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boundarymask

Find region boundaries of segmentation

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Syntax

mask = boundarymask(L)
mask = boundarymask(BW)
mask = boundarymask(___,conn)

Description

mask = boundarymask(L) computes a mask that represents the region boundaries for the input label matrix L. The output, mask, is a logical image that is true at boundary locations and false at non-boundary locations.

example

mask = boundarymask(BW) computes the region boundaries for the input binary image BW.

mask = boundarymask(___,conn) computes the region boundaries using a connectivity specified by conn.

Examples

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Open Live Script

Read an image into the workspace.

I = imread('kobi.png');

Create a superpixel representation of the image, returned as a label matrix.

L = superpixels(I,100);

Display the label matrix.

imshow(label2rgb(L))

Figure contains an axes object. The hidden axes object contains an object of type image.

Find the region boundaries of the label matrix.

mask = boundarymask(L);

Display the boundary mask over the original image by using the labeloverlay function. The region boundaries of the label matrix appear as 1-pixel wide cyan lines.

imshow(labeloverlay(I,mask,'Transparency',0))

Figure contains an axes object. The hidden axes object contains an object of type image.

Input Arguments

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Label matrix, specified as a 2-D numeric matrix of nonnegative numbers or a 2-D logical matrix.

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

Binary image, specified as a numeric or logical matrix of the same size as L.

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

Pixel connectivity, specified as 4 or 8.

Value

Meaning

Two-Dimensional Connectivities

4

Pixels are connected if their edges touch. The neighborhood of a pixel are the adjacent pixels in the horizontal or vertical direction.

3-by-3 pixel neighborhood with four pixels connected to the center pixel

Current pixel is shown in gray.

8

Pixels are connected if their edges or corners touch. The neighborhood of a pixel are the adjacent pixels in the horizontal, vertical, or diagonal direction.

3-by-3 pixel neighborhood with 8 pixels connected to the center pixel

Current pixel is shown in gray.

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

Output Arguments

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Rasterized grid of region boundaries, specified as a 2-D logical matrix of the same size as the input image. A pixel in mask is true when the corresponding pixel in the input image with value P has a neighboring pixel with a different value than P.

Data Types: logical

Extended Capabilities

Version History

Introduced in R2016a

See Also

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