void workerpool_destroy(workerpool_t *wp)
{
if (wp == NULL)
return;
// force all worker threads to exit.
if (wp->nthreads > 1) {
for (int i = 0; i < wp->nthreads; i++)
workerpool_add_task(wp, NULL, NULL);
pthread_mutex_lock(&wp->mutex);
pthread_cond_broadcast(&wp->startcond);
pthread_mutex_unlock(&wp->mutex);
for (int i = 0; i < wp->nthreads; i++)
pthread_join(wp->threads[i], NULL);
pthread_mutex_destroy(&wp->mutex);
pthread_cond_destroy(&wp->startcond);
pthread_cond_destroy(&wp->endcond);
free(wp->threads);
}
zarray_destroy(wp->tasks);
free(wp);
}
zarray_t *apriltag_quad_thresh(apriltag_detector_t *td, image_u8_t *im)
{
////////////////////////////////////////////////////////
// step 1. threshold the image, creating the edge image.
int w = im->width, h = im->height, s = im->stride;
image_u8_t *threshim = threshold(td, im);
assert(threshim->stride == s);
image_u8_t *edgeim = image_u8_create(w, h);
if (1) {
image_u8_t *sumim = image_u8_create(w, h);
// apply a horizontal sum kernel of width 3
for (int y = 0; y < h; y++) {
for (int x = 1; x+1 < w; x++) {
sumim->buf[y*s + x] =
threshim->buf[y*s + x - 1] +
threshim->buf[y*s + x + 0] +
threshim->buf[y*s + x + 1];
}
}
timeprofile_stamp(td->tp, "sumim");
// deglitch
if (td->qtp.deglitch) {
for (int y = 1; y+1 < h; y++) {
for (int x = 1; x+1 < w; x++) {
// edge: black pixel next to white pixel
if (threshim->buf[y*s + x] == 0 &&
sumim->buf[y*s + x - s] + sumim->buf[y*s + x] + sumim->buf[y*s + x + s] == 8) {
threshim->buf[y*s + x] = 1;
sumim->buf[y*s + x - 1]++;
sumim->buf[y*s + x + 0]++;
sumim->buf[y*s + x + 1]++;
}
if (threshim->buf[y*s + x] == 1 &&
sumim->buf[y*s + x - s] + sumim->buf[y*s + x] + sumim->buf[y*s + x + s] == 1) {
threshim->buf[y*s + x] = 0;
sumim->buf[y*s + x - 1]--;
sumim->buf[y*s + x + 0]--;
sumim->buf[y*s + x + 1]--;
}
}
}
timeprofile_stamp(td->tp, "deglitch");
}
// apply a vertical sum kernel of width 3; check if any
// over-threshold pixels are adjacent to an under-threshold
// pixel.
//
// There are two types of edges: white pixels neighboring a
// black pixel, and black pixels neighboring a white pixel. We
// label these separately. (Values 0xc0 and 0x3f are picked
// such that they add to 255 (see below) and so that they can be
// viewed as pixel intensities for visualization purposes.)
//
// symmetry of detection. We don't want to use JUST "black
// near white" (or JUST "white near black"), because that
// biases the detection towards one side of the edge. This
// measurably reduces detection performance.
//
// On large tags, we could treat "neighbor" pixels the same
// way. But on very small tags, there may be other edges very
// near the tag edge. Since each of these edges is effectively
// two pixels thick (the white pixel near the black pixel, and
// the black pixel near the white pixel), it becomes likely
// that these two nearby edges will actually touch.
//
// A partial solution to this problem is to define edges to be
// adjacent white-near-black and black-near-white pixels.
//
for (int y = 1; y+1 < h; y++) {
for (int x = 1; x+1 < w; x++) {
if (threshim->buf[y*s + x] == 0) {
// edge: black pixel next to white pixel
if (sumim->buf[y*s + x - s] + sumim->buf[y*s + x] + sumim->buf[y*s + x + s] > 0)
edgeim->buf[y*s + x] = 0xc0;
} else {
// edge: white pixel next to black pixel when both
// edge types are on, we get less bias towards one
// side of the edge.
if (sumim->buf[y*s + x - s] + sumim->buf[y*s + x] + sumim->buf[y*s + x + s] < 9)
edgeim->buf[y*s + x] = 0x3f;
}
}
}
if (td->debug) {
for (int y = 0; y < h; y++) {
for (int x = 0; x < w; x++) {
threshim->buf[y*s + x] *= 255;
}
}
image_u8_write_pnm(threshim, "debug_threshold.pnm");
image_u8_write_pnm(edgeim, "debug_edge.pnm");
// image_u8_destroy(edgeim2);
}
image_u8_destroy(threshim);
image_u8_destroy(sumim);
}
timeprofile_stamp(td->tp, "edges");
////////////////////////////////////////////////////////
// step 2. find connected components.
unionfind_t *uf = unionfind_create(w * h);
for (int y = 1; y < h - 1; y++) {
for (int x = 1; x < w -1; x++) {
uint8_t v = edgeim->buf[y*s + x];
if (v==0)
continue;
// (dx,dy) pairs for 8 connectivity:
// (REFERENCE) (1, 0)
// (-1, 1) (0, 1) (1, 1)
//
// i.e., the minimum value of dx should be:
// y=0: 1
// y=1: -1
for (int dy = 0; dy <= 1; dy++) {
for (int dx = 1-2*dy; dx <= 1; dx++) {
if (edgeim->buf[(y+dy)*s + (x+dx)] == v) {
unionfind_connect(uf, y*w + x, (y+dy)*w + x + dx);
}
}
}
}
}
timeprofile_stamp(td->tp, "unionfind");
zhash_t *clustermap = zhash_create(sizeof(uint64_t), sizeof(zarray_t*),
zhash_uint64_hash, zhash_uint64_equals);
for (int y = 1; y < h-1; y++) {
for (int x = 1; x < w-1; x++) {
uint8_t v0 = edgeim->buf[y*s + x];
if (v0 == 0)
continue;
uint64_t rep0 = unionfind_get_representative(uf, y*w + x);
// 8 connectivity. (4 neighbors to check).
// for (int dy = 0; dy <= 1; dy++) {
// for (int dx = 1-2*dy; dx <= 1; dx++) {
// 4 connectivity. (2 neighbors to check)
for (int n = 1; n <= 2; n++) {
int dy = n & 1;
int dx = (n & 2) >> 1;
uint8_t v1 = edgeim->buf[(y+dy)*s + x + dx];
if (v0 + v1 != 255)
continue;
uint64_t rep1 = unionfind_get_representative(uf, (y+dy)*w + x+dx);
uint64_t clusterid;
if (rep0 < rep1)
clusterid = (rep1 << 32) + rep0;
else
clusterid = (rep0 << 32) + rep1;
zarray_t *cluster = NULL;
if (!zhash_get(clustermap, &clusterid, &cluster)) {
cluster = zarray_create(sizeof(struct pt));
zhash_put(clustermap, &clusterid, &cluster, NULL, NULL);
}
// NB: We will add some points multiple times to a
// given cluster. I don't know an efficient way to
// avoid that here; we remove them later on when we
// sort points by pt_compare_theta.
if (1) {
struct pt p = { .x = x, .y = y};
zarray_add(cluster, &p);
}
if (1) {
struct pt p = { .x = x+dx, .y = y+dy};
zarray_add(cluster, &p);
}
}
}
}
// make segmentation image.
if (td->debug) {
image_u8_t *d = image_u8_create(w, h);
assert(d->stride == s);
uint8_t *colors = (uint8_t*) calloc(w*h, 1);
for (int y = 0; y < h; y++) {
for (int x = 0; x < w; x++) {
uint32_t v = unionfind_get_representative(uf, y*w+x);
uint32_t sz = unionfind_get_set_size(uf, y*w+x);
if (sz < td->qtp.min_cluster_pixels)
continue;
uint8_t color = colors[v];
if (color == 0) {
const int bias = 20;
color = bias + (random() % (255-bias));
colors[v] = color;
}
float mix = 0.7;
mix = 1.0;
d->buf[y*d->stride + x] = mix*color + (1-mix)*im->buf[y*im->stride + x];
}
}
free(colors);
image_u8_write_pnm(d, "debug_segmentation.pnm");
image_u8_destroy(d);
}
timeprofile_stamp(td->tp, "make clusters");
////////////////////////////////////////////////////////
// step 3. process each connected component.
zarray_t *clusters = zhash_values(clustermap);
zhash_destroy(clustermap);
zarray_t *quads = zarray_create(sizeof(struct quad));
int sz = zarray_size(clusters);
int chunksize = 1 + sz / (APRILTAG_TASKS_PER_THREAD_TARGET * td->nthreads);
struct quad_task tasks[sz / chunksize + 1];
int ntasks = 0;
for (int i = 0; i < sz; i += chunksize) {
tasks[ntasks].td = td;
tasks[ntasks].cidx0 = i;
tasks[ntasks].cidx1 = imin(sz, i + chunksize);
tasks[ntasks].h = h;
tasks[ntasks].w = w;
tasks[ntasks].quads = quads;
tasks[ntasks].clusters = clusters;
tasks[ntasks].im = im;
workerpool_add_task(td->wp, do_quad_task, &tasks[ntasks]);
ntasks++;
}
workerpool_run(td->wp);
timeprofile_stamp(td->tp, "fit quads to clusters");
if (td->debug) {
FILE *f = fopen("debug_lines.ps", "w");
fprintf(f, "%%!PS\n\n");
image_u8_t *im2 = image_u8_copy(im);
image_u8_darken(im2);
image_u8_darken(im2);
// assume letter, which is 612x792 points.
double scale = fmin(612.0/im->width, 792.0/im2->height);
fprintf(f, "%.15f %.15f scale\n", scale, scale);
fprintf(f, "0 %d translate\n", im2->height);
fprintf(f, "1 -1 scale\n");
postscript_image(f, im);
for (int i = 0; i < zarray_size(quads); i++) {
struct quad *q;
zarray_get_volatile(quads, i, &q);
float rgb[3];
int bias = 100;
for (int i = 0; i < 3; i++)
rgb[i] = bias + (random() % (255-bias));
fprintf(f, "%f %f %f setrgbcolor\n", rgb[0]/255.0f, rgb[1]/255.0f, rgb[2]/255.0f);
fprintf(f, "%.15f %.15f moveto %.15f %.15f lineto %.15f %.15f lineto %.15f %.15f lineto %.15f %.15f lineto stroke\n",
q->p[0][0], q->p[0][1],
q->p[1][0], q->p[1][1],
q->p[2][0], q->p[2][1],
q->p[3][0], q->p[3][1],
q->p[0][0], q->p[0][1]);
}
fclose(f);
}
// printf(" %d %d %d %d\n", indices[0], indices[1], indices[2], indices[3]);
/*
if (td->debug) {
for (int i = 0; i < 4; i++) {
int i0 = indices[i];
int i1 = indices[(i+1)&3];
if (i1 < i0)
i1 += zarray_size(cluster);
for (int j = i0; j <= i1; j++) {
struct pt *p;
zarray_get_volatile(cluster, j % zarray_size(cluster), &p);
edgeim->buf[p->y*edgeim->stride + p->x] = 30+64*i;
}
}
} */
unionfind_destroy(uf);
for (int i = 0; i < zarray_size(clusters); i++) {
zarray_t *cluster;
zarray_get(clusters, i, &cluster);
zarray_destroy(cluster);
}
zarray_destroy(clusters);
image_u8_destroy(edgeim);
return quads;
}
