Filter Image Filter Tool - Settings Tab

Defines the image enhancement technique that will be applied to the region.The result of the image enhancement technique will automatically update within the region.

Filter Type Description
Binarize (default)

Filters the image based on a greyscale threshold into white (255) or black (0); outputs an image where input pixel values equal to or above the threshold value are white, and values below the threshold are black.

Note: When a color input image is used, the output image will be a greyscale image.
Bottom Hat

Filters out everything except dark features smaller than the Filter Size; outputs an image that displays dark features as bright pixels on a dark background.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Clip

Filters the image by comparing the greyscale value of each individual pixel to a minimum and maximum greyscale value; outputs an image where the extreme ends of the greyscale spectrum are eliminated so features are more uniform.
Close

Filters out dark features smaller than the Filter Size; outputs an image with a slightly increased overall brightness level.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Dilate

Increases bright features and shrinks dark features; outputs an image with larger areas of light pixels. This filter is useful for removing dark spots or specks.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Edge Magnitude

Filters dark and light features; outputs an image where edges are represented as light pixels. This operation accounts for diagonally oriented edges, and is slower than the "Gradient Full" Operation.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Equalize Filters based on a histogram equalization, where the most frequent greyscale values are equalized to create a more even distribution; outputs an image with increased contrast.
Erode

Increases dark features and shrinks bright features; outputs an image larger areas of dark pixels. This filter is useful for removing light spots or specks.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Fill Dark Holes Dark pixels surrounded by light pixels are converted to light pixels; outputs an image where dark holes are filled.
Fill Light Holes Light pixels surrounded by dark pixels are converted to dark pixels; outputs an image where light holes are filled.
Gradient Full Filters vertical and horizontal edge features; outputs an image where vertically and horizontally oriented edges are represented by light pixels. This operation does not account for diagonally oriented edges, but is faster than the "Edge Magnitude" Operation.
Gradient Horizontal Filters horizontal edge features; outputs an image where horizontally oriented edges are represented by light pixels.
Gradient Vertical Filters vertical edge features; outputs an image where vertically oriented edges are represented by light pixels.
Greyscale Distance

Filters based on the greyscale value of each output pixel as the difference between the greyscale value of each input pixel and the threshold level; outputs an image where, for example, if the input pixel value is 100 and the threshold is 25, the output pixel value is 75.
High Pass

Filters edge features and suppresses other features; outputs an image where edges are enhanced relative to areas with a more consistent grayscale gradient.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Invert Filters based on a greyscale inversion of pixel values; outputs an image that is a "negative" of the input image.
Local Median

Specifies an operation that computes the median pixel value of the pixel values in the kernel neighborhood, then uses this result as the output image pixel value.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Local Median Normalization

Specifies a means to subtract the background from an image; this operation subtracts the local median of the input image from the input image, shifts the result right by one, and then adds 128 to produce the output pixel value.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Low Pass

Filters edge features and blurs the edge with other features; outputs an image where edges are "smoothed" or blurred.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Max (Top Hat/Bottom Hat)

Specifies an operation that uses the maximum of Top Hat and Bottom Hat operations.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Open

Filters out light features smaller than the Filter Size; outputs an image with a slightly decreased overall brightness level.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.
Optical Density

Filters based on an inversion of pixel values on a logarithmic scale; outputs an image that reveals the density of objects and features by measuring the amount of light passing through them. Denser objects and features are represented by lighter pixels in the output image.
Sharpen

Specifies a "sharpness" operation that is used to enhance edges. The operation evaluates the contrast between adjacent pixels, and increases the contrast when the contrast is high. A large contrast difference between adjacent pixels usually represents an edge; however, this operation should not be used to locate edges. The effects that the operation will have are dependent upon the image content and the resolution.

  • The Gain parameter dictates the strength of the sharpening, instructing the filter to ignore a certain amount of difference between pixels when sharpening so that lightly textured areas will not be over-sharpened.
Stretch Filters by linearly scaling or "stretching" the greyscale values; outputs an image with increased contrast.
Threshold Range

Filters based on a binary (black and white) threshold which compares each input pixel with two threshold values (minimum and maximum) to determine whether the output pixel is white or black; outputs an image where if the input pixel value is equal to or exceeds the minimum or maximum, the output pixel is white, and if the input pixel value is within the minimum or maximum, the output pixel is black.
Top Hat

Filters out everything except light features smaller than the Filter Size; outputs an image that displays light features as bright pixels on a dark background.

Note: This operation enables the Kernel Rows and Kernel Columns parameters. The kernel must be constructed from odd integer values.

Specifies the number of rows (1–25; default = 3) of the kernel. A kernel is a rectangular array of numbers that defines the processing neighborhood for operations performed on each pixel location of an image. The greyscale values of a pixel's neighbors defines the greyscale value for that pixel location in the output image.

Note:
  • The kernel is unweighted.
  • The kernel must be constructed from odd integer values. A typical kernel is 3 x 3, but the size is arbitrary.

This parameter is enabled when the Filter Type is set to one of the following:

  • Bottom Hat
  • Close
  • Dilate
  • Edge Magnitude
  • Erode
  • High Pass
  • Local Median
  • Local Median Normalization
  • Low Pass
  • Max (Top Hat/Bottom Hat)
  • Open
  • Top Hat

Specifies the number of columns (1–25; default = 3) of the kernel. A kernel is a rectangular array of numbers that defines the processing neighborhood for operations performed on each pixel location of an image. The greyscale values of a pixel's neighbors defines the greyscale value for that pixel location in the output image.

Note:
  • The kernel is unweighted.
  • The kernel must be constructed from odd integer values. A typical kernel is 3 x 3, but the size is arbitrary.

This parameter is enabled when the Filter Type is set to one of the following:

  • Bottom Hat
  • Close
  • Dilate
  • Edge Magnitude
  • Erode
  • High Pass
  • Local Median
  • Local Median Normalization
  • Low Pass
  • Max (Top Hat/Bottom Hat)
  • Open
  • Top Hat

Specifies whether or not the tool will automatically determine a threshold level when the Filter Type is set to Binarize, Greyscale Distance, or Threshold Range.

  • Manual: Enables the Threshold parameter and manually specify the threshold levels.
  • Auto (Default):
    • When the Filter Type is set to Binarize, the tool automatically computes a threshold level based on the greyscale values within the specified region.
    • When the Filter Type is set to Greyscale Distance, the tool will automatically compute a threshold value based on the mean greyscale value within the specified region.
    • When the Filter Type is set to Threshold Range, the following is automatically applied:
      • If the pixel values are less than the Min parameter setting, or the pixel values are greater than the Max parameter setting, the pixel values will be set to background.
      • If the pixel values are within the Min and Max parameter settings, the pixel values will be set to foreground.

Specifies the threshold levels (0 to 255; default = 128) when the Filter Type is set to Binarize, Greyscale Distance, or Threshold Range.

Specifies the minimum greyscale value (0–255; default = 128) when the Filter Type is set to Clip, Stretch or Threshold Range.

Specifies the maximum greyscale value (0–255; default = 128) when the Filter Type is set to Clip, Stretch or Threshold Range.

Specifies a gain value (0 to 10; default = 1) when the Filter Type is set to Sharpen.This parameter dictates the strength of the sharpening that will be performed by controlling the amount of edge contrast enhancement. Pixels around an edge are driven to their minimum or maximum values to create a sharper appearance of the edge.

Specifies the smoothness value (1 to 4; default = 1) for the Gaussian kernel when the Filter Type is set to Sharpen.Smoothness controls the standard deviation of the Gaussian kernel; higher smoothness values result in a wider "aperture" for the smoothing operation, helping to sharpen features.

Note: Gaussian refers to a bell-shaped curve that is applied as a weighted average to the pixels in the ROI.