1- Right click on this image to download.
2- Download the AnalyzingDigitalImages software as part of the DEW software bundle from the software download page.
3- Double click the AnalyzingDigitalImages application. Use the 'Open a Picture' button in the upper left of the screen to load the jpeg file from step 1. It is Portland, Maine - ETM2000.jpg, from an Aug 26 2000 Landsat image.
4- You can define a scale or not. Say none for now. The unit of pixels will work since this jpeg was made from a 512 by 512 pixel data input. So the percent of the image that matches the user-defined box of 3-color bands could be computed in square meters if desired, since one Landsat TM or ETM+ pixel is 28.5 m on a side.
5- Now that you have the image on the screen, try this example:
To draw a rectangle in AnalyzingDigitalImages, click on the mouse for the upperleft corner of the area you want to highlight and drag the cursor. When you release the mouse button, the red dot is the lower right of your box.
A black and white image appears where black represents the pixels that match the range of RGB of those in the box. The white is the unmatched pixels. The number of masked pixels can be viewed in the 'Spatial Analysis' tab panel. To view the percentage of masked pixels, select 'Save Measurement' from the Measurement menu and follow the instructions to save your data. The percentage of masked pixels will appear in a window like the one below.
Now decide on what other color/landuse you may like to see. I suggest deep ocean, light pink areas, the cove area, bright blue in urban area, and grey-blue in urban area, and medium red. I noticed that the sum of all the "color types" did not add up to 100%.What landuse do you think these boxes represent -- e.g. lakes and rivers, etc ?