C++ port of shelf-pack
A 2D rectangular bin packing data structure that uses the Shelf Best Height Fit heuristic.
shelf-pack is a library for packing little rectangles into a big rectangle. This sounds simple enough,
but finding an optimal packing is a problem with NP-Complete
complexity. One useful application of bin packing is to assemble icons or glyphs into a sprite texture.
There are many ways to approach the bin packing problem, but shelf-pack uses the Shelf Best
Height Fit heuristic. It works by dividing the total space into "shelves", each with a certain height.
The allocator packs rectangles onto whichever shelf minimizes the amount of wasted vertical space.
shelf-pack is simple, fast, and works best when the rectangles have similar heights (icons and glyphs
are like this). It is not a generalized bin packer, and can potentially waste a lot of space if the
rectangles vary significantly in height.
#include <mapbox/shelf-pack.hpp>
#include <iostream>
using namespace mapbox;
void main(void) {
// Initialize the sprite with a width and height..
ShelfPack sprite(64, 64);
// Pack bins one at a time..
for (int i = 0; i < 5; i++) {
Bin* bin = sprite.packOne(-1, 10, 10);
// `packOne()` accepts parameters: `id`, `width`, `height`
// and returns a pointer to a single allocated Bin object..
// `id` is optional - pass `-1` and shelf-pack will make up a number for you..
if (bin) {
std::cout << *bin << std::endl;
} else {
std::cout << "out of space" << std::endl;
}
/* output:
Bin { id: 1, x: 0, y: 0, w: 10, h: 10, maxw: 10, maxh: 10, refcount: 1 }
Bin { id: 2, x: 32, y: 0, w: 10, h: 10, maxw: 10, maxh: 10, refcount: 1 }
Bin { id: 3, x: 0, y: 32, w: 10, h: 10, maxw: 10, maxh: 10, refcount: 1 }
Bin { id: 4, x: 32, y: 32, w: 10, h: 10, maxw: 10, maxh: 10, refcount: 1 }
out of space
*/
}
// Clear sprite and start over..
sprite.clear();
// Or, resize sprite by passing larger dimensions..
sprite.resize(128, 128); // width, height
}#include <mapbox/shelf-pack.hpp>
#include <iostream>
void main(void) {
// If you don't want to think about the size of the sprite,
// the `autoResize` option will allow it to grow as needed..
ShelfPack::ShelfPackOptions options;
options.autoResize = true;
ShelfPack sprite(10, 10, options);
// Bins can be allocated in batches..
// Each bin should be initialized with `id`, `w` (width), `h` (height)..
std::vector<Bin> bins;
bins.emplace_back(-1, 10, 10);
bins.emplace_back(-1, 10, 12);
bins.emplace_back(-1, 10, 12);
bins.emplace_back(-1, 10, 10);
// `pack()` returns a vector of Bin* pointers, with `x`, `y`, `w`, `h` values..
std::vector<Bin*> results = sprite.pack(bins);
for (const auto& bin : results) {
std::cout << *bin << std::endl;
}
/* output:
Bin { id: 1, x: 0, y: 0, w: 10, h: 10, maxw: 10, maxh: 10, refcount: 1 }
Bin { id: 2, x: 0, y: 10, w: 10, h: 12, maxw: 10, maxh: 12, refcount: 1 }
Bin { id: 3, x: 10, y: 10, w: 10, h: 12, maxw: 10, maxh: 12, refcount: 1 }
Bin { id: 4, x: 10, y: 0, w: 10, h: 10, maxw: 10, maxh: 10, refcount: 1 }
*/
// If you don't mind letting ShelfPack modify your objects,
// the `inPlace` option will assign `id`, `x`, `y` values to the incoming Bins.
// Fancy!
std::vector<Bin> myBins;
myBins.emplace_back(-1, 12, 24);
myBins.emplace_back(-1, 12, 12);
myBins.emplace_back(-1, 10, 10);
ShelfPack::PackOptions options;
options.inPlace = true;
sprite.pack(myBins, options);
for (const auto& mybin : myBins) {
std::cout << mybin << std::endl;
}
/* output:
{ id: 5, x: 0, y: 22, w: 12, h: 24, maxw: 12, maxh: 24, refcount: 1 }
{ id: 6, x: 20, y: 10, w: 12, h: 12, maxw: 12, maxh: 12, refcount: 1 }
{ id: 7, x: 20, y: 0, w: 10, h: 10, maxw: 10, maxh: 10, refcount: 1 }
*/
}
#include <mapbox/shelf-pack.hpp>
#include <iostream>
#include <array>
void main(void) {
// Initialize the sprite with a width and height..
ShelfPack sprite(64, 64);
Bin* bin;
// Allocated bins are automatically reference counted.
// They start out having a refcount of 1.
std::array<int32_t, 3> ids = { 100, 101, 102 };
for(const auto& id : ids) {
bin = sprite.packOne(id, 16, 16);
std::cout << *bin << std::endl;
}
/* output:
Bin { id: 100, x: 0, y: 0, w: 16, h: 16, maxw: 16, maxh: 16, refcount: 1 }
Bin { id: 101, x: 16, y: 0, w: 16, h: 16, maxw: 16, maxh: 16, refcount: 1 }
Bin { id: 102, x: 32, y: 0, w: 16, h: 16, maxw: 16, maxh: 16, refcount: 1 }
*/
// If you try to pack the same id again, shelf-pack will not re-pack it.
// Instead, it will increment the reference count automatically..
Bin* bin102 = sprite.packOne(102, 16, 16);
std::cout << *bin102 << std::endl;
/* output:
Bin { id: 102, x: 32, y: 0, w: 16, h: 16, maxw: 16, maxh: 16, refcount: 2 }
*/
// You can also manually increment the reference count..
Bin* bin101 = sprite.getBin(101);
sprite.ref(*bin101);
std::cout << *bin101 << std::endl;
/* output:
Bin { id: 101, x: 16, y: 0, w: 16, h: 16, maxw: 16, maxh: 16, refcount: 2 }
*/
// ...and decrement it!
Bin* bin100 = sprite.getBin(100);
sprite.unref(*bin100);
std::cout << *bin100 << std::endl;
/* output:
Bin { id: 100, x: 0, y: 0, w: 16, h: 16, maxw: 16, maxh: 16, refcount: 0 }
*/
// Bins with a refcount of 0 are considered free space.
// Next time a bin is packed, shelf-back tries to reuse free space first.
// See how Bin 103 gets allocated at [0,0] - Bin 100's old spot!
Bin* bin103 = sprite.packOne(103, 16, 15);
std::cout << *bin103 << std::endl;
/* output:
Bin { id: 103, x: 0, y: 0, w: 16, h: 15, maxw: 16, maxh: 16, refcount: 1 }
*/
// Bin 103 may be smaller (16x15) but it knows 16x16 was its original size.
// If that space becomes free again, a 16x16 bin will still fit there.
sprite.unref(*bin103);
Bin* bin104 = sprite.packOne(104, 16, 16);
std::cout << *bin104 << std::endl;
/* output:
Bin { id: 104, x: 0, y: 0, w: 16, h: 16, maxw: 16, maxh: 16, refcount: 1 }
*/
Complete API documentation can be found on the JavaScript version of the project: http://mapbox.github.io/shelf-pack/docs/
J. Jylänky, "A Thousand Ways to Pack the Bin - A Practical Approach to Two-Dimensional Rectangle Bin Packing," http://clb.demon.fi/files/RectangleBinPack.pdf, 2010