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#include <fitz.h>
/*
* Global Edge List -- list of straight path segments for scan conversion
*
* Stepping along the edges is with bresenham's line algorithm.
*
* See Mike Abrash -- Graphics Programming Black Book (notably chapter 40)
*/
fz_error *
fz_newgel(fz_gel **gelp)
{
fz_gel *gel;
gel = *gelp = fz_malloc(sizeof(fz_gel));
if (!gel)
return fz_outofmem;
gel->edges = nil;
gel->cap = 512;
gel->len = 0;
gel->edges = fz_malloc(sizeof(fz_edge) * gel->cap);
if (!gel->edges) {
fz_free(gel);
return fz_outofmem;
}
gel->xmin = gel->ymin = INT_MAX;
gel->xmax = gel->ymax = INT_MIN;
gel->hs = 1;
gel->vs = 1;
return nil;
}
void
fz_resetgel(fz_gel *gel, int hs, int vs)
{
gel->xmin = gel->ymin = INT_MAX;
gel->xmax = gel->ymax = INT_MIN;
gel->hs = hs;
gel->vs = vs;
gel->len = 0;
}
void
fz_dropgel(fz_gel *gel)
{
fz_free(gel->edges);
fz_free(gel);
}
fz_error *
fz_insertgel(fz_gel *gel, float fx0, float fy0, float fx1, float fy1)
{
fz_edge *edge;
int dx, dy;
int winding;
int width;
int tmp;
fx0 *= gel->hs;
fy0 *= gel->vs;
fx1 *= gel->hs;
fy1 *= gel->vs;
/* TODO: should we round or truncate? */
int x0 = fx0 < 0 ? fx0 - 0.5 : fx0 + 0.5;
int y0 = fy0 < 0 ? fy0 - 0.5 : fy0 + 0.5;
int x1 = fx1 < 0 ? fx1 - 0.5 : fx1 + 0.5;
int y1 = fy1 < 0 ? fy1 - 0.5 : fy1 + 0.5;
if (y0 == y1)
return nil;
if (y0 > y1) {
winding = -1;
tmp = x0; x0 = x1; x1 = tmp;
tmp = y0; y0 = y1; y1 = tmp;
}
else
winding = 1;
if (x0 < gel->xmin) gel->xmin = x0;
if (x0 > gel->xmax) gel->xmax = x0;
if (x1 < gel->xmin) gel->xmin = x1;
if (x1 > gel->xmax) gel->xmax = x1;
if (y0 < gel->ymin) gel->ymin = y0;
if (y1 > gel->ymax) gel->ymax = y1;
if (gel->len + 1 == gel->cap) {
int newcap = gel->cap + 512;
fz_edge *newedges = fz_realloc(gel->edges, sizeof(fz_edge) * newcap);
if (!newedges)
return fz_outofmem;
gel->cap = newcap;
gel->edges = newedges;
}
edge = &gel->edges[gel->len++];
dy = y1 - y0;
dx = x1 - x0;
width = dx < 0 ? -dx : dx;
edge->xdir = dx > 0 ? 1 : -1;
edge->ydir = winding;
edge->x = x0;
edge->y = y0;
edge->h = dy;
edge->adjdown = dy;
/* initial error term going l->r and r->l */
if (dx >= 0)
edge->e = 0;
else
edge->e = -dy + 1;
/* y-major edge */
if (dy >= width) {
edge->xmove = 0;
edge->adjup = width;
}
/* x-major edge */
else {
edge->xmove = (width / dy) * edge->xdir;
edge->adjup = width % dy;
}
return nil;
}
void
fz_sortgel(fz_gel *gel)
{
fz_edge *a = gel->edges;
int n = gel->len;
int h, i, k;
fz_edge t;
h = 1;
if (n < 14) {
h = 1;
}
else {
while (h < n)
h = 3 * h + 1;
h /= 3;
h /= 3;
}
while (h > 0)
{
for (i = 0; i < n; i++) {
t = a[i];
k = i - h;
/* TODO: sort on y major, x minor */
while (k >= 0 && a[k].y > t.y) {
a[k + h] = a[k];
k -= h;
}
a[k + h] = t;
}
h /= 3;
}
}
/*
* Active Edge List -- keep track of active edges while sweeping
*/
fz_error *
fz_newael(fz_ael **aelp)
{
fz_ael *ael;
ael = *aelp = fz_malloc(sizeof(fz_ael));
if (!ael)
return fz_outofmem;
ael->cap = 64;
ael->len = 0;
ael->edges = fz_malloc(sizeof(fz_edge*) * ael->cap);
if (!ael->edges) {
fz_free(ael);
return fz_outofmem;
}
return nil;
}
void
fz_dropael(fz_ael *ael)
{
fz_free(ael->edges);
fz_free(ael);
}
static inline void
sortael(fz_edge **a, int n)
{
int h, i, k;
fz_edge *t;
h = 1;
if (n < 14) {
h = 1;
}
else {
while (h < n)
h = 3 * h + 1;
h /= 3;
h /= 3;
}
while (h > 0)
{
for (i = 0; i < n; i++) {
t = a[i];
k = i - h;
while (k >= 0 && a[k]->x > t->x) {
a[k + h] = a[k];
k -= h;
}
a[k + h] = t;
}
h /= 3;
}
}
fz_error *
fz_insertael(fz_ael *ael, fz_gel *gel, int y, int *e)
{
/* insert edges that start here */
while (*e < gel->len && gel->edges[*e].y == y) {
if (ael->len + 1 == ael->cap) {
int newcap = ael->cap + 64;
fz_edge **newedges = fz_realloc(ael->edges, sizeof(fz_edge*) * newcap);
if (!newedges)
return fz_outofmem;
ael->edges = newedges;
ael->cap = newcap;
}
ael->edges[ael->len++] = &gel->edges[(*e)++];
}
/* shell-sort the edges by increasing x */
sortael(ael->edges, ael->len);
return nil;
}
void
fz_advanceael(fz_ael *ael)
{
fz_edge *edge;
int i = 0;
while (i < ael->len)
{
edge = ael->edges[i];
edge->h --;
/* terminator! */
if (edge->h == 0) {
ael->edges[i] = ael->edges[--ael->len];
}
else {
edge->x += edge->xmove;
edge->e += edge->adjup;
if (edge->e > 0) {
edge->x += edge->xdir;
edge->e -= edge->adjdown;
}
i ++;
}
}
}
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