 |
Unsharp Masking
An unsharp mask effect can be produced in the computer by applying a Gaussian blur to a duplicate of the original and then subtracting it from the original. The difference between the two images is just the detail and edges removed by the blurring. The original image is then added back to the difference to increase the visibility of the details while suppressing the overall image contrast. This interactive tutorial illustrates unsharp masking to increase local contrast at steps and edges. In the tutorial, the result image is automatically scaled to the range of the display so that negative values that can result from the calculation are not lost.
The tutorial initializes with a randomly selected specimen appearing in the Specimen Image window. The Choose A Specimen pull-down menu provides a selection of specimen images, in addition to the initial randomly chosen one. The Standard Deviation slider adjusts the size of the Gaussian smoothing convolution used to create a blurred copy of the image, which is then subtracted from the original. The Amount to Add slider adjusts the percentage of the resulting difference that is added back to the original to produce the resulting Filtered Image shown on the right. For color images, the processing is applied only to the pixel brightness values, retaining the original color information.
Contributing Authors
John C. Russ - Materials Science and Engineering Dept., North Carolina State University, Raleigh, North Carolina, 27695.
Matthew Parry-Hill, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
BACK TO INTRODUCTION TO DIGITAL IMAGE PROCESSING AND ANALYSIS
BACK TO MICROSCOPY PRIMER HOME
Questions or comments? Send us an email.
© 1998-2009 by Michael W. Davidson, John Russ, Olympus America Inc., and The Florida State University. All Rights Reserved. No images, graphics, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders. Use of this website means you agree to all of the Legal Terms and Conditions set forth by the owners.
This website is maintained by our
Graphics & Web Programming Team
in collaboration with Optical Microscopy at the
National High Magnetic Field Laboratory.
Last modification: Tuesday, Sep 11, 2018 at 01:47 PM
Access Count Since July 20, 2006: 6161
For more information on microscope manufacturers,
use the buttons below to navigate to their websites:
