Main OpenEV Window

The main OpenEV display window contains the geospatial data viewing area, as well as menus and an iconbar. The button and key sequences for manipulating view state are decribed in the separate View Area Button/Key Sequences page.

The area at the bottom of the view window is the track tool and display position and raster value under the cursor. Details preferences for controlling the tracking tool are available in the application preferences panel (Edit->Preferences).

Icon Bar

Open File: Open a raster or vector file, and add to this view. Same as File->Open.

Print: Launch the Printing Dialog to print the current view.

Remove Enhancement: Remove any greyscale enhancement lut (such as applied by the equalize icon) from the active raster layer. Does nothing if no raster layer is selected in the layers dialog. Note that a linear scaling stretch will still be in effect for non-eight bit data.

Linear Enhancement: Perform a linear stretch enhancement.

Histogram Equalization: Apply a histogram equalization enhancement LUT to the active raster. This is a non-linear constrast stretch intended to flatten out the post-enhancement histogram. See the GvRasterLayer::equalize() method in pymod/ for details on the algorithm used. Does nothing if a raster layer is not selected in the layers dialog.

Logarithmic Enhancement: Perform a logarithmic stretch enhancement. The enhancment lut is recomputed to map the minimum to zero, the maximum to 255 and intermediate values based on logarithmic scaling. See GvRasterLayer::log() for algorithmic details.

Windowed Raster Re-enhancement: Recompute the last enhancement (linear, equalize, logarithmic) based on pixels currently visible in the view. The scaling min/max and enhancement are recomputed. In 3D mode substantial numbers of pixels not actually visible in the view may be included in the calculation.

Classify Raster: Launches a dialog for applying a pseudo-color classification to a single raster band. This is a GIS style classification, not a multispectral classification. The dialog can only be launched if a raster layer is selected. The dialog is not currently further documented.

Show Legend: Launches a dialog displaying the current classification legend generated by the Classify Raster dialog. If there is no classification in force on the current raster, or if no raster layer is selected nothing will happen.

Fit all Layers: Resets the view position, and zoom level such that all the data in all view layers is shown. As currently implemented the any rotation is lost.

Zoom Control: Displays the zoom level of the currently selected raster layer. A value of 1:2 would indicate decimation by 2, while 2:1 would indicate duplication of raw pixels by a factor of two. The user can selected a desired zoom level from popup menu, or directly type in zoom ratios. The control has no effect when a non-raster layer is selected.

Zoom In: Zoom in (making features bigger) by a factor of 2.
Zoom Out: Zoom out (making features larger) by a factor of 2.
Refresh Raster from Disk: Causes the current raster layer to be reloaded from disk, or from it's source Numeric Python array. There are various levels of caching applied in OpenEV, and data is normally only re-read from disk when not available in memory. If a file is updated on disk (or a display numerical python array is updated) the refresh function can be used to force the display to be resyncronized from the source data. Applies to the active raster layer. If no raster layer is active nothing happens.

Georeferenced Display: When the black and white icon is visible, the view is being displayed in raw pixel/line coordinates for the source raster. When the color icon is displayed the view is trying to display in georeferenced units (if any are available). Selecting this icon will toggle the state. This icon is generally used to switch between raw and warped images for images that include control points that will define a polynomial warp (such as many CEOS images). The initial state of this icon is determined by the "Display Georeferenced" control on the Raster tab of the Preferences dialog.

Online Help: Launch the OpenEV online help, the same as Help->Help.

Online Help: Launch the OpenEV online help, the same as Help->Help.

Busy/Idle Indicator: The red icon shows when the application is busy, and the green icon displays when the application is idle. Due to the background loading of data the application will often be busy for a short time after initially displaying a raster. Pressing the icon has no effect, and even when the application is busy it should remain responsive if somewhat more sluggish than when idle.



Import raster for optimized access. The user is prompted to select a raster data file. This is converted into tiled GeoTIFF format in the current working directory, overview levels are built, and the imported file is added to the current view (as if it had been opened).

The imported file is optimized for fast access, but may lose some information from the source file (such as metadata). Note that vector files cannot be imported.

Open a raster or vector file, and add it to the current view as a new layer. For files with a greater than eight bit data type, min/max values will be computed for scaling purposes. The resulting layer will be assigned the name of the source file.

Open 3D
Brings up a dialog for selection of a drape and elevation raster. They are added to the current view as a 3D image, and the view is placed in 3D mode.

Save Vector Layer
Brings up a file selector for entry of a filename to save the active vector layer to. The file saved to will be in ESRI Shapefile format. ESRI Shapefiles can only support one type of geometry per file (point, line, area) so if the active layer has a mixture, only one of the types (the first encountered) will be saved. Feature attributes are only saved if they are described by a schema on the layer, as is the case with vectors loaded from a shapefile.

New View
Creates a new OpenEV view window with an independent set of data layers, and makes it the current view.

Launches the Printing Dialog for printing the view contents.

Recent Filenames
A list of recently opened files is maintained in this menu. Selecting one is equivelent to doing a File->Open, and entering the displayed name.

Close the current window. If this is the last main display window for this OpenEV process the user is prompted if they want to exit the whole process.

Close all windows, and terminate OpenEV. The user is prompted for confirmation.


Undoes the last undoable operation. Currently only the various vector editing operations are undoable. View changes, layer property changes and addition or deletion of layers are not undable. The undo stack is not bounded, and so in theory many undo steps are available; however, certain operations, like destruction of undoable layers results in clearing of the entire undo stack.

Launches the Layer Management Dialog for manipulating view layers.

Vector Layer Attributes...
Launches the vector features attributes dialog for inspecting, and changing the attributes of the selected feature.

Edit Toolbar...
Launches the Edit Tools for controlling editing mode.

Go To...
Launches a simple dialog for recentering the view around a particular georeferenced location.

Python Shell...
Launches a Python Shell. This is a dialog for interactively entering Python commands for simple image processing and other scripting needs.

3D Position...
Launches a dialog for setting the 3D view position and direction.

Launches the application preferences panel for viewing, and modifying application wide preferences.

Python Shell...
Launches the python shell for doing numerical python operations.

3D Position...
Launches the 3D position dialog for viewing, and modifying the 3D view position.


Note that online help is displayed as HTML files, and OpenEV needs access to an HTML viewing application. On Windows the default system HTML viewer is used. On Unix various well known browsers are searched for (ie. netscape, Mosaic). The user can customize this in the application preferences panel available under Edit->Preferences.

The help topic for most dialogs can be launched directly by hitting F1 after clicking on the dialog.

Displays application help.

Web Page
Displays the OpenEV web page.
Display OpenEV information, and credits.