ETM+ Water Mask
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Click on the image for a larger view.
Press the "Del" key on the keyboard, and the water should completely vanish filled in by pure white.
Make sure the new foreground color is pure black again with the color selector by clicking on the "foreground color".
Set the RGB values to "R: 0", "G: 0", "B: 0". Then press the "OK" button as before to complete the color selection process.
Again click the little swap arrow between the "foreground color" and the "background color". This should move the pure black to the "background color" and the pure white to the "foreground color". You can see in the image below that I have already done this.
Navigate the menu control "Select->Inverse" or simply press "Shift Ctrl I" on the keyboard to invert the selection from water to land.
Press "Del" on the keyboard. The land should now vanish and be filled in by black land as shown in the image below.
Click on the image for a larger view.
Navigate the menu control "Image->Adjustments->Threshold...".
Adjust the "Threshold" slider as shown in the image below. The shoreline and lakes will expand or retreat as the slider is adjusted. You may see some noise on the slider spectrum. Try to find the optimal value. You can see here I have already found the optimum value, but it will most certainly be different for different images. The best value for the image you are working on will most likely be in a similar range to what I have selected in the image below.
Click the "OK" button to complete the "Threshold" adjustment.
Click on the image for a larger view.
Navigate the menu control again "File->Save As..."
Navigate your hard drive to find the appropriate place to save the file. Make sure the file name has the appropriate "Path###Row###" designation and add the label "WaterMask" to the end of the file name.
Make sure the format is set to ".bmp".
Click the "OK" button to finish the save operation. Adjust the "BMP Options" in the popup dialog box and again click the "OK" button.
Click on the image for a larger view.
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