3. Working toolbar

_images/toolbar.jpg

Working toolbar

The Working toolbar allows for creating temporary ROIs and classification previews.

The functions are described in detail in the following paragraphs.

3.1. Image control

  • plugin: show the Main Interface Window;
  • zoom_to_Image: zoom the map to the extent of the active band set in Band set;
  • radiobutton RGB= input_list project_save: use the button to show/hide the active band set in Band set in the map; from the list select a Color Composite that is applied to the Band set; new color composites can be entered typing the band numbers separated by - or ; or , (e.g. RGB = 4-3-2 or RGB = 4;3;2 or RGB = 4,3,2);
  • cumulative_stretch: display the input image stretching the minimum and maximum values according to cumulative count of current map extent;
  • std_dev_stretch: display the input image stretching the minimum and maximum values according to standard deviation of current map extent;

3.2. Temporary ROI

A temporary ROI is a temporary polygon displayed in the map, which can be saved permanently in the Training input. A temporary ROI can be drawn manually or using a Region Growing Algorithm (i.e. the image is segmented around a pixel seed including spectrally homogeneous pixels).

  • zoom_to_ROI: zoom the map to the extent of temporary ROI;
  • radiobutton ROI: use the button to show/hide the temporary ROI and the Training input in the map;
  • manual_ROI: activate the pointer to create a temporary ROI by drawing a polygon in the map; left click on the map to define the ROI vertices and right click to define the last vertex closing the polygon; press the keyboard button CTRL to add a multipart polygon; press the keyboard buttons CTRL + Z for removing the last multipart polygon;
  • roi_single: activate the pointer to create a temporary ROI using the region growing algorithm; left click on the map for creating the ROI; right click on the map for displaying the spectral signature of a pixel of the active band set in the Spectral Signature Plot; press the keyboard button CTRL and left click to add a multipart polygon (new parts are not created if overlapping to other parts); press the keyboard buttons CTRL + Z for removing the last multipart polygon; press the keyboard button CTRL and right click to plot spectral signatures of the same pixel for all the band sets;
  • roi_redo: create a temporary ROI using the region growing algorithm at the same seed pixel as the previous one; it is useful after changing the region growing parameters;
Region growing parameters: the following parameters are required for the ROI creation using a region growing algorithm on the Band set:
  • Dist input_number project_save: set the interval which defines the maximum spectral distance between the seed pixel and the surrounding pixels (in radiometry unit);
  • Min input_number project_save: set the minimum area of a ROI (in pixel unit); this setting overrides the Range radius until the minimum ROI size is reached; if Rapid ROI on band is checked, then ROI will have at least the size defined Min ROI size; if Rapid ROI on band is unchecked, then ROI could have a size smaller than Min ROI size;
  • Max input_number project_save: set the maximum width of a ROI (i.e. the side length of a square, centred at the seed pixel, which inscribes the ROI) in pixel unit;

3.3. Classification preview

Classification preview allows for displaying temporary classifications (i.e. classification previews). Classification previews are useful for testing the algorithm in a small area of the Band set, before classifying the entire image which can be time consuming (see Classification output).

Classification preview is performed according to the parameters defined in Algorithm.

In addition to the classification raster, an Algorithm raster can be displayed, which is useful for assessing the distance of a pixel classified as class X from the corresponding spectral signature X. In Classification previews, black pixels are distant from the corresponding spectral signature (i.e. probably a new ROI, or spectral signature, should be collected in that area) and white pixels are closer to the corresponding spectral signature (i.e. probably the spectral signature identifies correctly those pixels).

After the creation of a new preview, old previews are placed in QGIS Layers inside a layer group named Class_temp_group (custom name can be defined in Temporary group name) and are deleted when the QGIS session is closed.

WARNING: Classification previews are automatically deleted from disk when the QGIS session is closed; a QGIS message (that can be ignored) could ask for the path of missing layers when opening a previously saved project.
  • zoom_to_preview: zoom the map to the extent of the last Classification preview;
  • radiobutton Preview: use the button to show/hide the last Classification preview in the map;
  • preview: activate the pointer for the creation of a Classification preview; left click the map to start the classification process and display the classification preview; right click to start the classification process and show the Algorithm raster of the preview;
  • preview_redo: create a new Classification preview centred at the same pixel as the previous one;
  • T input_number: change dynamically the classification preview transparency, which is useful for comparing the classification to other layers;
  • S input_number project_save: size of the preview in pixel unit (i.e. the side length of a square, centred at the clicked pixel);
  • remove_temp: remove from QGIS the classification previews that are archived in the Class_temp_group;