PostGIS 3.0.6dev-r@@SVN_REVISION@@
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◆ rt_band_get_nearest_pixel()

uint32_t rt_band_get_nearest_pixel ( rt_band  band,
int  x,
int  y,
uint16_t  distancex,
uint16_t  distancey,
int  exclude_nodata_value,
rt_pixel *  npixels 
)

Get nearest pixel(s) with value (not NODATA) to specified pixel.

Parameters
band: the band to get nearest pixel(s) from
x: the column of the pixel (0-based)
y: the line of the pixel (0-based)
distancex: the number of pixels around the specified pixel along the X axis
distancey: the number of pixels around the specified pixel along the Y axis
exclude_nodata_value: if non-zero, ignore nodata values to check for pixels with value
npixels: return set of rt_pixel object or NULL
Returns
-1 on error, otherwise the number of rt_pixel objects in npixels

Definition at line 1374 of file rt_band.c.

1380 {
1381 rt_pixel npixel = NULL;
1382 int extent[4] = {0};
1383 int max_extent[4] = {0};
1384 int d0 = 0;
1385 uint32_t distance[2] = {0};
1386 uint32_t _d[2] = {0};
1387 uint32_t i = 0;
1388 uint32_t j = 0;
1389 uint32_t k = 0;
1390 int _max = 0;
1391 int _x = 0;
1392 int _y = 0;
1393 int *_min = NULL;
1394 double pixval = 0;
1395 double minval = 0;
1396 uint32_t count = 0;
1397 int isnodata = 0;
1398
1399 int inextent = 0;
1400
1401 assert(NULL != band);
1402 assert(NULL != npixels);
1403
1404 RASTER_DEBUG(3, "Starting");
1405
1406 /* process distance */
1407 distance[0] = distancex;
1408 distance[1] = distancey;
1409
1410 /* no distance, means get nearest pixels and return */
1411 if (!distance[0] && !distance[1])
1412 d0 = 1;
1413
1414 RASTER_DEBUGF(4, "Selected pixel: %d x %d", x, y);
1415 RASTER_DEBUGF(4, "Distances: %d x %d", distance[0], distance[1]);
1416
1417 /* shortcuts if outside band extent */
1418 if (
1419 exclude_nodata_value && (
1420 (x < 0 || x > band->width) ||
1421 (y < 0 || y > band->height)
1422 )
1423 ) {
1424 /* no distances specified, jump to pixel close to extent */
1425 if (d0) {
1426 if (x < 0)
1427 x = -1;
1428 else if (x > band->width)
1429 x = band->width;
1430
1431 if (y < 0)
1432 y = -1;
1433 else if (y > band->height)
1434 y = band->height;
1435
1436 RASTER_DEBUGF(4, "Moved selected pixel: %d x %d", x, y);
1437 }
1438 /*
1439 distances specified
1440 if distances won't capture extent of band, return 0
1441 */
1442 else if (
1443 ((x < 0 && (uint32_t) abs(x) > distance[0]) || (x - band->width >= (int)distance[0])) ||
1444 ((y < 0 && (uint32_t) abs(y) > distance[1]) || (y - band->height >= (int)distance[1]))
1445 ) {
1446 RASTER_DEBUG(4, "No nearest pixels possible for provided pixel and distances");
1447 return 0;
1448 }
1449 }
1450
1451 /* no NODATA, exclude is FALSE */
1452 if (!band->hasnodata)
1453 exclude_nodata_value = FALSE;
1454 /* band is NODATA and excluding NODATA */
1455 else if (exclude_nodata_value && band->isnodata) {
1456 RASTER_DEBUG(4, "No nearest pixels possible as band is NODATA and excluding NODATA values");
1457 return 0;
1458 }
1459
1460 /* determine the maximum distance to prevent an infinite loop */
1461 if (d0) {
1462 int a, b;
1463
1464 /* X axis */
1465 a = abs(x);
1466 b = abs(x - band->width);
1467
1468 if (a > b)
1469 distance[0] = a;
1470 else
1471 distance[0] = b;
1472
1473 /* Y axis */
1474 a = abs(y);
1475 b = abs(y - band->height);
1476 if (a > b)
1477 distance[1] = a;
1478 else
1479 distance[1] = b;
1480
1481 RASTER_DEBUGF(4, "Maximum distances: %d x %d", distance[0], distance[1]);
1482 }
1483
1484 /* minimum possible value for pixel type */
1485 minval = rt_pixtype_get_min_value(band->pixtype);
1486 RASTER_DEBUGF(4, "pixtype: %s", rt_pixtype_name(band->pixtype));
1487 RASTER_DEBUGF(4, "minval: %f", minval);
1488
1489 /* set variables */
1490 count = 0;
1491 *npixels = NULL;
1492
1493 /* maximum extent */
1494 max_extent[0] = x - (int)distance[0]; /* min X */
1495 max_extent[1] = y - (int)distance[1]; /* min Y */
1496 max_extent[2] = x + (int)distance[0]; /* max X */
1497 max_extent[3] = y + (int)distance[1]; /* max Y */
1498 RASTER_DEBUGF(4, "Maximum Extent: (%d, %d, %d, %d)",
1499 max_extent[0], max_extent[1], max_extent[2], max_extent[3]);
1500
1501 _d[0] = 0;
1502 _d[1] = 0;
1503 do {
1504 _d[0]++;
1505 _d[1]++;
1506
1507 extent[0] = x - (int)_d[0]; /* min x */
1508 extent[1] = y - (int)_d[1]; /* min y */
1509 extent[2] = x + (int)_d[0]; /* max x */
1510 extent[3] = y + (int)_d[1]; /* max y */
1511
1512 RASTER_DEBUGF(4, "Processing distances: %d x %d", _d[0], _d[1]);
1513 RASTER_DEBUGF(4, "Extent: (%d, %d, %d, %d)",
1514 extent[0], extent[1], extent[2], extent[3]);
1515
1516 for (i = 0; i < 2; i++) {
1517
1518 /* by row */
1519 if (i < 1)
1520 _max = extent[2] - extent[0] + 1;
1521 /* by column */
1522 else
1523 _max = extent[3] - extent[1] + 1;
1524 _max = abs(_max);
1525
1526 for (j = 0; j < 2; j++) {
1527 /* by row */
1528 if (i < 1) {
1529 _x = extent[0];
1530 _min = &_x;
1531
1532 /* top row */
1533 if (j < 1)
1534 _y = extent[1];
1535 /* bottom row */
1536 else
1537 _y = extent[3];
1538 }
1539 /* by column */
1540 else {
1541 _y = extent[1] + 1;
1542 _min = &_y;
1543
1544 /* left column */
1545 if (j < 1) {
1546 _x = extent[0];
1547 _max -= 2;
1548 }
1549 /* right column */
1550 else
1551 _x = extent[2];
1552 }
1553
1554 RASTER_DEBUGF(4, "_min, _max: %d, %d", *_min, _max);
1555 for (k = 0; k < (uint32_t) _max; k++) {
1556 /* check that _x and _y are not outside max extent */
1557 if (
1558 _x < max_extent[0] || _x > max_extent[2] ||
1559 _y < max_extent[1] || _y > max_extent[3]
1560 ) {
1561 (*_min)++;
1562 continue;
1563 }
1564
1565 /* outside band extent, set to NODATA */
1566 if (
1567 (_x < 0 || _x >= band->width) ||
1568 (_y < 0 || _y >= band->height)
1569 ) {
1570 /* no NODATA, set to minimum possible value */
1571 if (!band->hasnodata)
1572 pixval = minval;
1573 /* has NODATA, use NODATA */
1574 else
1575 pixval = band->nodataval;
1576 RASTER_DEBUGF(4, "NODATA pixel outside band extent: (x, y, val) = (%d, %d, %f)", _x, _y, pixval);
1577 inextent = 0;
1578 isnodata = 1;
1579 }
1580 else {
1581 if (rt_band_get_pixel(
1582 band,
1583 _x, _y,
1584 &pixval,
1585 &isnodata
1586 ) != ES_NONE) {
1587 rterror("rt_band_get_nearest_pixel: Could not get pixel value");
1588 if (count) rtdealloc(*npixels);
1589 return -1;
1590 }
1591 RASTER_DEBUGF(4, "Pixel: (x, y, val) = (%d, %d, %f)", _x, _y, pixval);
1592 inextent = 1;
1593 }
1594
1595 /* use pixval? */
1596 if (!exclude_nodata_value || (exclude_nodata_value && !isnodata)) {
1597 /* add pixel to result set */
1598 RASTER_DEBUGF(4, "Adding pixel to set of nearest pixels: (x, y, val) = (%d, %d, %f)", _x, _y, pixval);
1599 count++;
1600
1601 if (*npixels == NULL)
1602 *npixels = (rt_pixel) rtalloc(sizeof(struct rt_pixel_t) * count);
1603 else
1604 *npixels = (rt_pixel) rtrealloc(*npixels, sizeof(struct rt_pixel_t) * count);
1605 if (*npixels == NULL) {
1606 rterror("rt_band_get_nearest_pixel: Could not allocate memory for nearest pixel(s)");
1607 return -1;
1608 }
1609
1610 npixel = &((*npixels)[count - 1]);
1611 npixel->x = _x;
1612 npixel->y = _y;
1613 npixel->value = pixval;
1614
1615 /* special case for when outside band extent */
1616 if (!inextent && !band->hasnodata)
1617 npixel->nodata = 1;
1618 else
1619 npixel->nodata = 0;
1620 }
1621
1622 (*_min)++;
1623 }
1624 }
1625 }
1626
1627 /* distance threshholds met */
1628 if (_d[0] >= distance[0] && _d[1] >= distance[1])
1629 break;
1630 else if (d0 && count)
1631 break;
1632 }
1633 while (1);
1634
1635 RASTER_DEBUGF(3, "Nearest pixels in return: %d", count);
1636
1637 return count;
1638}
FALSE
#define FALSE
Definition dbfopen.c:168
rterror
void rterror(const char *fmt,...)
Wrappers used for reporting errors and info.
Definition rt_context.c:199
rtalloc
void * rtalloc(size_t size)
Wrappers used for managing memory.
Definition rt_context.c:171
RASTER_DEBUG
#define RASTER_DEBUG(level, msg)
Definition librtcore.h:295
RASTER_DEBUGF
#define RASTER_DEBUGF(level, msg,...)
Definition librtcore.h:299
rt_pixtype_get_min_value
double rt_pixtype_get_min_value(rt_pixtype pixtype)
Return minimum value possible for pixel type.
Definition rt_pixel.c:148
rt_pixel
struct rt_pixel_t * rt_pixel
Definition librtcore.h:147
rt_pixtype_name
const char * rt_pixtype_name(rt_pixtype pixtype)
Definition rt_pixel.c:110
ES_NONE
@ ES_NONE
Definition librtcore.h:180
rtrealloc
void * rtrealloc(void *mem, size_t size)
Definition rt_context.c:179
rtdealloc
void rtdealloc(void *mem)
Definition rt_context.c:186
distance
static double distance(double x1, double y1, double x2, double y2)
Definition lwtree.c:1032
genraster.count
int count
Definition genraster.py:57
rt_band_get_pixel
rt_errorstate rt_band_get_pixel(rt_band band, int x, int y, double *value, int *nodata)
Get pixel value.
Definition rt_band.c:1221
rt_pixel_t::y
int y
Definition librtcore.h:2336
rt_pixel_t::value
double value
Definition librtcore.h:2339
rt_pixel_t::nodata
uint8_t nodata
Definition librtcore.h:2338
rt_pixel_t::x
int x
Definition librtcore.h:2335
rt_pixel_t
Definition librtcore.h:2334

References distance(), ES_NONE, FALSE, rt_pixel_t::nodata, RASTER_DEBUG, RASTER_DEBUGF, rt_band_get_pixel(), rt_pixtype_get_min_value(), rt_pixtype_name(), rtalloc(), rtdealloc(), rterror(), rtrealloc(), rt_pixel_t::value, rt_pixel_t::x, and rt_pixel_t::y.

Referenced by RASTER_nearestValue(), RASTER_neighborhood(), rt_raster_iterator(), test_band_get_nearest_pixel(), and test_pixel_set_to_array().

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