Class: QgsScaleCalculator

Calculates scale for a given combination of canvas size, map extent, and monitor dpi.

class qgis.core.QgsScaleCalculator[source]

Bases: object

__init__(dpi: float = 0, mapUnits: Qgis.DistanceUnit = Qgis.DistanceUnit.Meters)

Constructor

Parameters:

  • dpi (float = 0) – Monitor resolution in dots per inch

  • mapUnits (Qgis.DistanceUnit = Qgis.DistanceUnit.Meters) – Units of the data on the map

__init__(a0: QgsScaleCalculator)
Parameters:

a0 (QgsScaleCalculator)

calculate(self, mapExtent: QgsRectangle, canvasWidth: float) → float[source]

Calculate the scale denominator.

Parameters:

  • mapExtent (QgsRectangle) – QgsRectangle containing the current map extent. Units are specified by mapUnits().

  • canvasWidth (float) – Width of the map canvas in pixel (physical) units

Return type:

float

Returns:

scale denominator of current map view, e.g. 1000.0 for a 1:1000 map.

calculateGeographicDistance(self, mapExtent: QgsRectangle) → float[source]

Calculate the distance between two points in geographic coordinates. Used to calculate scale for map views with geographic (decimal degree) data.

Parameters:

mapExtent (QgsRectangle) – QgsRectangle containing the current map extent

Return type:

float

calculateImageSize(self, mapExtent: QgsRectangle, scale: float) → QSizeF[source]

Calculate the image size in pixel (physical) units.

Parameters:

  • mapExtent (QgsRectangle) – QgsRectangle containing the current map extent. Units are specified by mapUnits()

  • scale (float) – Scale denominator, e.g. 1000.0 for a 1:1000 map

Return type:

QSizeF

Returns:

image size

Added in version 3.24.

dpi(self) → float[source]

Returns the DPI (dots per inch) used in scale calculations.

See also

setDpi()

Return type:

float

mapUnits(self) → Qgis.DistanceUnit[source]

Returns current map units.

See also

setMapUnits()

Return type:

Qgis.DistanceUnit

setDpi(self, dpi: float)[source]

Sets the dpi (dots per inch) for the output resolution, to be used in scale calculations.

See also

dpi()

Parameters:

dpi (float)

setMapUnits(self, mapUnits: Qgis.DistanceUnit)[source]

Set the map units.

See also

mapUnits()

Parameters:

mapUnits (Qgis.DistanceUnit)