Hi all,
I'm trying to use the raster functions for the first time. I have a
simple black and white image with some polygons drawn on it. and I want
to extract the polygons as geometry.
$ gdalinfo -hist 12322240_lines.png
Driver: PNG/Portable Network Graphics
Files: 12322240_lines.png
12322240_lines.png.aux.xml
Size is 600, 800
Coordinate System is `'
Corner Coordinates:
Upper Left ( 0.0, 0.0)
Lower Left ( 0.0, 800.0)
Upper Right ( 600.0, 0.0)
Lower Right ( 600.0, 800.0)
Center ( 300.0, 400.0)
Band 1 Block=600x1 Type=Byte, ColorInterp=Gray
256 buckets from -0.5 to 255.5:
474137 5863 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
Image Structure Metadata:
NBITS=1
the background is the 474137bucket and the line work is the 5863 bucket.
$ raster2pgsql -t auto -P -c -f img -F -n file -I -M *.png |
/usr/lib/postgresql/9.5/bin/psql -U postgres -h localhost -p 5435
test_sketch
I'm loading 2 PNG images in this example, about ultimately I will have
100-1000s of images to process and extract the line work.
SELECT (md).*, (bmd).*
FROM (SELECT ST_Metadata(img) AS md,
ST_BandMetadata(img) AS bmd
FROM "12322240_lines" LIMIT 1
) foo;
-- 0;0;30;32;1;-1;0;0;0;1;"8BUI";;f;""
select rid, val, st_astext(geom) as wkt
from (
select rid, dp.*
from "12322240_lines", lateral st_dumpaspolygons(img, 1, true) as dp
) as foo;
This generates 1349 rows. So it appears to be processing these an a tile
by tile basis not on the whole image. How do I get the polygons that are
represented by the sketch. Assuming that the sketch lines are 1 or 2
pixels wide, I presume that I would get the polygon around those pixels.
Do I need to then skeletonize that to get the original lines?
select * from "12322240_lines";
generates 100 rows.
Any thoughts on how to best approach this would be appreciated.
Thanks,
-Steve
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