Image Indices

Note: AVIRIS file “Lakes” is used as an example.

Features:

• Applies established indices to the dataset.

• Saves the new indices.

• Combines established and new indices in a pseudo color image, generating a composite index.

Steps:

1.      After opening a file, from the Main Interface, select Toolboxes → Image Indices → Vegetation Indices → AVIRIS.

A new window toolbox will appear.

The toolbox interface has four panels:

1. IMAGE DISPLAY panel shows a 2D image after applying the index. By default, it shows a Random Wavelength Index, which is simply a slice of a datacube at a randomly selected band/channel. Other standard indices are given in the following table.

2. STANDARD INDEX panel presents a selection of the established standard indices. Selection of the index from the dropdown menu and clicking Display Output updates the image on the Image Display panel.

3. CUSTOM INDEX panel allows you to develop your own index. Currently, IDCube supports two- and three-channel indexes. You can select the available channels from the dropdown menu and visualize the result on the IMAGE DISPLAY panel by clicking Display Output located on this panel and press Save New Index. You can add the new index to the list of indexes in the COMPOSITE INDEX panel (see below). The panel also allows to open a stored index via the Upload Index button.

4. COMPOSITE INDEX panel allows you to combine images generated by up to three individual indices into a pseudo RGB image. This panel has three subpanels. The sliders under the individual subpanels reflect the color of the channel: left slider – contributes to the red channel, middle slider – to the green channel, right slider – to the blue channel. The sliders also help the user to adjust the image prior to sending to the Image display. Each slider has to sub-sliders that can be moved.

Note: To be combined in the RGB image, each index image in the subpanel is normalized to [0, 1].

Index Image Display panel

The panel allows you to visualize established and newly developed indices as monochromatic images and composite indices in the RGB format. Each index comes with its own colormap. Some of the colormaps are specifically designed by IDCubePro® team for the corresponding indices. Other colormaps such as preset colormaps from the Color Toolbar or from the Right-click menu on the colorbar can be also applied. 

Standard Index panel

Steps:

1.      Select an option from the dropdown menu. There are currently 23 indices in our AVIRIS, AVIRIS-NG, and Hyperion index databases. Each index is made of two or three wavelengths. Wavelength selection for the same index differs across platforms because of differences in the hyperspectral hardware.

2.      The information about the index will be automatically shown in the ABOUT THE INDEX subpanel. The image corresponding to the selected index will be shown in the IMAGE DISPLAY panel.

3.      Click Display Output to visualize the index image

Custom Index panel

Steps:

1.      Activate the panel by Selecting Custom Indices radiobutton.

2.     Select the number of variables. Current choices:

a.      Two variables: allows to enter two bands.

b.      Three variables: allows to enter three bands.

3.      Type a formula (See Appendix 1 on notation and selections of available functions).

4.      Visualize the result on the INDEX IMAGE DISPLAY panel by clicking Display Output located on this panel.

5.      Save the index by clicking the Save New Index button.

(Optional). You can add a new index to the list of indices in the COMPOSITE INDEX panel by checking Add to the Composite Index box. A new index called custom1 will appear at the bottom of the list of indices in the COMPOSITE INDEX panel.

6.      You can also open a previously stored index via the Upload Index button.

Composite Index panel

Steps:

1.      There are three subpanels. Select an index from the dropdown menu on each of the subpanels. The index images will be immediately shown as monochromatic images. Pixel intensities on the image are normalized between 0 and 1 values.

2.      Use sliders to adjust the visual appearance of the image. Each slider box has two small sliders. To move the small slider, click on it to activate (changes the color from grey to color) and then use the left and right boxes to move the slider. Repeat the procedure to the second slider.       

3.      Repeat the steps on all three subpanels.

4.      Check View on Image Display to combine the index images together and visualize them on the INDEX IMAGE DISPLAY panel by pressing Combine as RGB on Image Display button. You can continue adjusting the subpanels with sliders. After every adjustment, click Combine as RGB to visualize on the INDEX IMAGE DISPLAY panel.

References:

The design of the sliders was based on the work by Danielle Ripsman, (2022). superSlider https://www.mathworks.com/matlabcentral/fileexchange/43285-superslider), MATLAB Central File Exchange. Retrieved May 11, 2022.