Finding algorithms of QGIS commands?
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I'm looking for the algorithms (the math) used by QGIS but I can't find any documentation about it
The ones I'm looking for are:
- Minimum bounding geometry (convex hull)
- Clip a polygon by a polygon
Does anyone knows where I can find them?
qgis algorithm documentation
edited Mar 12 at 10:57
Vince
14.8k32850
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
add a comment |
I'm looking for the algorithms (the math) used by QGIS but I can't find any documentation about it
The ones I'm looking for are:
- Minimum bounding geometry (convex hull)
- Clip a polygon by a polygon
Does anyone knows where I can find them?
qgis algorithm documentation
edited Mar 12 at 10:57
Vince
14.8k32850
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
docs.qgis.org/testing/en/docs/user_manual/processing/…
– Fran Raga
Mar 12 at 10:31
5
It's open source software. As the the old spaghetti sauce commercial used to say, "It's in there."
– Vince
Mar 12 at 11:01
add a comment |
I'm looking for the algorithms (the math) used by QGIS but I can't find any documentation about it
The ones I'm looking for are:
- Minimum bounding geometry (convex hull)
- Clip a polygon by a polygon
Does anyone knows where I can find them?
qgis algorithm documentation
edited Mar 12 at 10:57
Vince
14.8k32850
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
I'm looking for the algorithms (the math) used by QGIS but I can't find any documentation about it
The ones I'm looking for are:
- Minimum bounding geometry (convex hull)
- Clip a polygon by a polygon
Does anyone knows where I can find them?
qgis algorithm documentation
qgis algorithm documentation
edited Mar 12 at 10:57
Vince
14.8k32850
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
edited Mar 12 at 10:57
Vince
14.8k32850
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
edited Mar 12 at 10:57
Vince
14.8k32850
edited Mar 12 at 10:57
Vince
14.8k32850
edited Mar 12 at 10:57
Vince
14.8k32850
14.8k32850
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
asked Mar 12 at 10:04
Koen VenkenKoen Venken
554
554
docs.qgis.org/testing/en/docs/user_manual/processing/…
– Fran Raga
Mar 12 at 10:31
5
It's open source software. As the the old spaghetti sauce commercial used to say, "It's in there."
– Vince
Mar 12 at 11:01
add a comment |
docs.qgis.org/testing/en/docs/user_manual/processing/…
– Fran Raga
Mar 12 at 10:31
5
It's open source software. As the the old spaghetti sauce commercial used to say, "It's in there."
– Vince
Mar 12 at 11:01
docs.qgis.org/testing/en/docs/user_manual/processing/…
– Fran Raga
Mar 12 at 10:31
docs.qgis.org/testing/en/docs/user_manual/processing/…
– Fran Raga
Mar 12 at 10:31
5
5
It's open source software. As the the old spaghetti sauce commercial used to say, "It's in there."
– Vince
Mar 12 at 11:01
It's open source software. As the the old spaghetti sauce commercial used to say, "It's in there."
– Vince
Mar 12 at 11:01
add a comment |
2 Answers
2
active
oldest
votes
The "minimum bounding geometry" and "clip polygon" algorithms in QGIS are implemented in /python/plugins/processing/algs/qgis/MinimumBoundingGeometry.py and /src/analysis/processing/qgsalgorithmclip.cpp.
If you follow through the source of these, you'll find that they rely on geometry-related functions from a C++ class called QgsGeometry, specifically QgsGeometry::convexHull() and QgsGeometry::intersection(). The "clip" algorithm also contains additional logic for building a union of geometries to form a mask polygon, as well as testing for points within the polygon, in the case of non-polygon vectors.
Reading through the QgsGeometry class shows that the actual algorithms themselves are implemented in a library called GEOS. GEOS is a C++ port of a Java library called the JTS Topology Suite, which implements a suite of geometry-related algorithms.
The core of the ConvexHull algorithm from GEOS is implemented here using an algorithm called Graham's scan. The implementation of intersection in GEOS is a bit more complicated and spread out, but here's a place to start looking. GEOS supports various binary operations between geometries and "intersection" is only one of them.
In general, GEOS is the place to look for the implementations of the various vector algorithms in QGIS, but there are also some raster algorithms in QGIS which are implemented by the GDAL library.
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
add a comment |
You can check the algorithms at QGIS Github and find scripts for all the tools such as the minimum bounding geometry.
answered Mar 12 at 10:13
JosephJoseph
59k7102207
1
While these links are good starting points, it's worth noting that the algorithms themselves aren't in the QGIS source repository.
– Candy Gumdrop
Mar 12 at 13:24
@CandyGumdrop - Thanks for providing a comprehensive answer :)
– Joseph
Mar 13 at 10:14
add a comment |
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2 Answers
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active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
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oldest
votes
The "minimum bounding geometry" and "clip polygon" algorithms in QGIS are implemented in /python/plugins/processing/algs/qgis/MinimumBoundingGeometry.py and /src/analysis/processing/qgsalgorithmclip.cpp.
If you follow through the source of these, you'll find that they rely on geometry-related functions from a C++ class called QgsGeometry, specifically QgsGeometry::convexHull() and QgsGeometry::intersection(). The "clip" algorithm also contains additional logic for building a union of geometries to form a mask polygon, as well as testing for points within the polygon, in the case of non-polygon vectors.
Reading through the QgsGeometry class shows that the actual algorithms themselves are implemented in a library called GEOS. GEOS is a C++ port of a Java library called the JTS Topology Suite, which implements a suite of geometry-related algorithms.
The core of the ConvexHull algorithm from GEOS is implemented here using an algorithm called Graham's scan. The implementation of intersection in GEOS is a bit more complicated and spread out, but here's a place to start looking. GEOS supports various binary operations between geometries and "intersection" is only one of them.
In general, GEOS is the place to look for the implementations of the various vector algorithms in QGIS, but there are also some raster algorithms in QGIS which are implemented by the GDAL library.
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
add a comment |
The "minimum bounding geometry" and "clip polygon" algorithms in QGIS are implemented in /python/plugins/processing/algs/qgis/MinimumBoundingGeometry.py and /src/analysis/processing/qgsalgorithmclip.cpp.
If you follow through the source of these, you'll find that they rely on geometry-related functions from a C++ class called QgsGeometry, specifically QgsGeometry::convexHull() and QgsGeometry::intersection(). The "clip" algorithm also contains additional logic for building a union of geometries to form a mask polygon, as well as testing for points within the polygon, in the case of non-polygon vectors.
Reading through the QgsGeometry class shows that the actual algorithms themselves are implemented in a library called GEOS. GEOS is a C++ port of a Java library called the JTS Topology Suite, which implements a suite of geometry-related algorithms.
The core of the ConvexHull algorithm from GEOS is implemented here using an algorithm called Graham's scan. The implementation of intersection in GEOS is a bit more complicated and spread out, but here's a place to start looking. GEOS supports various binary operations between geometries and "intersection" is only one of them.
In general, GEOS is the place to look for the implementations of the various vector algorithms in QGIS, but there are also some raster algorithms in QGIS which are implemented by the GDAL library.
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
add a comment |
The "minimum bounding geometry" and "clip polygon" algorithms in QGIS are implemented in /python/plugins/processing/algs/qgis/MinimumBoundingGeometry.py and /src/analysis/processing/qgsalgorithmclip.cpp.
If you follow through the source of these, you'll find that they rely on geometry-related functions from a C++ class called QgsGeometry, specifically QgsGeometry::convexHull() and QgsGeometry::intersection(). The "clip" algorithm also contains additional logic for building a union of geometries to form a mask polygon, as well as testing for points within the polygon, in the case of non-polygon vectors.
Reading through the QgsGeometry class shows that the actual algorithms themselves are implemented in a library called GEOS. GEOS is a C++ port of a Java library called the JTS Topology Suite, which implements a suite of geometry-related algorithms.
The core of the ConvexHull algorithm from GEOS is implemented here using an algorithm called Graham's scan. The implementation of intersection in GEOS is a bit more complicated and spread out, but here's a place to start looking. GEOS supports various binary operations between geometries and "intersection" is only one of them.
In general, GEOS is the place to look for the implementations of the various vector algorithms in QGIS, but there are also some raster algorithms in QGIS which are implemented by the GDAL library.
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
The "minimum bounding geometry" and "clip polygon" algorithms in QGIS are implemented in /python/plugins/processing/algs/qgis/MinimumBoundingGeometry.py and /src/analysis/processing/qgsalgorithmclip.cpp.
If you follow through the source of these, you'll find that they rely on geometry-related functions from a C++ class called QgsGeometry, specifically QgsGeometry::convexHull() and QgsGeometry::intersection(). The "clip" algorithm also contains additional logic for building a union of geometries to form a mask polygon, as well as testing for points within the polygon, in the case of non-polygon vectors.
Reading through the QgsGeometry class shows that the actual algorithms themselves are implemented in a library called GEOS. GEOS is a C++ port of a Java library called the JTS Topology Suite, which implements a suite of geometry-related algorithms.
The core of the ConvexHull algorithm from GEOS is implemented here using an algorithm called Graham's scan. The implementation of intersection in GEOS is a bit more complicated and spread out, but here's a place to start looking. GEOS supports various binary operations between geometries and "intersection" is only one of them.
In general, GEOS is the place to look for the implementations of the various vector algorithms in QGIS, but there are also some raster algorithms in QGIS which are implemented by the GDAL library.
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
edited Mar 19 at 8:39
Ian Turton♦
50.3k548119
50.3k548119
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
answered Mar 12 at 12:16
Candy GumdropCandy Gumdrop
38114
38114
add a comment |
add a comment |
You can check the algorithms at QGIS Github and find scripts for all the tools such as the minimum bounding geometry.
answered Mar 12 at 10:13
JosephJoseph
59k7102207
1
While these links are good starting points, it's worth noting that the algorithms themselves aren't in the QGIS source repository.
– Candy Gumdrop
Mar 12 at 13:24
@CandyGumdrop - Thanks for providing a comprehensive answer :)
– Joseph
Mar 13 at 10:14
add a comment |
You can check the algorithms at QGIS Github and find scripts for all the tools such as the minimum bounding geometry.
answered Mar 12 at 10:13
JosephJoseph
59k7102207
1
While these links are good starting points, it's worth noting that the algorithms themselves aren't in the QGIS source repository.
– Candy Gumdrop
Mar 12 at 13:24
@CandyGumdrop - Thanks for providing a comprehensive answer :)
– Joseph
Mar 13 at 10:14
add a comment |
You can check the algorithms at QGIS Github and find scripts for all the tools such as the minimum bounding geometry.
answered Mar 12 at 10:13
JosephJoseph
59k7102207
You can check the algorithms at QGIS Github and find scripts for all the tools such as the minimum bounding geometry.
answered Mar 12 at 10:13
JosephJoseph
59k7102207
answered Mar 12 at 10:13
JosephJoseph
59k7102207
answered Mar 12 at 10:13
JosephJoseph
59k7102207
answered Mar 12 at 10:13
JosephJoseph
59k7102207
59k7102207
1
While these links are good starting points, it's worth noting that the algorithms themselves aren't in the QGIS source repository.
– Candy Gumdrop
Mar 12 at 13:24
@CandyGumdrop - Thanks for providing a comprehensive answer :)
– Joseph
Mar 13 at 10:14
add a comment |
1
While these links are good starting points, it's worth noting that the algorithms themselves aren't in the QGIS source repository.
– Candy Gumdrop
Mar 12 at 13:24
@CandyGumdrop - Thanks for providing a comprehensive answer :)
– Joseph
Mar 13 at 10:14
1
1
While these links are good starting points, it's worth noting that the algorithms themselves aren't in the QGIS source repository.
– Candy Gumdrop
Mar 12 at 13:24
While these links are good starting points, it's worth noting that the algorithms themselves aren't in the QGIS source repository.
– Candy Gumdrop
Mar 12 at 13:24
@CandyGumdrop - Thanks for providing a comprehensive answer :)
– Joseph
Mar 13 at 10:14
@CandyGumdrop - Thanks for providing a comprehensive answer :)
– Joseph
Mar 13 at 10:14
add a comment |
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docs.qgis.org/testing/en/docs/user_manual/processing/…
– Fran Raga
Mar 12 at 10:31
5
It's open source software. As the the old spaghetti sauce commercial used to say, "It's in there."
– Vince
Mar 12 at 11:01