Interface CanvasState


  • public interface CanvasState
    Describe the current state of a canvas. The information contained by instances of this interface should only describe the viewing area or volume of the canvas and should not contain any state information regarding the data contained within it.

    When an instance of this class is returned from Canvas methods, a "snapshot" of the current state of the canvas is taken and the values will never change (even if the canvas changes state).

    Since:
    GeoAPI 2.2
    • Method Detail

      • getDisplayCRS

        CoordinateReferenceSystem getDisplayCRS()
        Returns the Coordinate Reference System associated with the display of the canvas. The display CRS has a Coordinate System corresponding to the geometry of the display device. For example flat video monitors are associated to cartesian CS while planetarium may be associated to spherical CS. Axis units are typically (but are not restricted to) some linear units like 1/72 of inch.

        This CRS can be implemented as a derived CRS based on the objective CRS. In such implementations, the display CRS changes after every zoom or translation action.

        Returns:
        the display Coordinate Reference System.
      • getObjectiveToDisplayTransform

        MathTransform getObjectiveToDisplayTransform()
        Returns the transform from objective to display CRS. If the later is implemented as a derived CRS, then this transform shall be equal to the following:
        getDisplayCRS().getConversionFromBase().getMathTransform()
        This transform is typically (but is not required to be) affine. When this transform is affine, then the scale factors (the coefficients on the matrix diagonal when there is no rotation or shear) are the map scale along the corresponding axis.
        Returns:
        the transform from objective to display CRS.