Bio-Rad EXQuest Spot Cutter - Manual (Page 115)

PDQuest User Guide
3-36
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 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.
3.15.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 > Filters > Filter List. The pulldown menu includes all the filters
available in the Discovery Series.
The types of filters in the Discovery Series are:
• Weighted Mean. This filter is useful for reducing Gaussian noise; it has little
effect on salt and pepper. 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.
• Median. Also useful for suppressing salt and pepper noise, this filter has little
effect on Gaussian noise. It calculates the median value of the pixels within the
filtering window and uses it to replace the value of the pixel being processed. The
median filter produces very little blurring if a small-sized window is selected.
• Maximum. This filter is useful for eliminating pepper noise in an image (it
worsens the effect of salt noise). It replaces the value of the pixel being processed
with the maximum value of the pixels within the filtering window.
• Minimum. This filter replaces the value of the pixel being processed with the
minimum pixel value within the filtering window. This filter is useful for
eliminating salt noise in an image (it worsens the effect of pepper).