Nuclex.Support/Source/Packing/CygonRectanglePacker.cs

284 lines
12 KiB
C#

#region CPL License
/*
Nuclex Framework
Copyright (C) 2002-2007 Nuclex Development Labs
This library is free software; you can redistribute it and/or
modify it under the terms of the IBM Common Public License as
published by the IBM Corporation; either version 1.0 of the
License, or (at your option) any later version.
This library 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
IBM Common Public License for more details.
You should have received a copy of the IBM Common Public
License along with this library
*/
#endregion
using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
namespace Nuclex.Support.Packing {
/// <summary>Packer using a custom algorithm by Markus 'Cygon' Ewald</summary>
/// <remarks>
/// <para>
/// Algorithm conceived by Markus Ewald (cygon at nuclex dot org), though
/// I'm quite sure I'm not the first one to come up with it :)
/// </para>
/// <para>
/// The algorithm always places rectangles as low as possible in the packing
/// area. So, for any new rectangle that is to be added, the packer has to
/// determine the X coordinate at which the rectangle can have the lowest
/// overall height without intersecting any other rectangles.
/// </para>
/// <para>
/// To quickly discover these locations, the packer uses a sophisticated
/// data structure that stores the upper silhouette of the packing area. When
/// a new rectangle needs to be added, only the silouette edges need to be
/// analyzed to find the position where the rectangle would achieve the lowest
/// placement possible in the packing area.
/// </para>
/// </remarks>
public class CygonRectanglePacker : RectanglePacker {
#region class SliceStartComparer
/// <summary>Compares the starting position of height slices</summary>
private class SliceStartComparer : IComparer<Point> {
/// <summary>Provides a default instance for the anchor rank comparer</summary>
public static SliceStartComparer Default = new SliceStartComparer();
/// <summary>Compares the starting position of two height slices</summary>
/// <param name="left">Left slice start that will be compared</param>
/// <param name="right">Right slice start that will be compared</param>
/// <returns>The relation of the two slice starts ranks to each other</returns>
public int Compare(Point left, Point right) {
return left.X - right.X;
}
}
#endregion
/// <summary>Initializes a new rectangle packer</summary>
/// <param name="packingAreaWidth">Maximum width of the packing area</param>
/// <param name="packingAreaHeight">Maximum height of the packing area</param>
public CygonRectanglePacker(int packingAreaWidth, int packingAreaHeight)
: base(packingAreaWidth, packingAreaHeight) {
this.heightSlices = new List<Point>();
// At the beginning, the packing area is a single slice of height 0
this.heightSlices.Add(new Point(0, 0));
}
/// <summary>Tries to allocate space for a rectangle in the packing area</summary>
/// <param name="rectangleWidth">Width of the rectangle to allocate</param>
/// <param name="rectangleHeight">Height of the rectangle to allocate</param>
/// <param name="placement">Output parameter receiving the rectangle's placement</param>
/// <returns>True if space for the rectangle could be allocated</returns>
public override bool TryPack(
int rectangleWidth, int rectangleHeight, out Point placement
) {
// If the rectangle is larger than the packing area in any dimension,
// it will never fit!
if(
(rectangleWidth > PackingAreaWidth) || (rectangleHeight > PackingAreaHeight)
) {
placement = Point.Zero;
return false;
}
// Determine the placement for the new rectangle
bool fits = tryFindBestPlacement(rectangleWidth, rectangleHeight, out placement);
// If a place for the rectangle could be found, update the height slice table to
// mark the region of the rectangle as being taken.
if(fits)
integrateRectangle(placement.X, rectangleWidth, placement.Y + rectangleHeight);
return fits;
}
/// <summary>Finds the best position for a rectangle of the given dimensions</summary>
/// <param name="rectangleWidth">Width of the rectangle to find a position for</param>
/// <param name="rectangleHeight">Height of the rectangle to find a position for</param>
/// <param name="placement">Receives the best placement found for the rectangle</param>
/// <returns>True if a valid placement for the rectangle could be found</returns>
private bool tryFindBestPlacement(
int rectangleWidth, int rectangleHeight, out Point placement
) {
// Slice index, vertical position and score of the best placement we could find
int bestSliceIndex = -1; // Slice index where the best placement was found
int bestSliceY = 0; // Y position of the best placement found
int bestScore = PackingAreaWidth * PackingAreaHeight; // lower == better!
// This is the counter for the currently checked position. The search works by
// skipping from slice to slice, determining the suitability of the location for the
// placement of the rectangle.
int leftSliceIndex = 0;
// Determine the slice in which the right end of the rectangle is located
int rightSliceIndex = this.heightSlices.BinarySearch(
new Point(rectangleWidth, 0), SliceStartComparer.Default
);
if(rightSliceIndex < 0)
rightSliceIndex = ~rightSliceIndex;
while(rightSliceIndex <= this.heightSlices.Count) {
// Determine the highest slice within the slices covered by the rectangle at
// its current placement. We cannot put the rectangle any lower than this without
// overlapping the other rectangles.
int highest = this.heightSlices[leftSliceIndex].Y;
for(int index = leftSliceIndex + 1; index < rightSliceIndex; ++index)
if(this.heightSlices[index].Y > highest)
highest = this.heightSlices[index].Y;
// Only process this position if it doesn't leave the packing area
if((highest + rectangleHeight < PackingAreaHeight)) {
int score = highest;
if(score < bestScore) {
bestSliceIndex = leftSliceIndex;
bestSliceY = highest;
bestScore = score;
}
}
// Advance the starting slice to the next slice start
++leftSliceIndex;
if(leftSliceIndex >= this.heightSlices.Count)
break;
// Advance the ending slice until we're on the proper slice again, given the new
// starting position of the rectangle.
int rightRectangleEnd = this.heightSlices[leftSliceIndex].X + rectangleWidth;
for(; rightSliceIndex <= this.heightSlices.Count; ++rightSliceIndex) {
int rightSliceStart;
if(rightSliceIndex == this.heightSlices.Count)
rightSliceStart = PackingAreaWidth;
else
rightSliceStart = this.heightSlices[rightSliceIndex].X;
// Is this the slice we're looking for?
if(rightSliceStart > rightRectangleEnd)
break;
}
// If we crossed the end of the slice array, the rectangle's right end has left
// the packing area, and thus, our search ends.
if(rightSliceIndex > this.heightSlices.Count)
break;
} // while rightSliceIndex <= this.heightSlices.Count
// Return the best placement we found for this rectangle. If the rectangle
// didn't fit anywhere, the slice index will still have its initialization value
// of -1 and we can report that no placement could be found.
if(bestSliceIndex == -1) {
placement = Point.Zero;
return false;
} else {
placement = new Point(this.heightSlices[bestSliceIndex].X, bestSliceY);
return true;
}
}
/// <summary>Integrates a new rectangle into the height slice table</summary>
/// <param name="left">Position of the rectangle's left side</param>
/// <param name="width">Width of the rectangle</param>
/// <param name="bottom">Position of the rectangle's lower side</param>
private void integrateRectangle(int left, int width, int bottom) {
// Find the first slice that is touched by the rectangle
int startSlice = this.heightSlices.BinarySearch(
new Point(left, 0), SliceStartComparer.Default
);
int firstSliceOriginalHeight;
// Did we score a direct hit on an existing slice start?
if(startSlice >= 0) {
// We scored a direct hit, so we can replace the slice we have hit
firstSliceOriginalHeight = this.heightSlices[startSlice].Y;
this.heightSlices[startSlice] = new Point(left, bottom);
} else { // No direct hit, slice starts inside another slice
// Add a new slice after the slice in which we start
startSlice = ~startSlice;
firstSliceOriginalHeight = this.heightSlices[startSlice - 1].Y;
this.heightSlices.Insert(startSlice, new Point(left, bottom));
}
int right = left + width;
++startSlice;
// Special case, the rectangle started on the last slice, so we cannot
// use the start slice + 1 for the binary search and the possibly already
// modified start slice height now only remains in our temporary
// firstSliceOriginalHeight variable
if(startSlice >= this.heightSlices.Count) {
// If the slice ends within the last slice (usual case, unless it has the
// exact same width the packing area has), add another slice to return to
// the original height at the end of the rectangle.
if(right < PackingAreaWidth)
this.heightSlices.Add(new Point(right, firstSliceOriginalHeight));
} else { // The rectangle doesn't start on the last slice
int endSlice = this.heightSlices.BinarySearch(
startSlice, this.heightSlices.Count - startSlice,
new Point(right, 0), SliceStartComparer.Default
);
// Another direct hit on the final slice's end?
if(endSlice > 0) {
this.heightSlices.RemoveRange(startSlice, endSlice - startSlice);
} else { // No direct hit, rectangle ends inside another slice
// Make index from negative BinarySearch() result
endSlice = ~endSlice;
// Find out to which height we need to return at the right end of
// the rectangle
int returnHeight;
if(endSlice == startSlice)
returnHeight = firstSliceOriginalHeight;
else
returnHeight = this.heightSlices[endSlice - 1].Y;
// Remove all slices covered by the rectangle and begin a new slice at its end
// to return back to the height of the slice on which the rectangle ends.
this.heightSlices.RemoveRange(startSlice, endSlice - startSlice);
if(right < PackingAreaWidth)
this.heightSlices.Insert(startSlice, new Point(right, returnHeight));
} // if endSlice > 0
} // if startSlice >= this.heightSlices.Count
}
/// <summary>Stores the height silhouette of the rectangles</summary>
private List<Point> heightSlices;
}
} // namespace Nuclex.Support.Packing