J = imimposemin(I,BW)
modifies the grayscale mask image I using morphological reconstruction
so it only has regional minima wherever binary marker image BW is
nonzero.
This example shows how to modify an image so that one area is always a regional minimum.
Read an image and display it. This image is called the mask image.
mask = imread('glass.png');
imshow(mask)
Create a binary image that is the same size as the mask image and sets a small area of the binary image to 1. These pixels define the location in the mask image where a regional minimum will be imposed. The resulting image is called the marker image.
Superimpose the marker over the mask to show where these pixels of interest fall on the original image. The small white square marks the spot. This code is not essential to the impose minima operation.
Impose the regional minimum on the input image using the imimposemin function. Note how all the dark areas of the original image, except the marked area, are lighter.
K = imimposemin(mask,marker);
figure
imshow(K)
To illustrate how this operation removes all minima in the original image except the imposed minimum, compare the regional minima in the original image with the regional minimum in the processed image. These calls to imregionalmin return binary images that specify the locations of all the regional minima in both images.
BW = imregionalmin(mask);
figure
subplot(1,2,1)
imshow(BW)
title('Regional Minima in Original Image')
BW2 = imregionalmin(K);
subplot(1,2,2)
imshow(BW2)
title('Regional Minima After Processing')
Binary marker image, specified as a numeric or logical array of the same size as the
grayscale mask image I. For numeric input,
any nonzero pixels are considered to be 1 (true).
Pixel connectivity, specified as one of the values in this table. The default
connectivity is 8 for 2-D images, and 26 for 3-D
images.
Value
Meaning
Two-Dimensional Connectivities
4-connected
Pixels are connected if their edges touch. The neighborhood of a pixel
are the adjacent pixels in the horizontal or vertical
direction.
8-connected
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.
Three-Dimensional Connectivities
6-connected
Pixels are connected if their faces touch. The neighborhood of a pixel
are the adjacent pixels in:
One of these directions: in, out, left, right, up, and
down
18-connected
Pixels are connected if their faces or edges touch. The neighborhood of
a pixel are the adjacent pixels in:
One of these directions: in, out, left, right, up, and
down
A combination of two directions, such as right-down or
in-up
26-connected
Pixels are connected if their faces, edges, or corners touch. The
neighborhood of a pixel are the adjacent pixels in:
One of these directions: in, out, left, right, up, and
down
A combination of two directions, such as right-down or
in-up
A combination of three directions, such as in-right-up or
in-left-down
For higher dimensions, imimposemin uses the default value
conndef(ndims(I),'maximal').
Connectivity can also be
defined in a more general way for any dimension by specifying a 3-by-3-by- ... -by-3 matrix of
0s and 1s. The 1-valued elements
define neighborhood locations relative to the center element of conn. Note
that conn must be symmetric about its center element. See Specifying Custom Connectivities for more information.
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