News & Updates

ENVI: Adding custom polygons to the display

Author: Daryl Atencio / Friday, October 28, 2016

A recent project I worked on required custom polygons – Controlled by my application – to be added to the ENVI display.  The following code defines an object class that allows the user to place a polygon in the ENVI display using window coordinates.  To run the application:

  1. Save the code that follows to a file named envi_polygon_example.pro
  2. Open and compile the file in the IDLDE
  3. Execute the following at the IDL command prompt

  4. envi_polygon_example

;------------------------------------------------------------------------------

;+

; Lifecycle method for destroying the object

;-

pro my_polygon::Cleanup

  compile_opt idl2, logical_predicate

  self->Destruct

end

 

;------------------------------------------------------------------------------

;+

; Cleans up the member variables of the object class

;-

pro my_polygon::Destruct

  compile_opt idl2, logical_predicate

  self->IDLmiManipGraphicOverlay::Cleanup

  self->IDLmiManipLayer::Cleanup

  self->IDLgrPolygon::Cleanup

end

 

;------------------------------------------------------------------------------

;+

; Lifecycle method for initializing the class

;

; :Returns:

;   1 if the object initializes successfully and 0 otherwise

;  

; :Params:

;   xy: in, optional, type="int"

;     a [2,n] array containing the [x,y] points in window coordinates

;  

; :Keywords:

;   POLYGONS: in, optional, type="int"

;     An integer array of one or more polygon descriptions.  See IDL help for

;     IDLgrPolygon for more information

;   _REF_EXTRA: Used to set properties of the inherited IDLgrPolygon

;-

function my_polygon::Init, xy, $

  POLYGONS=poly, $

  _REF_EXTRA=refExtra

  compile_opt idl2, logical_predicate

  void = self->IDLmiManipGraphicOverlay::Init(_EXTRA=refExtra)

  if ~void then begin

    return, 0

  endif

  self->InitializeDataspace

  self->SetupManipulatorGraphics

  self->InitializeGraphics

  if n_elements(xy) then begin

    self->SetProperty, DATA=xy, POLYGONS=poly

  endif

  if n_elements(refExtra) then begin

    self->SetProperty, _EXTRA=refExtra

  endif

  return, 1

end

 

;------------------------------------------------------------------------------

;+

; This method initializes the data space used by the graphics layer

;-

pro my_polygon::InitializeDataspace

  compile_opt idl2, logical_predicate

  e = envi(/CURRENT)

  eView = e->GetView()

  eView->GetProperty, _COMPONENT=ecfViewGroup

  oDS = ecfViewGroup->GetDescendants(BY_TYPE='DATASPACE', /FIRST_ONLY)

  self._oTargetDS = oDS

end

 

;------------------------------------------------------------------------------

;+

; Initializes the graphics components of the class

;-

pro my_polygon::InitializeGraphics

  compile_opt idl2, logical_predicate

  void = self->IDLgrPolygon::Init(COLOR=[255,0,0], /PRIVATE, THICK=2)

  self._oGrOverlay->IDLmiContainer::Add, self

end

 

;------------------------------------------------------------------------------

;+

; This method is for setting class properties

;-

pro my_polygon::SetProperty, $

  DATA=data, $

  POLYGONS=poly, $

  _REF_EXTRA=refExtra

  compile_opt idl2, logical_predicate

  if n_elements(data) then begin

    self->SetData, data, POLYGONS=poly

  endif

  if n_elements(refExtra) then begin

    self->IDLgrPolygon::SetProperty, _EXTRA=refExtra

    self->IDLmiManipLayer::SetProperty, _EXTRA=refExtra

  endif

end

 

;------------------------------------------------------------------------------

;+

; This method maps the points from window coordinates to map coordinates and

; adds the mapped points to the IDLgrPolygon.

;

; :Params:

;   xy: in, required, type="int"

;     A [2,n] array of points (In window coordinates) to be added to the polygon

;

; :Keywords:

;   POLYGONS: in, optional, type="int"

;     An integer array of one or more polygon descriptions.  See IDL help for

;     IDLgrPolygon for more information

;-

pro my_polygon::SetData, xy, $

  POLYGONS=poly

  compile_opt idl2, logical_predicate

  self._oTargetDS->WindowToVis, reform(xy[0,*]), reform(xy[1,*]), xVis, yVis

  self->IDLgrPolygon::SetProperty, DATA=transpose([[xVis],[yVis]]), $

    POLYGONS=poly

end

 

;------------------------------------------------------------------------------

;+

; Class structure definition

;-

pro my_polygon__define

  compile_opt idl2, logical_predicate

  void = {my_polygon                    $

    , inherits IDLmiManipGraphicOverlay $

    , inherits IDLmiManipLayer          $

    , inherits IDLgrPolygon             $

    }

end

 

;------------------------------------------------------------------------------

;+

;-

pro envi_polygon_example

  compile_opt idl2, logical_predicate

  e = envi(/CURRENT)

  if ~isa(e, 'envi') then begin

    e = envi()

  endif

  file = FILEPATH('qb_boulder_msi', ROOT_DIR=e.ROOT_DIR, SUBDIRECTORY=['data'])

  eRaster = e->OpenRaster(file)

  eView = e->GetView()

  eLayer = eView->CreateLayer(eRaster)

  xy = [[470,140],[560,140],[560,230],[470,230], $

    [750,115],[1200,115],[1200,665],[750,665]]

  conn = [4,0,1,2,3,4,4,5,6,7]

  oPolygon = obj_new('my_polygon', xy, LINESTYLE=5, POLYGONS=conn, STYLE=1)

end

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