integralBoxFilter3

3-D box filtering of 3-D integral images

Syntax

B = integralBoxFilter3(A)

B = integralBoxFilter3(A,filterSize)

B = integralBoxFilter3(___,Name,Value)

Description

B = integralBoxFilter3(A) filters integral image A with a 3-by-3-by-3 box filter.

B = integralBoxFilter3(A,filterSize) filters integral image A with a 3-D box filter with size specified by filterSize.

B = integralBoxFilter3(___,Name,Value) uses name-value pairs to control various aspects of the filtering.

Examples

Filter 3-D MRI Volume with Box Filter

Load 3-D MRI data.

volData = load('mri');
vol = squeeze(volData.D);

Pad the image volume by the radius of the filter neighborhood.

filterSize = [5 5 3];
padSize = (filterSize-1)/2;
volPad = padarray(vol, padSize, 'replicate', 'both');

Calculate the 3-D integral image of the padded input.

intVol = integralImage3(volPad);

Filter the 3-D integral image with a [5 5 3] filter.

volFilt = integralBoxFilter3(intVol, filterSize);

Input Arguments

A — Integral image to be filtered

3-D numeric array

Integral image to be filtered, specified as a 3-D numeric array.

integralBoxFilter3 expects the input integral image, A, to be an upright integral image computed using integralImage3. integralBoxFilter3 does not support rotated integral images. The first row, column and plane of the integral image is assumed to be padded, as returned by integralImage3.

Data Types: double

filterSize — Size of box filter

3 (default) | positive, odd integer | 3-element vector of positive, odd integers

Size of box filter, specified as a positive odd integer or 3-element vector of positive, odd integers. If filterSize is scalar, then integralBoxFilter3 uses a cube box filter.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: B = integralBoxFilter3(A,5,'NormalizationFactor',1);

NormalizationFactor — Normalization factor applied to box filter

1/filterSize.^3, if scalar, and 1/prod(filterSize), if vector (default) | numeric scalar

Normalization factor applied to box filter, specified as a numeric scalar.

The default 'NormalizationFactor' has the effect of a mean filter—the pixels in the output image are the local means of the image. To get local area sums, set 'NormalizationFactor' to 1. To avoid overflow in such circumstances, consider using double precision images by converting the input image to class double.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Output Arguments

B — Filtered image

3-D numeric array

Filtered image, returned as a 3-D numeric array. integralBoxFilter3 returns only the parts of the filtering that are computed without padding.

Data Types: double

Version History

Introduced in R2015b