Minimum/Maximum

std.Minimum(clip clip[, int[] planes=[0, 1, 2], float threshold, bint[] coordinates=[1, 1, 1, 1, 1, 1, 1, 1]])

Replaces each pixel with the smallest value in its 3x3 neighbourhood. This operation is also known as erosion.

clip
Clip to process. It must have integer sample type, and bit depth between 8 and 16. If there are any frames with float samples or bit depth greater than 16, an error will be returned.
planes
Specifies which planes will be processed. Any unprocessed planes will be simply copied.
threshold
Allows to limit how much pixels are changed. Output pixels will not become less than input - threshold. The default is no limit.
coordinates

Specifies which pixels from the 3x3 neighbourhood are considered. If an element of this array is 0, the corresponding pixel is not considered when finding the minimum value. This must contain exactly 8 numbers.

Here is how each number corresponds to a pixel in the 3x3 neighbourhood:

1 2 3
4   5
6 7 8
std.Maximum(clip clip[, int[] planes=[0, 1, 2], int threshold=65535, int[] coordinates=[1, 1, 1, 1, 1, 1, 1, 1]])

Replaces each pixel with the largest value in its 3x3 neighbourhood. This operation is also known as dilation.

clip
Clip to process. It must have integer sample type, and bit depth between 8 and 16. If there are any frames with float samples or bit depth greater than 16, an error will be returned.
planes
Specifies which planes will be processed. Any unprocessed planes will be simply copied.
threshold
Allows to limit how much pixels are changed. Output pixels will not become greater than input + threshold. With the default value of 65535 there is no limit.
coordinates

Specifies which pixels from the 3x3 neighbourhood are considered. If an element of this array is 0, the corresponding pixel is not considered when finding the maximum value. This must contain exactly 8 numbers.

Here is how each number corresponds to a pixel in the 3x3 neighbourhood:

1 2 3
4   5
6 7 8