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561 lines
16 KiB
C
561 lines
16 KiB
C
/*
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* stb_rect_pack.h - v0.06 - public domain - rectangle packing
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* Sean Barrett 2014
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*
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* Useful for e.g. packing rectangular textures into an atlas.
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* Does not do rotation.
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*
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* Not necessarily the awesomest packing method, but better than
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* the totally naive one in stb_truetype (which is primarily what
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* this is meant to replace).
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*
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* Has only had a few tests run, may have issues.
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*
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* More docs to come.
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*
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* No memory allocations; uses qsort() and assert() from stdlib.
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* Can override those by defining STBRP_SORT and STBRP_ASSERT.
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*
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* This library currently uses the Skyline Bottom-Left algorithm.
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*
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* Please note: better rectangle packers are welcome! Please
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* implement them to the same API, but with a different init
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* function.
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*
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* Credits
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*
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* Library
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* Sean Barrett
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* Minor features
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* Martins Mozeiko
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* Bugfixes / warning fixes
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* [your name could be here]
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*
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* Version history:
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*
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* 0.06 (2015-04-15) added STBRP_SORT to allow replacing qsort
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* 0.05: added STBRP_ASSERT to allow replacing assert
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* 0.04: fixed minor bug in STBRP_LARGE_RECTS support
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* 0.01: initial release
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*/
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#ifndef STB_INCLUDE_STB_RECT_PACK_H
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#define STB_INCLUDE_STB_RECT_PACK_H
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#define STB_RECT_PACK_VERSION 1
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#ifdef STBRP_STATIC
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#define STBRP_DEF static
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#else
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#define STBRP_DEF extern
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#endif
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef struct stbrp_context stbrp_context;
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typedef struct stbrp_node stbrp_node;
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typedef struct stbrp_rect stbrp_rect;
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#ifdef STBRP_LARGE_RECTS
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typedef int stbrp_coord;
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#else
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typedef unsigned short stbrp_coord;
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#endif
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STBRP_DEF void stbrp_pack_rects (stbrp_context *context,
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stbrp_rect *rects, int num_rects);
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/* Assign packed locations to rectangles. The rectangles are of type
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* 'stbrp_rect' defined below, stored in the array 'rects', and there
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* are 'num_rects' many of them.
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*
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* Rectangles which are successfully packed have the 'was_packed' flag
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* set to a non-zero value and 'x' and 'y' store the minimum location
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* on each axis (i.e. bottom-left in cartesian coordinates, top-left
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* if you imagine y increasing downwards). Rectangles which do not fit
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* have the 'was_packed' flag set to 0.
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*
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* You should not try to access the 'rects' array from another thread
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* while this function is running, as the function temporarily reorders
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* the array while it executes.
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*
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* To pack into another rectangle, you need to call stbrp_init_target
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* again. To continue packing into the same rectangle, you can call
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* this function again. Calling this multiple times with multiple rect
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* arrays will probably produce worse packing results than calling it
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* a single time with the full rectangle array, but the option is
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* available.
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*/
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struct stbrp_rect
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{
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int id; /* reserved for your use: */
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stbrp_coord w, h; /* input: */
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stbrp_coord x, y; /* output: */
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int was_packed; /* non-zero if valid packing */
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}; /* 16 bytes, nominally */
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STBRP_DEF void stbrp_init_target (stbrp_context *context,
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int width, int height, stbrp_node *nodes, int num_nodes);
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/* Initialize a rectangle packer to:
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* pack a rectangle that is 'width' by 'height' in dimensions
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* using temporary storage provided by the array 'nodes', which is 'num_nodes' long
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*
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* You must call this function every time you start packing into a new target.
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*
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* There is no "shutdown" function. The 'nodes' memory must stay valid for
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* the following stbrp_pack_rects() call (or calls), but can be freed after
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* the call (or calls) finish.
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*
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* Note: to guarantee best results, either:
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* 1. make sure 'num_nodes' >= 'width'
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* or 2. call stbrp_allow_out_of_mem() defined below with 'allow_out_of_mem = 1'
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*
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* If you don't do either of the above things, widths will be quantized to multiples
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* of small integers to guarantee the algorithm doesn't run out of temporary storage.
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*
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* If you do #2, then the non-quantized algorithm will be used, but the algorithm
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* may run out of temporary storage and be unable to pack some rectangles.
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*/
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STBRP_DEF void stbrp_setup_allow_out_of_mem (stbrp_context *context, int allow_out_of_mem);
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/* Optionally call this function after init but before doing any packing to
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* change the handling of the out-of-temp-memory scenario, described above.
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* If you call init again, this will be reset to the default (false).
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*/
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STBRP_DEF void stbrp_setup_heuristic (stbrp_context *context, int heuristic);
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/* Optionally select which packing heuristic the library should use. Different
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* heuristics will produce better/worse results for different data sets.
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* If you call init again, this will be reset to the default.
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*/
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enum
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{
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STBRP_HEURISTIC_Skyline_default=0,
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STBRP_HEURISTIC_Skyline_BL_sortHeight = STBRP_HEURISTIC_Skyline_default,
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STBRP_HEURISTIC_Skyline_BF_sortHeight
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};
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/* the details of the following structures don't matter to you, but they must
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* be visible so you can handle the memory allocations for them
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*/
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struct stbrp_node
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{
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stbrp_coord x,y;
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stbrp_node *next;
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};
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struct stbrp_context
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{
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int width;
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int height;
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int align;
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int init_mode;
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int heuristic;
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int num_nodes;
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stbrp_node *active_head;
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stbrp_node *free_head;
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stbrp_node extra[2]; /* we allocate two extra nodes so optimal user-node-count is 'width' not 'width+2' */
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};
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#ifdef __cplusplus
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}
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#endif
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#endif
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/* IMPLEMENTATION SECTION */
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#ifdef STB_RECT_PACK_IMPLEMENTATION
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#ifndef STBRP_SORT
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#include <stdlib.h>
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#define STBRP_SORT qsort
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#endif
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#ifndef STBRP_ASSERT
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#include <assert.h>
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#define STBRP_ASSERT assert
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#endif
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enum
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{
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STBRP__INIT_skyline = 1
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};
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STBRP_DEF void stbrp_setup_heuristic(stbrp_context *context, int heuristic)
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{
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switch (context->init_mode)
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{
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case STBRP__INIT_skyline:
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STBRP_ASSERT(heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight || heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight);
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context->heuristic = heuristic;
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break;
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default:
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STBRP_ASSERT(0);
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}
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}
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STBRP_DEF void stbrp_setup_allow_out_of_mem(stbrp_context *context, int allow_out_of_mem)
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{
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/* if it's ok to run out of memory, then don't bother aligning them;
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* this gives better packing, but may fail due to OOM (even though
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* the rectangles easily fit). @TODO a smarter approach would be to only
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* quantize once we've hit OOM, then we could get rid of this parameter.
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*/
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if (allow_out_of_mem)
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context->align = 1;
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else
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{
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/* if it's not ok to run out of memory, then quantize the widths
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* so that num_nodes is always enough nodes.
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*
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* I.e. num_nodes * align >= width
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* align >= width / num_nodes
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* align = ceil(width/num_nodes)
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*/
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context->align = (context->width + context->num_nodes-1) / context->num_nodes;
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}
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}
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STBRP_DEF void stbrp_init_target(stbrp_context *context, int width, int height, stbrp_node *nodes, int num_nodes)
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{
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int i;
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#ifndef STBRP_LARGE_RECTS
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STBRP_ASSERT(width <= 0xffff && height <= 0xffff);
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#endif
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for (i=0; i < num_nodes-1; ++i)
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nodes[i].next = &nodes[i+1];
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nodes[i].next = NULL;
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context->init_mode = STBRP__INIT_skyline;
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context->heuristic = STBRP_HEURISTIC_Skyline_default;
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context->free_head = &nodes[0];
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context->active_head = &context->extra[0];
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context->width = width;
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context->height = height;
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context->num_nodes = num_nodes;
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stbrp_setup_allow_out_of_mem(context, 0);
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/* node 0 is the full width,
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* node 1 is the sentinel (lets us not store width explicitly) */
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context->extra[0].x = 0;
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context->extra[0].y = 0;
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context->extra[0].next = &context->extra[1];
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context->extra[1].x = (stbrp_coord) width;
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#ifdef STBRP_LARGE_RECTS
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context->extra[1].y = (1<<30);
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#else
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context->extra[1].y = 65535;
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#endif
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context->extra[1].next = NULL;
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}
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/* Find minimum y position if it starts at x1 */
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static int stbrp__skyline_find_min_y(stbrp_context *c,
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stbrp_node *first, int x0, int width, int *pwaste)
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{
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int min_y, visited_width, waste_area;
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stbrp_node *node = first;
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int x1 = x0 + width;
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STBRP_ASSERT(first->x <= x0);
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STBRP_ASSERT(node->next->x > x0);
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STBRP_ASSERT(node->x <= x0);
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min_y = 0;
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waste_area = 0;
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visited_width = 0;
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while (node->x < x1)
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{
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if (node->y > min_y)
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{
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/* raise min_y higher.
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* we've accounted for all waste up to min_y,
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* but we'll now add more waste for everything we've visted
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*/
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waste_area += visited_width * (node->y - min_y);
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min_y = node->y;
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/* the first time through, visited_width might be reduced */
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if (node->x < x0)
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visited_width += node->next->x - x0;
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else
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visited_width += node->next->x - node->x;
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}
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else
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{
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/* add waste area */
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int under_width = node->next->x - node->x;
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if (under_width + visited_width > width)
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under_width = width - visited_width;
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waste_area += under_width * (min_y - node->y);
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visited_width += under_width;
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}
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node = node->next;
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}
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*pwaste = waste_area;
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return min_y;
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}
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typedef struct
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{
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int x,y;
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stbrp_node **prev_link;
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} stbrp__findresult;
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static stbrp__findresult stbrp__skyline_find_best_pos(stbrp_context *c, int width, int height)
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{
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int best_waste = (1<<30), best_x, best_y = (1 << 30);
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stbrp__findresult fr;
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stbrp_node **prev, *node, *tail, **best = NULL;
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/* align to multiple of c->align */
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width = (width + c->align - 1);
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width -= width % c->align;
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STBRP_ASSERT(width % c->align == 0);
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node = c->active_head;
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prev = &c->active_head;
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while (node->x + width <= c->width)
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{
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int waste;
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int y = stbrp__skyline_find_min_y(c, node, node->x, width, &waste);
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if (c->heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight)
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{
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/* actually just want to test BL bottom left */
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if (y < best_y)
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{
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best_y = y;
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best = prev;
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}
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}
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else
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{
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/* best-fit */
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if (y + height <= c->height)
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{
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/* can only use it if it first vertically */
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if (y < best_y || (y == best_y && waste < best_waste))
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{
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best_y = y;
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best_waste = waste;
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best = prev;
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}
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}
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}
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prev = &node->next;
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node = node->next;
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}
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best_x = (best == NULL) ? 0 : (*best)->x;
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/* if doing best-fit (BF), we also have to try aligning right edge to each node position
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*
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* e.g, if fitting
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*
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* ____________________
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* |____________________|
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*
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* into
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*
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* | |
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* | ____________|
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* |____________|
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*
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* then right-aligned reduces waste, but bottom-left BL is always chooses left-aligned
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*
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* This makes BF take about 2x the time
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*/
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if (c->heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight)
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{
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tail = c->active_head;
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node = c->active_head;
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prev = &c->active_head;
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/* find first node that's admissible */
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while (tail->x < width)
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tail = tail->next;
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while (tail)
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{
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int xpos = tail->x - width;
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int y,waste;
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STBRP_ASSERT(xpos >= 0);
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/* find the left position that matches this */
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while (node->next->x <= xpos)
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{
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prev = &node->next;
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node = node->next;
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}
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STBRP_ASSERT(node->next->x > xpos && node->x <= xpos);
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y = stbrp__skyline_find_min_y(c, node, xpos, width, &waste);
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if (y + height < c->height)
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{
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if (y <= best_y)
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{
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if (y < best_y || waste < best_waste || (waste==best_waste && xpos < best_x))
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{
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best_x = xpos;
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STBRP_ASSERT(y <= best_y);
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best_y = y;
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best_waste = waste;
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best = prev;
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}
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}
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}
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tail = tail->next;
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}
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}
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fr.prev_link = best;
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fr.x = best_x;
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fr.y = best_y;
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return fr;
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}
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static stbrp__findresult stbrp__skyline_pack_rectangle(stbrp_context *context, int width, int height)
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{
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/* find best position according to heuristic */
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stbrp_node *node, *cur;
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stbrp__findresult res = stbrp__skyline_find_best_pos(context, width, height);
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/* bail if:
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* 1. it failed
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* 2. the best node doesn't fit (we don't always check this)
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* 3. we're out of memory
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*/
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if (res.prev_link == NULL || res.y + height > context->height || context->free_head == NULL)
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{
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res.prev_link = NULL;
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return res;
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}
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/* on success, create new node */
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node = context->free_head;
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node->x = (stbrp_coord) res.x;
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node->y = (stbrp_coord) (res.y + height);
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context->free_head = node->next;
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/* insert the new node into the right starting point, and
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* let 'cur' point to the remaining nodes needing to be
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* stiched back in
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*/
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cur = *res.prev_link;
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if (cur->x < res.x)
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{
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/* preserve the existing one, so start testing with the next one */
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stbrp_node *next = cur->next;
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cur->next = node;
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cur = next;
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}
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else
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*res.prev_link = node;
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/* from here, traverse cur and free the nodes, until we get to one
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* that shouldn't be freed */
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while (cur->next && cur->next->x <= res.x + width)
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{
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stbrp_node *next = cur->next;
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/* move the current node to the free list */
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cur->next = context->free_head;
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context->free_head = cur;
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cur = next;
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}
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/* stitch the list back in */
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node->next = cur;
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if (cur->x < res.x + width)
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cur->x = (stbrp_coord) (res.x + width);
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return res;
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}
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static int rect_height_compare(const void *a, const void *b)
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{
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stbrp_rect *p = (stbrp_rect *) a;
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stbrp_rect *q = (stbrp_rect *) b;
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if (p->h > q->h)
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return -1;
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if (p->h < q->h)
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return 1;
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return (p->w > q->w) ? -1 : (p->w < q->w);
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}
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static int rect_width_compare(const void *a, const void *b)
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{
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stbrp_rect *p = (stbrp_rect *) a;
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stbrp_rect *q = (stbrp_rect *) b;
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if (p->w > q->w)
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return -1;
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if (p->w < q->w)
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return 1;
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return (p->h > q->h) ? -1 : (p->h < q->h);
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}
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static int rect_original_order(const void *a, const void *b)
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{
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stbrp_rect *p = (stbrp_rect *) a;
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stbrp_rect *q = (stbrp_rect *) b;
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return (p->was_packed < q->was_packed) ? -1 : (p->was_packed > q->was_packed);
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}
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#ifdef STBRP_LARGE_RECTS
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#define STBRP__MAXVAL 0xffffffff
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#else
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#define STBRP__MAXVAL 0xffff
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#endif
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STBRP_DEF void stbrp_pack_rects(stbrp_context *context, stbrp_rect *rects, int num_rects)
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{
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int i;
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/* we use the 'was_packed' field internally to allow sorting/unsorting */
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for (i=0; i < num_rects; ++i)
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{
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rects[i].was_packed = i;
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#ifndef STBRP_LARGE_RECTS
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STBRP_ASSERT(rects[i].w <= 0xffff && rects[i].h <= 0xffff);
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#endif
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}
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/* sort according to heuristic */
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STBRP_SORT(rects, num_rects, sizeof(rects[0]), rect_height_compare);
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for (i=0; i < num_rects; ++i)
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{
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stbrp__findresult fr = stbrp__skyline_pack_rectangle(context, rects[i].w, rects[i].h);
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if (fr.prev_link)
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{
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rects[i].x = (stbrp_coord) fr.x;
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rects[i].y = (stbrp_coord) fr.y;
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} else {
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rects[i].x = rects[i].y = STBRP__MAXVAL;
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}
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}
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/* unsort */
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STBRP_SORT(rects, num_rects, sizeof(rects[0]), rect_original_order);
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/* set was_packed flags */
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for (i=0; i < num_rects; ++i)
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rects[i].was_packed = !(rects[i].x == STBRP__MAXVAL && rects[i].y == STBRP__MAXVAL);
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}
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#endif
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