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Nuklear/stb_rect_pack.h

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/* stb_rect_pack.h - v0.05 - public domain - rectangle packing */
/* Sean Barrett 2014 */
/* */
/* Useful for e.g. packing rectangular textures into an atlas. */
/* Does not do rotation. */
/* */
/* Not necessarily the awesomest packing method, but better than */
/* the totally naive one in stb_truetype (which is primarily what */
/* this is meant to replace). */
/* */
/* Has only had a few tests run, may have issues. */
/* */
/* More docs to come. */
/* */
/* No memory allocations; uses qsort() and assert() from stdlib. */
/* */
/* This library currently uses the Skyline Bottom-Left algorithm. */
/* */
/* Please note: better rectangle packers are welcome! Please */
/* implement them to the same API, but with a different init */
/* function. */
/* */
/* Version history: */
/* */
/* 0.05: added STBRP_ASSERT to allow replacing assert */
/* 0.04: fixed minor bug in STBRP_LARGE_RECTS support */
/* 0.01: initial release */
/*//////////////////////////////////////////////////////////////////////////// */
/* */
/* INCLUDE SECTION */
#ifndef STB_INCLUDE_STB_RECT_PACK_H
#define STB_INCLUDE_STB_RECT_PACK_H
#define STB_RECT_PACK_VERSION 1
#ifdef STBRP_STATIC
#define STBRP_DEF static
#else
#define STBRP_DEF extern
#endif
#ifdef __cplusplus
extern "C" {
#endif
typedef struct stbrp_context stbrp_context;
typedef struct stbrp_node stbrp_node;
typedef struct stbrp_rect stbrp_rect;
#ifdef STBRP_LARGE_RECTS
typedef int stbrp_coord;
#else
typedef unsigned short stbrp_coord;
#endif
STBRP_DEF void stbrp_pack_rects (stbrp_context *context, stbrp_rect *rects, int num_rects);
/* Assign packed locations to rectangles. The rectangles are of type */
/* 'stbrp_rect' defined below, stored in the array 'rects', and there */
/* are 'num_rects' many of them. */
/* */
/* Rectangles which are successfully packed have the 'was_packed' flag */
/* set to a non-zero value and 'x' and 'y' store the minimum location */
/* on each axis (i.e. bottom-left in cartesian coordinates, top-left */
/* if you imagine y increasing downwards). Rectangles which do not fit */
/* have the 'was_packed' flag set to 0. */
/* */
/* You should not try to access the 'rects' array from another thread */
/* while this function is running, as the function temporarily reorders */
/* the array while it executes. */
/* */
/* To pack into another rectangle, you need to call stbrp_init_target */
/* again. To continue packing into the same rectangle, you can call */
/* this function again. Calling this multiple times with multiple rect */
/* arrays will probably produce worse packing results than calling it */
/* a single time with the full rectangle array, but the option is */
/* available. */
struct stbrp_rect
{
/* reserved for your use: */
int id;
/* input: */
stbrp_coord w, h;
/* output: */
stbrp_coord x, y;
int was_packed; /* non-zero if valid packing */
}; /* 16 bytes, nominally */
STBRP_DEF void stbrp_init_target (stbrp_context *context, int width, int height, stbrp_node *nodes, int num_nodes);
/* Initialize a rectangle packer to: */
/* pack a rectangle that is 'width' by 'height' in dimensions */
/* using temporary storage provided by the array 'nodes', which is 'num_nodes' long */
/* */
/* You must call this function every time you start packing into a new target. */
/* */
/* There is no "shutdown" function. The 'nodes' memory must stay valid for */
/* the following stbrp_pack_rects() call (or calls), but can be freed after */
/* the call (or calls) finish. */
/* */
/* Note: to guarantee best results, either: */
/* 1. make sure 'num_nodes' >= 'width' */
/* or 2. call stbrp_allow_out_of_mem() defined below with 'allow_out_of_mem = 1' */
/* */
/* If you don't do either of the above things, widths will be quantized to multiples */
/* of small integers to guarantee the algorithm doesn't run out of temporary storage. */
/* */
/* If you do #2, then the non-quantized algorithm will be used, but the algorithm */
/* may run out of temporary storage and be unable to pack some rectangles. */
STBRP_DEF void stbrp_setup_allow_out_of_mem (stbrp_context *context, int allow_out_of_mem);
/* Optionally call this function after init but before doing any packing to */
/* change the handling of the out-of-temp-memory scenario, described above. */
/* If you call init again, this will be reset to the default (false). */
STBRP_DEF void stbrp_setup_heuristic (stbrp_context *context, int heuristic);
/* Optionally select which packing heuristic the library should use. Different */
/* heuristics will produce better/worse results for different data sets. */
/* If you call init again, this will be reset to the default. */
enum
{
STBRP_HEURISTIC_Skyline_default=0,
STBRP_HEURISTIC_Skyline_BL_sortHeight = STBRP_HEURISTIC_Skyline_default,
STBRP_HEURISTIC_Skyline_BF_sortHeight
};
/*//////////////////////////////////////////////////////////////////////////// */
/* */
/* the details of the following structures don't matter to you, but they must */
/* be visible so you can handle the memory allocations for them */
struct stbrp_node
{
stbrp_coord x,y;
stbrp_node *next;
};
struct stbrp_context
{
int width;
int height;
int align;
int init_mode;
int heuristic;
int num_nodes;
stbrp_node *active_head;
stbrp_node *free_head;
stbrp_node extra[2]; /* we allocate two extra nodes so optimal user-node-count is 'width' not 'width+2' */
};
#ifdef __cplusplus
}
#endif
#endif
/*//////////////////////////////////////////////////////////////////////////// */
/* */
/* IMPLEMENTATION SECTION */
/* */
#ifdef STB_RECT_PACK_IMPLEMENTATION
#include <stdlib.h>
#ifndef STBRP_ASSERT
#include <assert.h>
#define STBRP_ASSERT assert
#endif
enum
{
STBRP__INIT_skyline = 1
};
STBRP_DEF void stbrp_setup_heuristic(stbrp_context *context, int heuristic)
{
switch (context->init_mode) {
case STBRP__INIT_skyline:
STBRP_ASSERT(heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight || heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight);
context->heuristic = heuristic;
break;
default:
STBRP_ASSERT(0);
}
}
STBRP_DEF void stbrp_setup_allow_out_of_mem(stbrp_context *context, int allow_out_of_mem)
{
if (allow_out_of_mem)
/* if it's ok to run out of memory, then don't bother aligning them; */
/* this gives better packing, but may fail due to OOM (even though */
/* the rectangles easily fit). @TODO a smarter approach would be to only */
/* quantize once we've hit OOM, then we could get rid of this parameter. */
context->align = 1;
else {
/* if it's not ok to run out of memory, then quantize the widths */
/* so that num_nodes is always enough nodes. */
/* */
/* I.e. num_nodes * align >= width */
/* align >= width / num_nodes */
/* align = ceil(width/num_nodes) */
context->align = (context->width + context->num_nodes-1) / context->num_nodes;
}
}
STBRP_DEF void stbrp_init_target(stbrp_context *context, int width, int height, stbrp_node *nodes, int num_nodes)
{
int i;
#ifndef STBRP_LARGE_RECTS
STBRP_ASSERT(width <= 0xffff && height <= 0xffff);
#endif
for (i=0; i < num_nodes-1; ++i)
nodes[i].next = &nodes[i+1];
nodes[i].next = NULL;
context->init_mode = STBRP__INIT_skyline;
context->heuristic = STBRP_HEURISTIC_Skyline_default;
context->free_head = &nodes[0];
context->active_head = &context->extra[0];
context->width = width;
context->height = height;
context->num_nodes = num_nodes;
stbrp_setup_allow_out_of_mem(context, 0);
/* node 0 is the full width, node 1 is the sentinel (lets us not store width explicitly) */
context->extra[0].x = 0;
context->extra[0].y = 0;
context->extra[0].next = &context->extra[1];
context->extra[1].x = (stbrp_coord) width;
#ifdef STBRP_LARGE_RECTS
context->extra[1].y = (1<<30);
#else
context->extra[1].y = 65535;
#endif
context->extra[1].next = NULL;
}
/* find minimum y position if it starts at x1 */
static int stbrp__skyline_find_min_y(stbrp_context *c, stbrp_node *first, int x0, int width, int *pwaste)
{
stbrp_node *node = first;
int x1 = x0 + width;
int min_y, visited_width, waste_area;
STBRP_ASSERT(first->x <= x0);
(void)c;
#if 0
/* skip in case we're past the node */
while (node->next->x <= x0)
++node;
#else
STBRP_ASSERT(node->next->x > x0); /* we ended up handling this in the caller for efficiency */
#endif
STBRP_ASSERT(node->x <= x0);
min_y = 0;
waste_area = 0;
visited_width = 0;
while (node->x < x1) {
if (node->y > min_y) {
/* raise min_y higher. */
/* we've accounted for all waste up to min_y, */
/* but we'll now add more waste for everything we've visted */
waste_area += visited_width * (node->y - min_y);
min_y = node->y;
/* the first time through, visited_width might be reduced */
if (node->x < x0)
visited_width += node->next->x - x0;
else
visited_width += node->next->x - node->x;
} else {
/* add waste area */
int under_width = node->next->x - node->x;
if (under_width + visited_width > width)
under_width = width - visited_width;
waste_area += under_width * (min_y - node->y);
visited_width += under_width;
}
node = node->next;
}
*pwaste = waste_area;
return min_y;
}
typedef struct
{
int x,y;
stbrp_node **prev_link;
} stbrp__findresult;
static stbrp__findresult stbrp__skyline_find_best_pos(stbrp_context *c, int width, int height)
{
int best_waste = (1<<30), best_x, best_y = (1 << 30);
stbrp__findresult fr;
stbrp_node **prev, *node, *tail, **best = NULL;
/* align to multiple of c->align */
width = (width + c->align - 1);
width -= width % c->align;
STBRP_ASSERT(width % c->align == 0);
node = c->active_head;
prev = &c->active_head;
while (node->x + width <= c->width) {
int y,waste;
y = stbrp__skyline_find_min_y(c, node, node->x, width, &waste);
if (c->heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight) { /* actually just want to test BL */
/* bottom left */
if (y < best_y) {
best_y = y;
best = prev;
}
} else {
/* best-fit */
if (y + height <= c->height) {
/* can only use it if it first vertically */
if (y < best_y || (y == best_y && waste < best_waste)) {
best_y = y;
best_waste = waste;
best = prev;
}
}
}
prev = &node->next;
node = node->next;
}
best_x = (best == NULL) ? 0 : (*best)->x;
/* if doing best-fit (BF), we also have to try aligning right edge to each node position */
/* */
/* e.g, if fitting */
/* */
/* ____________________ */
/* |____________________| */
/* */
/* into */
/* */
/* | | */
/* | ____________| */
/* |____________| */
/* */
/* then right-aligned reduces waste, but bottom-left BL is always chooses left-aligned */
/* */
/* This makes BF take about 2x the time */
if (c->heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight) {
tail = c->active_head;
node = c->active_head;
prev = &c->active_head;
/* find first node that's admissible */
while (tail->x < width)
tail = tail->next;
while (tail) {
int xpos = tail->x - width;
int y,waste;
STBRP_ASSERT(xpos >= 0);
/* find the left position that matches this */
while (node->next->x <= xpos) {
prev = &node->next;
node = node->next;
}
STBRP_ASSERT(node->next->x > xpos && node->x <= xpos);
y = stbrp__skyline_find_min_y(c, node, xpos, width, &waste);
if (y + height < c->height) {
if (y <= best_y) {
if (y < best_y || waste < best_waste || (waste==best_waste && xpos < best_x)) {
best_x = xpos;
STBRP_ASSERT(y <= best_y);
best_y = y;
best_waste = waste;
best = prev;
}
}
}
tail = tail->next;
}
}
fr.prev_link = best;
fr.x = best_x;
fr.y = best_y;
return fr;
}
static stbrp__findresult stbrp__skyline_pack_rectangle(stbrp_context *context, int width, int height)
{
/* find best position according to heuristic */
stbrp__findresult res = stbrp__skyline_find_best_pos(context, width, height);
stbrp_node *node, *cur;
/* bail if: */
/* 1. it failed */
/* 2. the best node doesn't fit (we don't always check this) */
/* 3. we're out of memory */
if (res.prev_link == NULL || res.y + height > context->height || context->free_head == NULL) {
res.prev_link = NULL;
return res;
}
/* on success, create new node */
node = context->free_head;
node->x = (stbrp_coord) res.x;
node->y = (stbrp_coord) (res.y + height);
context->free_head = node->next;
/* insert the new node into the right starting point, and */
/* let 'cur' point to the remaining nodes needing to be */
/* stiched back in */
cur = *res.prev_link;
if (cur->x < res.x) {
/* preserve the existing one, so start testing with the next one */
stbrp_node *next = cur->next;
cur->next = node;
cur = next;
} else {
*res.prev_link = node;
}
/* from here, traverse cur and free the nodes, until we get to one */
/* that shouldn't be freed */
while (cur->next && cur->next->x <= res.x + width) {
stbrp_node *next = cur->next;
/* move the current node to the free list */
cur->next = context->free_head;
context->free_head = cur;
cur = next;
}
/* stitch the list back in */
node->next = cur;
if (cur->x < res.x + width)
cur->x = (stbrp_coord) (res.x + width);
#ifdef _DEBUG
cur = context->active_head;
while (cur->x < context->width) {
STBRP_ASSERT(cur->x < cur->next->x);
cur = cur->next;
}
STBRP_ASSERT(cur->next == NULL);
{
stbrp_node *L1 = NULL, *L2 = NULL;
int count=0;
cur = context->active_head;
while (cur) {
L1 = cur;
cur = cur->next;
++count;
}
cur = context->free_head;
while (cur) {
L2 = cur;
cur = cur->next;
++count;
}
STBRP_ASSERT(count == context->num_nodes+2);
}
#endif
return res;
}
static int rect_height_compare(const void *a, const void *b)
{
const stbrp_rect *p = (const stbrp_rect *) a;
const stbrp_rect *q = (const stbrp_rect *) b;
if (p->h > q->h)
return -1;
if (p->h < q->h)
return 1;
return (p->w > q->w) ? -1 : (p->w < q->w);
}
static int rect_width_compare(const void *a, const void *b)
{
const stbrp_rect *p = (const stbrp_rect *) a;
const stbrp_rect *q = (const stbrp_rect *) b;
if (p->w > q->w)
return -1;
if (p->w < q->w)
return 1;
return (p->h > q->h) ? -1 : (p->h < q->h);
}
static int rect_original_order(const void *a, const void *b)
{
const stbrp_rect *p = (const stbrp_rect *) a;
const stbrp_rect *q = (const stbrp_rect *) b;
return (p->was_packed < q->was_packed) ? -1 : (p->was_packed > q->was_packed);
}
#ifdef STBRP_LARGE_RECTS
#define STBRP__MAXVAL 0xffffffff
#else
#define STBRP__MAXVAL 0xffff
#endif
STBRP_DEF void stbrp_pack_rects(stbrp_context *context, stbrp_rect *rects, int num_rects)
{
int i;
/* we use the 'was_packed' field internally to allow sorting/unsorting */
for (i=0; i < num_rects; ++i) {
rects[i].was_packed = i;
#ifndef STBRP_LARGE_RECTS
STBRP_ASSERT(rects[i].w <= 0xffff && rects[i].h <= 0xffff);
#endif
}
/* sort according to heuristic */
qsort(rects, (size_t)num_rects, sizeof(rects[0]), rect_height_compare);
for (i=0; i < num_rects; ++i) {
stbrp__findresult fr = stbrp__skyline_pack_rectangle(context, rects[i].w, rects[i].h);
if (fr.prev_link) {
rects[i].x = (stbrp_coord) fr.x;
rects[i].y = (stbrp_coord) fr.y;
} else {
rects[i].x = rects[i].y = STBRP__MAXVAL;
}
}
/* unsort */
qsort(rects, (size_t)num_rects, sizeof(rects[0]), rect_original_order);
/* set was_packed flags */
for (i=0; i < num_rects; ++i)
rects[i].was_packed = !(rects[i].x == STBRP__MAXVAL && rects[i].y == STBRP__MAXVAL);
}
#endif
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