101 lines
3.3 KiB
C++
101 lines
3.3 KiB
C++
#ifndef LLMR_GEOMETRY_BINPACK
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#define LLMR_GEOMETRY_BINPACK
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#include <llmr/util/noncopyable.hpp>
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#include <llmr/util/rect.hpp>
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#include <cstdint>
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#include <list>
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namespace llmr {
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template <typename T>
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class BinPack : private util::noncopyable {
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public:
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BinPack(T width, T height)
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: free(1, Rect<uint16_t>{ 0, 0, width, height }) {}
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public:
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Rect<T> allocate(T width, T height) {
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// Find the smallest free rect angle
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auto smallest = free.end();
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for (auto it = free.begin(); it != free.end(); ++it) {
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const Rect<T>& ref = *it;
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const Rect<T>& rect = *smallest;
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if (width <= ref.w && height <= ref.h) {
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if (smallest == free.end() || (ref.y <= rect.y && ref.x <= rect.x)) {
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smallest = it;
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}
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}
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}
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if (smallest == free.end()) {
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// There's no space left for this char.
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return Rect<uint16_t>{ 0, 0, 0, 0 };
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} else {
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Rect<T> rect = *smallest;
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free.erase(smallest);
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// Shorter/Longer Axis Split Rule (SAS)
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// http://clb.demon.fi/files/RectangleBinPack.pdf p. 15
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// Ignore the dimension of R and just split long the shorter dimension
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// See Also: http://www.cs.princeton.edu/~chazelle/pubs/blbinpacking.pdf
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if (rect.w < rect.h) {
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// split horizontally
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// +--+---+
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// |__|___| <-- b1
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// +------+ <-- b2
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if (rect.w > width) free.emplace_back(rect.x + width, rect.y, rect.w - width, height);
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if (rect.h > height) free.emplace_back(rect.x, rect.y + height, rect.w, rect.h - height);
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} else {
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// split vertically
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// +--+---+
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// |__| | <-- b1
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// +--|---+ <-- b2
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if (rect.w > width) free.emplace_back(rect.x + width, rect.y, rect.w - width, rect.h);
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if (rect.h > height) free.emplace_back(rect.x, rect.y + height, width, rect.h - height);
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}
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return Rect<uint16_t>{ rect.x, rect.y, width, height };
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}
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}
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void release(Rect<T> rect) {
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// Simple algorithm to recursively merge the newly released cell with its
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// neighbor. This doesn't merge more than two cells at a time, and fails
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// for complicated merges.
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for (auto it = free.begin(); it != free.end(); ++it) {
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Rect<T> ref = *it;
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if (ref.y == rect.y && ref.h == rect.h && ref.x + ref.w == rect.x) {
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ref.w += rect.w;
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}
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else if (ref.x == rect.x && ref.w == rect.w && ref.y + ref.h == rect.y) {
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ref.h += rect.h;
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}
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else if (rect.y == ref.y && rect.h == ref.h && rect.x + rect.w == ref.x) {
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ref.x = rect.x;
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ref.w += rect.w;
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}
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else if (rect.x == ref.x && rect.w == ref.w && rect.y + rect.h == ref.y) {
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ref.y = rect.y;
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ref.h += rect.h;
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} else {
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continue;
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}
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free.erase(it);
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release(ref);
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return;
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}
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free.emplace_back(rect);
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};
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private:
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std::list<Rect<T>> free;
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};
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}
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#endif
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