Class: QgsClipper

Trims lines and polygons to within a rectangular region.

The functions in this class are likely to be called from within a render loop and hence need to as CPU efficient as possible.

The main purpose of the functions in this class are to trim lines and polygons to lie within a rectangular region. This is necessary for drawing items to an X11 display which have a limit on the magnitude of the screen coordinates (+/- 32768, i.e. 16 bit integer).

Static Methods

clipLineSegment

Clips a line segment to a rectangle.

clippedLine

Takes a linestring and clips it to clipExtent

trimFeature

Trims the given feature to a rectangular box.

trimPolygon

Trims the given polygon to a rectangular box, by modifying the given polygon in place.

Attributes

MAX_X

Maximum X-coordinate of the rectangular box used for clipping.

MAX_Y

Maximum Y-coordinate of the rectangular box used for clipping.

MIN_X

Minimum X-coordinate of the rectangular box used for clipping.

MIN_Y

Minimum Y-coordinate of the rectangular box used for clipping.

XMax

XMin

YMax

YMin

ZMax

ZMin

class qgis.core.QgsClipper[source]

Bases: object

class Boundary

Bases: int

MAX_X: float = 16000.0

Maximum X-coordinate of the rectangular box used for clipping.

MAX_Y: float = 16000.0

Maximum Y-coordinate of the rectangular box used for clipping.

MIN_X: float = -16000.0

Minimum X-coordinate of the rectangular box used for clipping.

MIN_Y: float = -16000.0

Minimum Y-coordinate of the rectangular box used for clipping.

XMax = 0
XMin = 1
YMax = 2
YMin = 3
ZMax = 4
ZMin = 5
static clipLineSegment(left: float, right: float, bottom: float, top: float, x0: float, y0: float, x1: float, y1: float)[source]

Clips a line segment to a rectangle.

An implementation of the ‘Fast clipping’ algorithm (Sobkow et al. 1987, Computers & Graphics Vol.11, 4, p.459-467).

Parameters:

  • left (float) – x-coordinate of left side of rectangle

  • right (float) – x-coordinate of right side of rectangle

  • bottom (float) – y-coordinate of bottom side of rectangle

  • top (float) – y-coordinate of top side of rectangle

  • x0 (float) – x-coordinate of start of line

  • y0 (float) – y-coordinate of start of line

  • x1 (float) – x-coordinate of end of line

  • y1 (float) -> (bool) – y-coordinate of end of line

Returns:

True if line was clipped.

Added in version 3.26.

static clippedLine(curve: QgsCurve, clipExtent: QgsRectangle) → QPolygonF[source]

Takes a linestring and clips it to clipExtent

Parameters:
Return type:

QPolygonF

Returns:

clipped line coordinates

static clippedLine(curve: QPolygonF, clipExtent: QgsRectangle) → QPolygonF[source]

Takes a 2D curve and clips it to clipExtent.

Parameters:

  • curve (QPolygonF) – the linestring

  • clipExtent (QgsRectangle) – clipping bounds

Return type:

QPolygonF

Returns:

clipped line coordinates

Added in version 3.16.

static trimFeature(x: Iterable[float], y: Iterable[float], shapeOpen: bool)[source]

Trims the given feature to a rectangular box. Returns the trimmed feature in x and y. The shapeOpen parameter determines whether the function treats the points as a closed shape (polygon), or as an open shape (linestring).

Note

not available in Python bindings on android

Parameters:

  • x (Iterable[float])

  • y (Iterable[float])

  • shapeOpen (bool)

static trimPolygon(pts: QPolygonF, clipRect: QgsRectangle)[source]

Trims the given polygon to a rectangular box, by modifying the given polygon in place.

Parameters:

  • pts (QPolygonF) – polygon as 2D coordinates

  • clipRect (QgsRectangle) – clipping rectangle