) {
					x[i] = x[j];
					y[i] = y[j];
				}
				i++;
			}
			// wraparound
			int x1 = x[j] - x[j-1];
			int y1 = y[j] - y[j-1];
			int x2 = x[first] - x[j];
			int y2 = y[first] - y[j];
			if (x1*y2==x2*y1)
				last--;
			else {
				x[i] = x[j];
				y[i] = y[j];
			}
			int count = last - first;
			int[] xNew = new int[count];
			int[] yNew = new int[count];
			System.arraycopy(x, first, xNew, 0, count);
			System.arraycopy(y, first, yNew, 0, count);
			return new Polygon(xNew, yNew, count);
		}

		public String toString() {
			String res = "(first:" + first + ",last:" + last +
				",reserved:" + reserved + ":";
			if (last > x.length) System.err.println("ERROR!");
			for (int i = first; i < last && i < x.length; i++)
				res += "(" + x[i] + "," + y[i] + ")";
			return res + ")";
		}
	}

	/*
	 * Construct all outlines simultaneously by traversing the rows
	 * from top to bottom.
	 *
	 * prevRow[x + 1] indicates if the pixel at (x, y - 1) is selected.
	 *
	 * outline[x] is the outline which is currently unclosed at the
	 * lower right corner of the previous row.
	 */
	Roi getRoi() {
		if (showStatus)
			IJ.showStatus("Converting threshold to selection");
		boolean[] prevRow, thisRow;
		ArrayList polygons = new ArrayList();
		Outline[] outline;
		int progressInc = Math.max(h/50, 1);
		
		prevRow = new boolean[w + 2];
		thisRow = new boolean[w + 2];
		outline = new Outline[w + 1];

		for (int y = 0; y <= h; y++) {
			boolean[] b = prevRow; prevRow = thisRow; thisRow = b;
			for (int x = 0; x <= w; x++) {
				if (y < h && x < w)
					thisRow[x + 1] = selected(x, y);
				else
					thisRow[x + 1] = false;
				if (thisRow[x + 1]) {
					if (!prevRow[x + 1]) {
						// upper edge:
						// - left and right are null: new outline
						// - left null: push
						// - right null: shift
						// - left == right: close
						// - left != right: merge
						if (outline[x] == null) {
							if (outline[x + 1] == null) {
								outline[x + 1] = outline[x] = new Outline();
								outline[x].push(x + 1, y);
								outline[x].push(x, y);
							} else {
								outline[x] = outline[x + 1];
								outline[x + 1] = null;
								outline[x].push(x, y);
							}
						} else {
							if (outline[x + 1] == null) {
								outline[x + 1] = outline[x];
								outline[x] = null;
								outline[x + 1].shift(x + 1, y);
							} else if (outline[x + 1] == outline[x]) {
								//System.err.println("subtract " + outline[x]);
								polygons.add(outline[x].getPolygon()); // MINUS
								outline[x] = outline[x + 1] = null;
							} else {
								outline[x].shift(outline[x + 1]);
								for (int x1 = 0; x1 <= w; x1++)
									if (x1 != x + 1 && outline[x1] == outline[x + 1]) {
										outline[x1] = outline[x];
										outline[x] = outline[x + 1] = null;
										break;
									}
								if (outline[x] != null)
									throw new RuntimeException("assertion failed");
							}
						}
					}
					if (!thisRow[x]) {
						// left edge
						if (outline[x] == null)
							throw new RuntimeException("assertion failed!");
						outline[x].push(x, y + 1);
					}
				} else {
					if (prevRow[x + 1]) {
						// lower edge
						// - bot null: new outline
						// - left == null: shift
						// - right == null: push
						// - right == left: close
						// - right != left: push
						if (outline[x] == null) {
							if (outline[x + 1] == null) {
								outline[x] = outline[x + 1] = new Outline();
								outline[x].push(x, y);
								outline[x].push(x + 1, y);
							} else {
								outline[x] = outline[x + 1];
								outline[x + 1] = null;
								outline[x].shift(x, y);
							}
						} else if (outline[x + 1] == null) {
							outline[x + 1] = outline[x];
							outline[x] = null;
							outline[x + 1].push(x + 1, y);
						} else if (outline[x + 1] == outline[x]) {
							//System.err.println("add " + outline[x]);
							polygons.add(outline[x].getPolygon()); // PLUS
							outline[x] = outline[x + 1] = null;
						} else {
							outline[x].push(outline[x + 1]);
							for (int x1 = 0; x1 <= w; x1++)
								if (x1 != x + 1 && outline[x1] == outline[x + 1]) {
									outline[x1] = outline[x];
									outline[x] = outline[x + 1] = null;
									break;
								}
							if (outline[x] != null)
								throw new RuntimeException("assertion failed");
						}
					}
					if (thisRow[x]) {
						// right edge
						if (outline[x] == null)
							throw new RuntimeException("assertion failed");
						outline[x].shift(x, y + 1);
					}
				}
			}
			if (showStatus && (y&progressInc)==0)
				IJ.showProgress(y + 1, h + 1);
		}

		//IJ.showStatus("Creating GeneralPath");
		GeneralPath path = new GeneralPath(GeneralPath.WIND_EVEN_ODD);
		for (int i = 0; i < polygons.size(); i++)
			path.append((Polygon)polygons.get(i), false);

		ShapeRoi shape = new ShapeRoi(path);
		Roi roi = shape!=null?shape.shapeToRoi():null; // try to convert to non-composite ROI
		if (showStatus)
			IJ.showProgress(1,1);
		if (roi!=null)
			return roi;
		else
			return shape;
	}

	public int setup(String arg, ImagePlus imp) {
		image = imp;
		return DOES_8G | DOES_16 | DOES_32 | NO_CHANGES;
	}
}

