Median Filters

The median filter functions perform non-linear filtering of a source image data.

These functions use either an arbitrary rectangular mask, or the following predefined masks of the IppiMaskSize type to filter an image:

ippMskSize3x1

Horizontal mask of length 3

ippMskSize5x1

Horizontal mask of length 5

ippMskSize1x3

Vertical mask of length 3

ippMskSize3x3

Square mask of size 3

ippMskSize1x5

Vertical mask of length 5

ippMskSize5x5

Square mask of size 5

The size of the neighborhood and coordinates of the anchor cell in the neighborhood depend on the mask mean. Table “Median Filter Mask, Neighborhood, and Anchor Cell” lists the mask types with the corresponding neighborhood sizes and anchor cell coordinates. Note that in mask names the mask size is indicated in (XY) order. The anchor cell is specified by its coordinates anchor.x and anchor.y in the coordinate system associated with the upper left corner of the mask.

Median Filter Mask, Neighborhood, and Anchor Cell

Mask

Neighborhood Size

Anchor Cell

Columns

Rows

ippMskSize3x1

3

1

[1, 0]

ippMskSize5x1

5

1

[2, 0]

ippMskSize1x3

1

3

[0, 1]

ippMskSize3x3

3

3

[1, 1]

ippMskSize1x5

1

5

[0, 2]

ippMskSize5x5

5

5

[2, 2]

Median filters have the effect of removing the isolated intensity spikes and can be used to achieve noise reduction in an image.

For details on algorithms used in Intel IPP for median filtering, see [APMF].


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