Add QgsAbstractGeometry::simplifyByDistance, which is a direct
port of GEOS Douglas Peucker algorithm.
This is a trivial algorithm to implement, and we benefit from
avoiding the conversion to/from GEOS geometries.
The comparisons among QGIS were conducted on coordinates using a fixed epsilon:
specifically, 1e-8 for QgsPoint and the default value for qgsDoubleNear: 4 *
DBL_EPSILON.
Initially, I've standardized its use to 1e-8 universally; it's already
significantly adequate for our Cartesian cases (1e-3 should suffice for many),
potentially fitting just right for geographical contexts.
Furthermore, in response to precision concerns, we're using the fuzzyEqual
and fuzzyDistanceEqual methods. These methods enable users/developers to
compare geometries more easily and with a given precision.
The API remains intact as operator==/equals() have been shifted into fuzzyEqual
(with an epsilon of 1e-8).
To consolidate the code between fuzzyEqual and fuzzyDistanceEqual, helper
functions, fuzzyHelpers, have been introduced following the logic of the
respective segments to be executed.
This enum was forcing an include of qgscoordinatetransform.h within the
widely used qgsabstractgeometry.h header, causing an absolute explosion
of includes of a bunch of very heavy header classes all across QGIS. By
removing the forced include we can avoid a ton of unwanted includes
and make wider use of forward declarations...
Returns a reference to the simplest lossless representation of this geometry,
e.g. if the geometry is a multipart geometry type with a single member geometry,
a reference to that part will be returned.
This method employs the following logic:
- For multipart geometries containing a single part only a direct reference to that part will be returned.
- For compound curve geometries containing a single curve only a direct reference to that curve will be returned.
This method returns a reference only, and does not involve any geometry cloning.
A port of the equivalent method from GEOS, but with added support
for curved geometries and M values
Reorganizes the geometry into a normalized form (or "canonical" form).
Polygon rings will be rearranged so that their starting vertex is
the lower left and ring orientation follows the right hand rule, collections
are ordered by geometry type, and other normalization techniques are applied.
The resultant geometry will be geometrically equivalent to the original geometry.
Allows for comparison of geometry objects, e.g. to allow for stable
sorting of them.
Ported from the GEOS equivalent method, but with addition of support
for M values and curved geometry types
to transform the vertices of a QgsAbstractGeometry
E.g.
class Transformer(QgsAbstractGeometryTransformer):
def transformPoint(self, x, y, z, m):
return True, x * 2, y + 1, z, m
transformer = Transformer()
g = QgsGeometry.fromWkt('LineString(3 0, 10 0, 10 10)')
g.get().transform(transformer)
print(g.asWkt()) # 'LineString (6 1, 20 1, 20 11)'
... you are too slow and QJson API is so ugly.
Now using this wonderful json lib:
https://github.com/nlohmann/json
Results in release mode (QJson tests are not shown but
QJson was even slower than string concat).
PASS : TestQgsJsonUtils::testExportAttributesJson(Use json)
RESULT : TestQgsJsonUtils::testExportAttributesJson():"Use json":
0.0022 msecs per iteration (total: 75, iterations: 32768)
PASS : TestQgsJsonUtils::testExportAttributesJson(Use old string concat)
RESULT : TestQgsJsonUtils::testExportAttributesJson():"Use old string concat":
0.0032 msecs per iteration (total: 54, iterations: 16384)
PASS : TestQgsJsonUtils::testExportFeatureJson(Use json)
RESULT : TestQgsJsonUtils::testExportFeatureJson():"Use json":
0.011 msecs per iteration (total: 96, iterations: 8192)
PASS : TestQgsJsonUtils::testExportFeatureJson(Use old string concat)
RESULT : TestQgsJsonUtils::testExportFeatureJson():"Use old string concat":
0.015 msecs per iteration (total: 64, iterations: 4096)
PASS : TestQgsJsonUtils::testExportGeomToJson(Use json)
RESULT : TestQgsJsonUtils::testExportGeomToJson():"Use json":
0.76 msecs per iteration (total: 98, iterations: 128)
PASS : TestQgsJsonUtils::testExportGeomToJson(Use old string concat)
RESULT : TestQgsJsonUtils::testExportGeomToJson():"Use old string concat":
0.85 msecs per iteration (total: 55, iterations: 64)
PASS : TestQgsJsonUtils::cleanupTestCase()
Also avoid massive long __repr__ strings for complex geometries,
as these can flood the Python console (and first aid plugin),
and aren't useful for debugging anyway.
Refs #14640
All your uses of toUtf8().data() actually just need a const char*
So use constData() that is semantically more correct, and documented
to be faster.
From http://doc.qt.io/qt-5/qbytearray.html#data
"For read-only access, constData() is faster because it never
causes a deep copy to occur."
Because:
- Exactly follows curves and doesn't require segmentizing input geometry
- Also interpolates z/m values if they are present in input geometry
- Is faster
Returns a new curve representing a substring of a curve, from
a start distance and end distance.
If z or m values are present, the output z and m will be interpolated using
the existing vertices' z or m values.
Handles curved geometries without loss.
