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Section 2 - Using PIPSpro
Three standard high pass filters are provided and the kernel values
are shown. For a frame of 3x3 these values will define the kernel. For
larger frames, the intervening pixels are set to zero.
If Non Linear is selected, there is a choice of a median filter or a
Kuwahara filter.
With the median filter the user may choose one of the following options:
Row Only (1-D filter will be applied to the image rows),
Column Only (1-D filter will be applied to the image columns),
Cross (2-D filter using pixels from the horizontal and vertical lines
through the current pixel),
Whole Area (full 2-D filter will be used).
The kernel size can be selected from the dialog window.
A custom sharpening filter mask can be entered using Edit Mask.
If the Frame is larger than 3x3 the intervening pixels will be set to
zero.
HINT: The median filter is a standard image processing technique,
particularly useful for removing “salt and pepper” noise from images
without reducing the fine details.
The Kuwahara filter is designed to reduce noise without degrading the
sharpness or position of edges.
The following image shows a test image from the QC-3 phantom, and
three different filtering operations using the average (3x3), median
(whole area 3x3) and Kuwahara (5) filters.
Click on ES to select an edge sharpening algorithm specially developed
for portal images. A suitable scaling factor should be selected (typically
in the range 1-3). For a description of this algorithm, see the ‘Sequential
image processing’ section of this manual.
Contrast
This provides several different contrast enhancement techniques. See
Tutorials 2-4.
Global Histogram Equalization equalizes the histogram of the whole
image. The dialog window allows the user to select a particular grey
scale interval for the histogram before and after equalization.
Sharpen Image
This provides the capability of high pass filtering with different weight
coefficients. The kernel size (Frame), scaling factor and shift of the
grey scale can be selected from the corresponding fields of the dialog
window.
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Local Histogram Equalization includes the following adaptive histogram equalization techniques: