17
votes
How to speed up raster to polygon conversion in R?
There is a "new" method from the stars package, which revolutionized the workflow for me (I was using the gdal_polygonizeR function previously). It has been faster than the John Baumgartner solution ...
- 374
9
votes
Accepted
Convert a group of lines into a single polygone to style it
If you need to handle the polylines just for styling, you don't need to manipulate the geometry.
E.g. you want to get rid of overlapping edges at a street intersection, you can to this by activating "...
- 827
9
votes
Accepted
Cannot select input layers for the "Polygonize" tool in QGIS
When you search for Polygonize in the Processing Toolbox, there appear several tools.
1) Polygonize tool converts line layer to polygon layer, turning an area inside three line segments into a ...
- 31.2k
8
votes
Accepted
Polygonizing a raster yields lots of little squares?
The reason for this is that while you see yellow pixels, or pink pixels, QGIS sees thousands of discrete colours
Zoom in really close to scanned map you'll see lots of noise - neighbouring pixels ...
- 20.6k
8
votes
Converting raster to vector and creating polygons based on each pixel in QGIS
Yet another option would be SAGA Raster values to points tool (QGIS Processing Toolbox | SAGA | Vector <-> raster).
Choose [1] cells as Type option.
SAGA - Raster values to points
note white ...
- 31.2k
8
votes
Accepted
Divide a polygon into multiple small polygons using a MultiLineString
You may not need to use this MultiLineString variable for what you aim at. This works:
from shapely.geometry import Polygon, LineString
from shapely.ops import linemerge, unary_union, polygonize
poly ...
- 10.3k
7
votes
Converting polyline to polygon in QGIS
Just a hint if you can't find the Polygonize tool. In my QGIS 2.18.3 installation (Windows) I could not find the Polygonize tool at Vector geometry tools within the Toolbox. It took me some time to ...
- 340
7
votes
Accepted
Create polygons (representing boundaries) from lines
Starting with nc borders from the example(st_read) code, I'll first make a set of lines like in your data and then put them back together again. So we start with 100 North Carolina polygons in a ...
- 66.5k
7
votes
Accepted
How to apply GDAL polygonize?
I downloaded the dataset you linked to and tested with the following script- it works ok for me.
In the following script, I left my own paths in for reference but you should of course change them to ...
- 23.1k
7
votes
Accepted
How to extract the boundaries of Shapely MultiPoint?
For a grid-like multipoint, you can use buffer method to get the boundary of points as a polygon. For a multipoint geometry with 100 meters between each point as in the image, the following script ...
- 78k
6
votes
Accepted
Convert multiple polylines to polygons in QGIS
Using QGIS processing: v.clean [snap]
Polyline test
The threshold is determined by attempts:
final results
To get the polygons: polygonize
polygons
- 4,520
6
votes
Accepted
sf lines to polygons with holes
The problem is that you have created a GEOMETRYCOLLECTION which can be an unstructured set of linear features, in other words there's no concept of holes and islands.
What you want is a MULTIPOLYGON....
- 66.5k
6
votes
Accepted
Vectorize raster
I found a solution using USGS landcover dataset and gdal_sieve . The raw dataset looks like this:
And using gdal_sieve led to that:
Which is exactly what I wanted :) . Now I "just" have to choose ...
- 604
6
votes
Accepted
Transforming line into polygon with Geometry Generator
Let's assume there is a polyline layer "line", see image below.
Proceed with RMT > Symbology > Single Symbol > Line > Geometry Generator
Use the following code make_polygon($...
- 34k
6
votes
Accepted
Merging cluster of points into polygons
This will work when each cluster has an attribute that defines it.
If there is no such attribute, you can achieve it using the "DBSCAN clustering" geoalgorithm.
Clusters point features ...
- 34k
6
votes
Accepted
How to polygonize raster with range of values?
What you want to do is the re-classify the raster before polygonizing. You can GRASS tool r.recode for that (available in QGIS).
For a solution with raster calculator, see below.
Using GRASS r.recode
...
- 74.9k
6
votes
Accepted
"UnicodeDecodeError: 'utf-8' codec can't decode byte 0x82 in position 85: invalid start byte" error when polygonizing WMS in QGIS
You cannot polygonize a WMS layer with QGIS. As you can see from the generated gdal_polygonize command, the name of the input raster is obscure.
"crs=EPSG:3857&dpiMode=7&format=image/png&...
- 69k
5
votes
Converting polyline to polygon in QGIS
I had the same unwanted output and after doing some research it seems the cause can vary.
My case was I had some polyline layers with very, very small gaps (in which some fragments were formed by two ...
- 10.3k
5
votes
Converting polyline to polygon in QGIS
If the polylines overlap each other, Polygonize tool cannot handle it as follows:
However Lines to polygons tool works as expected as follows:
- 151
5
votes
Gdal Polygonize, empty attribute table
Found out that the reason the attribute table was empty was due to
gdal.Polygonize( band, None, outLayer, -1, [], callback=None )
Updated it to
gdal.Polygonize( band, None, outLayer, 0, [], ...
- 81
5
votes
Accepted
Smoothing raster with binary cell values
Similar to what @WhiteboxDev suggested, another filter type that could be used is a sieve filter. Instead of looking at whether the 0s or 1s "win" for a given region, it looks at the number of ...
- 6,526
5
votes
Smoothing raster with binary cell values
In addition to the use of a majority filter, there is another alternative approach that I will list below. This approach is more involved than simply filtering the raster and should only be used when ...
- 11.1k
5
votes
Extracting polygons from scanned GeoRef images based on colours in QGIS
You can get pretty close with:
"Raster calculator". The turquoise areas have a red band value of about 100-120 (in my downloaded copy of your raster) the other colors a lot less or more, I ...
- 77.8k
5
votes
QGIS - How do I select features in a particular location precisely, the location is a raster
Open the Raster calculator tool and use this expression to create a mask, "layer@band" != no-data. Replace layer with the name of your raster, band with the number of your band and no-data ...
- 4,050
5
votes
Accepted
Polygonize error
I could re-produce the error with QGIS 3.35, installed with OSGeo4W.
The command log shows that with the default setting QGIS tries to save the polygonozed result into an Interlis 2 file. This format ...
- 69k
4
votes
Convert a group of lines into a single polygone to style it
If the symbol levels don't work for you (not sure when it was implemented), you can simply duplicate the layer, style the first with 1mm red, and the second with 2mm black:
The order in the legend ...
- 77.1k
4
votes
Accepted
QGIS 2.18 Polygonize (raster to vector)
As you have deduced already the QGIS polygonize utility is a GUI for GDAL_Polygonize which briefly explains the use of a mask:
-mask filename: Use the first band of the specified file as a validity ...
- 25.7k
4
votes
Accepted
Batch Polygonize rasters into shp file using gdal_polygonize.py but no result?
As said by Michael Stimson from the comments, here's the answer for my own question:
import subprocess, glob
script = "/usr/bin/gdal_polygonize.py"
for raster in glob.glob("/data/brent/GAUP/Jul21_17-...
- 772
4
votes
Converting raster to vector and creating polygons based on each pixel in QGIS
Alternatively you can do it directly with OpenJUMP Plus.
Open your raster as a Sextante raster layer and use this tool
As a result you'll get a polygon layer that contains the pixel values as ...
- 69k
4
votes
Converting raster to vector and creating polygons based on each pixel in QGIS
Since QGIS 3.4 there is an algorithm called "Raster pixels to polygons".
You can find it in the Processing Toolbox -> Vector creation -> Raster pixels to polygons
For more details ...
- 4,638
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