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.

marker = false(size(mask));
marker(65:70,65:70) = true;

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.

J = mask;
J(marker) = 255;
figure
imshow(J)
title('Marker Image Superimposed on Mask')

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')