Density Slicing

Density slicing in NIH Image gives you the ability to highlight a range of pixel values in the LUT (Look Up Table) in the image you are currently working on. Pixel values range from 0 (absolute white) to 255 (absolute black). To turn on density slicing, follow this procedure:

Click on Options on the menu bar
Click on Density Slice. The color red will appear in place of some of the pixel values in the LUT.
Click on the density slicing tool
Place the cursor in the red area in the LUT.
Click and hold the mouse while sliding this tool up and down the LUT.
To turn off density slicing just re-click the Density Slice menu on the Options Menu Bar.

Download and open the Florida (image.tif.sit) (if not done in a previous activity) image in the NIH Program (clicking the image in Netscape will not open the program in NIH.) Using the above procedure observe how the gray scale pixels are replaced by red. One other observation of note is to look at the info window. Notice how the upper and lower values change as the density slice is moved up and down the LET. These are the all encompassing gray scale values being replaced by the density slice. They are the same ones in the image. If you place the density tool at a point just above or below the red slice, click and hold the mouse, you will stretch or squeeze the slice into a larger or narrower band of red. This will also increase or decrease the number of pixel values highlighted in the image.

Having the ability to vary the range of highlighted pixels in a density slice is extremely important. The procedure will allow measurements of specific parts of an image. Produce a density slice of thirty (30) pixels wide. Pull the slice so it highlights the pixels between 222 and 252.. What major geographical feature is highlighted in Red. Using a technique known as particle analysis, one can determine the area of Lake Okeechobee or the area of any other geographical feature with more precision than was demonstrated earlier. This technique will be demonstrated in the tutorial about density calibration.


	Hurricane Opal Project Activity These Links Are To Tutorial Activities Remote Sensing / Digital Numbers / Contrast / Brightness / Histograms / Measuring / Density Slicing / Particle Analysis / Density Calibration / DEMs / Elevation Calibration / Animation / Tutorial Site Map Email: proof@proofofconcepts.com Density Slicing You may print these instructions before starting this activity. Density slicing in NIH Image gives you the ability to highlight a range of pixel values in the LUT (Look Up Table) in the image you are currently working on. Pixel values range from 0 (absolute white) to 255 (absolute black). To turn on density slicing, follow this procedure: Click on Options on the menu bar Click on Density Slice. The color red will appear in place of some of the pixel values in the LUT. Click on the density slicing tool Place the cursor in the red area in the LUT. Click and hold the mouse while sliding this tool up and down the LUT. To turn off density slicing just re-click the Density Slice menu on the Options Menu Bar. Download and open the Florida (image.tif.sit) (if not done in a previous activity) image in the NIH Program (clicking the image in Netscape will not open the program in NIH.) Using the above procedure observe how the gray scale pixels are replaced by red. One other observation of note is to look at the info window. Notice how the upper and lower values change as the density slice is moved up and down the LET. These are the all encompassing gray scale values being replaced by the density slice. They are the same ones in the image. If you place the density tool at a point just above or below the red slice, click and hold the mouse, you will stretch or squeeze the slice into a larger or narrower band of red. This will also increase or decrease the number of pixel values highlighted in the image. Having the ability to vary the range of highlighted pixels in a density slice is extremely important. The procedure will allow measurements of specific parts of an image. Produce a density slice of thirty (30) pixels wide. Pull the slice so it highlights the pixels between 222 and 252.. What major geographical feature is highlighted in Red. Using a technique known as particle analysis, one can determine the area of Lake Okeechobee or the area of any other geographical feature with more precision than was demonstrated earlier. This technique will be demonstrated in the tutorial about density calibration. Hurricane Opal Project Activity Remote Sensing / Digital Numbers / Contrast / Brightness / Histograms / Measuring / Density Slicing / Particle Analysis / Density Calibration / Dams / Elevation Calibration / Animation / Tutorial Site Map Email: proof@proofofconcepts.com