User guide

Quantity One User Guide
12-34
The available filter dimensions range from 3 x 3 pixels to 9 x 9 pixels. To select
an appropriate size, magnify a background region of your image so that you
can see the individual pixels. The filter size you select should be larger than
the average noise feature but smaller than your data features.
Note: A smaller filter will alter your image less than a larger filter. Large filters
can result in better suppression of noise, but can also blur desirable
features in the image.
Step 3: Begin Filtering
After you have completed your selections, the filter name and size will be
displayed at the bottom of the Filter Wizard dialog box.
To being filtering, click on the OK button. Because filtering is an irreversible
process, a pop-up box will give you the option of filtering the original image,
creating a copy of the image to filter, or cancelling out of this operation.
If you choose to Copy and Filter, you will be asked to enter a new name and/
or version number for the new copy before the operation is performed. Once
this information has been entered, the filtering operation will be performed.
12.10.b Selecting a Filter Directly
If you already know the type and size of filter you want, you can select it
directly by selecting Image > Filter List. The submenu includes all the
available filters.
The types of filters are:
• Weighted Mean. This filter is useful for reducing Gaussian noise. It
calculates the weighted mean of the pixels within the filtering window
and uses it to replace the value of the pixel being processed.
• Out of Range Pixel. This filter is useful for suppressing salt-and-pepper
noise; its effect on Gaussian noise is minimal. This filter calculates the
mean of the pixel values in the filtering window, including the pixel being
processed. If the difference between the mean and the individual pixel
value is above a certain threshold, then the individual value is replaced
by the mean.