Description of Formulas - Image Filters (Beta)

The following describes each formula included in the Image Filter Formulas section of McIDAS-V.

Clean Image Filter
Cloud Image Filter
Core Image Filter
Discriminate Image Filter
Gradient Image Filter
High Pass 2D Image Filter
High Pass Image Filter
Hole Image Filter
Low Pass 2D Image Filter
Low Pass Image Filter
Merge Image Filter
Replace Image Filter
Shot Image Filter

Clean Image Filter (fill, bline, eline, pdiff, ldiff)

This formula cleans an image by first applying a shot noise filter to each element in the source region, and then locating and replacing bad lines. Each element is compared to the elements on either side and replaced if the values are significantly different. The average value of each line is then compared to the lines above and below and replaced if it is significantly different.

Input Parameter	Definition
fill	'Average': average of surrounding values (default) 'Min' : source dataset minimum value 'Max' : source dataset maximum value
bline	The beginning line in the source image region (default=first line).
eline	The ending line in the source image region (default=last line).
pdiff	The maximum percentage of the product range to allow before a new value for the pixel is derived using the average of two adjacent pixels (default=15).
ldiff	The minimum percentage of the product range to allow before a new value for the pixel is derived using the average of two adjacent pixels (default=15).
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).

Cloud Image Filter (replace, constant)

This formula applies a cloud filter to an image by comparing each element to the elements of another image. Use this filter to mask off a portion of the first source image.

Input Parameter	Definition
replace	The replacement value (default=minimum value in either sdataset)
constant	The additive constant (default=0)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=255).

Core Image Filter (brkpoint1, brkpoint2, replace1, replace2)

This formula applies a core filter to two images by comparing elements to breakpoints. The resulting image has only two values.

Input Parameter	Definition
brkpoint1	sdataset1 breakpoint value (default=minimum value in either source dataset)
brkpoint2	sdataset2 breakpoint value (default=maximum value in either source dataset)
replace1	success condition replacement value (default=maximum value in either source dataset)
replace2	failure condition replacement value (default=minimum value in either source dataset)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	if (sdataset1 > brkpoint1) and (sdataset2 > brkpoint2) then ddataset = replace1 else ddataset = replace2

Discriminate Image Filter (brkpoint1, brkpoint2, brkpoint3, brkpoint4, replace)

This formula applies a discriminate filter to two images by comparing elements in each image to different high and low breakpoints. Use this filter to mask off a portion of the first source image.

Input Parameter	Definition
brkpoint1	The low end breakpoint value for sdataset1 (default=minimum value in either source dataset)
brkpoint2	The high end breakpoint value for sdataset1 (default=maximum value in either source dataset)
brkpoint3	The low end breakpoint value for sdataset2 (default=minimum value in either sdataset)
brkpoint4	The high end breakpoint value for sdataset2 (default=maximum value in either sdataset)
replace	The replacement value (default=minimum value in either sdataset)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	if (brkpoint1 < sdataset1 < brkpoint2) and (brkpoint3 < sdataset2 < brkpoint2) then ddataset = sdataset1 else ddataset = replace

Gradient Image Filter

This formula applies a gradient filter to the source image.

Input Parameter	Definition
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
	ddataset = ABSOLUTE(sdataset_n - (sdataset_n+1) )

High Pass 2D Image Filter

This formula applies a two-dimensional high-pass filter to each element in the source image. It eliminates low-frequency deviations by clustering them around the distribution's midpoint. A sample average is calculated by the program using values in a two-dimensional region around the source element.

Input Parameter	Definition
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
	ddataset = (sdataset - (sample average ) + (sample midpoint))

High Pass Image Filter (radius, leak)

This formula applies a one-dimensional high-pass filter to each element in the source image. It eliminates low-frequency deviations by clustering them around the distribution's midpoint. A sample average is determined using values on either side of the source element and the percentage of filter efficiency.

Input Parameter	Definition
radius	The sample length surrounding the source element; used for sample average (default=50)
leak	The filter efficiency (default=100)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	ddataset = (sdataset - (sample average) + (sample midpoint) )

Hole Image Filter (brkpoint1, brkpoint2)

This formula searches for missing data and fills the holes in the image using the average of the surrounding element values.

Input Parameter	Definition
brkpoint1	The low end breakpoint value (default=minimum sdataset value)
brkpoint2	The high end breakpoint value (default=maximum sdataset value)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	if (brkpoint1 < sdataset < brkpoint2) then ddataset = (average of the surrounding sdataset element values) else ddataset = sdataset

Low Pass 2D Image Filter (linecoef, elecoef)

This formula applies a two-dimensional low-pass filter to each element in the source image. It eliminates high-frequency deviations by replacing the source image data values with the average of the values in the sample defined with the line and element coefficients.

Input Parameter	Definition
linecoef	The line coefficient; 0.0 < linecoef < 1.0 (default=0.5)
elecoef	The element coefficient; 0.0 < elecoef < 1.0 (default=linecoef)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	ddataset = (sample average)

Low Pass Image Filter (radius, leak)

This formula applies a one-dimensional low-pass filter to each element of the source image. It eliminates high-frequency deviations by replacing the source image data values with the average of the values on either side of the source element. The sample average is determined using the percentage of filter efficiency.

Input Parameter	Definition
radius	The sample length in pixels surrounding the source element; used for sample average (default=50)
leak	The filter efficiency (default=100)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	ddataset = (sample average)

Merge Image Filter (brkpoint1, brkpoint2, constant)

This formula merges two images by selecting the sdataset1 value for each element if its value is between the specified breakpoints. Otherwise, it selects the sdataset2 value minus the specified constant.

Input Parameter Definition

brkpoint1

The low end breakpoint value (default=minimum sdataset value)

brkpoint2

The high end breakpoint value (default=maximum sdataset value)

constant

The subtractive constant (default=0)

stretch

The stretch applied to the data, either Histogram or Contrast (default=Histogram).

BT Min

The minimum brightness value for calibration (default=0).

BT Max

The maximum brightness value for calibration (default=100).

Replace Image Filter (New Value, Old Value)

This formula replaces selected elements in the defined region of the source image with the specified replacement value.

Input Parameter	Definition
New Value	The replacement value (default=0)
Old Value	The source image values in the region to replace with outval; specify values in the list format, e.g., val1 val2 val3 etc., and/or a range format, e.g., bval-eval (default=0-255).
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	if sdataset lies outside the region defined by the line and element ranges then ddataset = sdataset else ddataset = replaceVal

Shot Image Filter (bline, eline, pdiff)

This formula cleans an image by applying a shot noise filter to each element in the source image. Each element is compared to the elements on either side and replaced if the values are significantly different.

Input Parameter	Definition
bline	The beginning line in the source image to clean (default=first line)
eline	The ending line in the source image to clean (default=last line)
pdiff	The maximum percentage of the product range to allow before a new value for the pixel is derived using the average of two adjacent pixels (default=15)
stretch	The stretch applied to the data, either Histogram or Contrast (default=Histogram).
BT Min	The minimum brightness value for calibration (default=0).
BT Max	The maximum brightness value for calibration (default=100).
Equation for each ddataset element:	if the difference between sdataset and the surrounding elements is < pdiff then ddataset = sdataset else ddataset = (average of the surrounding sdataset element values)

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