Image histograms and index can be displayed simultaneously with the image and a tool 
box provides real-time pan and zoom as well as control point and training area selection 
(Figure 3). 
Selection Tool 
Zoom Tool 
Control Point Editor 
Spectral Point Samper 
* 
m 
mmm 
i i 
O 
Pan Tool 
Training Area Editor 
Spectral Area Sampler 
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Lilli,! 
Figure 3: Dirigo tool box. 
Image Data Management 
Based on our experiences in remote sensing and the display size of the Macintosh-II, we 
designed the image management system to handle files of 512 x 512 pixels. The 
number of bands is limited only by disk space. However, the user can only select three 
bands for display and interactive manipulation (Figure 4). Band description (e.g., 
spectral information) can be stored in the header and is provided to the user when an 
image file is opened. The Dirigo system supports four different file formats: (1) image 
data; (2) ASCII text files (control point coordinates or training area statistics); (3) 
classified images; and (4) training areas for classification. Intelligent interface design 
ensures that only files with the appropriate format can be opened for the selected 
application tasks. 
Figure 4: After opening an image file (here Marsh Island), the header information is 
made available to the user. The user can then select three bands for display. 
Image Display 
Dirigo provides color display for up to three eight-bit input channel. The user can select 
three spectral bands from an input image by assigning red, green and blue color squares