125 lines
3.9 KiB
JavaScript
125 lines
3.9 KiB
JavaScript
/**
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* potpack - by [@mourner](https://github.com/mourner)
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*
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* A tiny JavaScript function for packing 2D rectangles into a near-square container,
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* which is useful for generating CSS sprites and WebGL textures. Similar to
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* [shelf-pack](https://github.com/mapbox/shelf-pack), but static (you can't add items
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* once a layout is generated), and aims for maximal space utilization.
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*
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* A variation of algorithms used in [rectpack2D](https://github.com/TeamHypersomnia/rectpack2D)
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* and [bin-pack](https://github.com/bryanburgers/bin-pack), which are in turn based
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* on [this article by Blackpawn](http://blackpawn.com/texts/lightmaps/default.html).
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*
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* @license
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* ISC License
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*
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* Copyright (c) 2018, Mapbox
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*
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* Permission to use, copy, modify, and/or distribute this software for any purpose
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* with or without fee is hereby granted, provided that the above copyright notice
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* and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
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* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
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* FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
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* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
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* OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
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* TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
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* THIS SOFTWARE.
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*/
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function potpack(boxes) {
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// calculate total box area and maximum box width
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let area = 0;
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let maxWidth = 0;
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for (const box of boxes) {
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area += box.w * box.h;
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maxWidth = Math.max(maxWidth, box.w);
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}
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// sort the boxes for insertion by height, descending
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boxes.sort((a, b) => b.h - a.h);
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// aim for a squarish resulting container,
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// slightly adjusted for sub-100% space utilization
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const startWidth = Math.max(Math.ceil(Math.sqrt(area / 0.95)), maxWidth);
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// start with a single empty space, unbounded at the bottom
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const spaces = [{x: 0, y: 0, w: startWidth, h: Infinity}];
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let width = 0;
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let height = 0;
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for (const box of boxes) {
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// look through spaces backwards so that we check smaller spaces first
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for (let i = spaces.length - 1; i >= 0; i--) {
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const space = spaces[i];
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// look for empty spaces that can accommodate the current box
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if (box.w > space.w || box.h > space.h) continue;
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// found the space; add the box to its top-left corner
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// |-------|-------|
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// | box | |
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// |_______| |
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// | space |
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// |_______________|
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box.x = space.x;
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box.y = space.y;
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height = Math.max(height, box.y + box.h);
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width = Math.max(width, box.x + box.w);
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if (box.w === space.w && box.h === space.h) {
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// space matches the box exactly; remove it
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const last = spaces.pop();
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if (i < spaces.length) spaces[i] = last;
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} else if (box.h === space.h) {
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// space matches the box height; update it accordingly
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// |-------|---------------|
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// | box | updated space |
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// |_______|_______________|
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space.x += box.w;
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space.w -= box.w;
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} else if (box.w === space.w) {
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// space matches the box width; update it accordingly
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// |---------------|
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// | box |
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// |_______________|
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// | updated space |
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// |_______________|
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space.y += box.h;
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space.h -= box.h;
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} else {
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// otherwise the box splits the space into two spaces
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// |-------|-----------|
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// | box | new space |
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// |_______|___________|
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// | updated space |
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// |___________________|
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spaces.push({
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x: space.x + box.w,
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y: space.y,
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w: space.w - box.w,
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h: box.h
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});
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space.y += box.h;
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space.h -= box.h;
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}
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break;
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}
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}
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return {
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w: width, // container width
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h: height, // container height
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fill: (area / (width * height)) || 0 // space utilization
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};
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}
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export { potpack }; |