Class: QgsScaleCalculator¶

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

The calculation defaults to using the scale calculated horizontally across the center of the map, however this may be changed by calling setMethod().

Methods

`calculate`	Calculate the scale denominator.
`calculateGeographicDistance`	Calculate the distance in meters, horizontally across the specified map extent (in geographic coordinates).
`calculateGeographicDistanceAtLatitude`	Calculate the distance in meters, horizontally between two longitudes at a specified latitude.
`calculateImageSize`	Calculate the image size in pixel (physical) units.
`dpi`	Returns the DPI (dots per inch) used in scale calculations.
`mapUnits`	Returns current map units.
`method`	Returns the method to use for map scale calculations.
`setDpi`	Sets the dpi (dots per inch) for the output resolution, to be used in scale calculations.
`setMapUnits`	Set the map units.
`setMethod`	Sets the method to use for map scale calculations.

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 in meters, horizontally across the specified map extent (in geographic coordinates).

Used to calculate scale for map views with geographic (decimal degree) data.

This method respects the scale method().

Parameters:: mapExtent (QgsRectangle) – the map extent, in geographic (degrees) coordinates
Return type:: float
Returns:: distance in meters across the map extent

calculateGeographicDistanceAtLatitude(self, latitude: float, longitude1: float, longitude2: float) → float[source]¶

Calculate the distance in meters, horizontally between two longitudes at a specified latitude.

Used to calculate scale for map views with geographic (decimal degree) data.

Parameters:

latitude (float) – latitude (in degrees) to calculate distance at
longitude1 (float) – first longitude (left side of map, or x-minimum) to calculate distance between
longitude2 (float) – second longitude (right side of map, or x-maximum) to calculate distance between

Return type:

float

Returns:

distance in meters between the two longitudes

Added in version 3.44.

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: