How can I detect line lies between two certain regions?

I have matrix I and I want to detect and coloring the line ( or thin region) which has DN (4) and located between the region which has DN (0) and the region which has DN (3).

I =

0 0 0 0 4 4 3 3

0 0 0 4 4 3 3 2

0 0 4 4 3 2 2 2

0 4 4 3 3 2 2 3

Answer 1

[Image Analyst]

Simply use

coloredLabels = label2rgb (I, 'hsv', 'k', 'shuffle'); % pseudo random color labels

Here is a full demo:

I =[...
	0   0   0   0   4   4  3  3
	0   0   0   4   4   3  3  2
	0   0   4   4   3   2  2  2
	0   4   4   3   3   2  2  3]
hFig = figure;
subplot(2, 1, 1);
imshow(I, [], 'InitialMagnification', 1600);
fontSize = 16;
title('I', 'FontSize', fontSize);
% colorize the matrix
coloredLabels = label2rgb (I, 'hsv', 'k', 'shuffle'); % pseudo random color labels
% coloredLabels is an RGB image.  We could have applied a colormap instead.
subplot(2, 1, 2);
imshow(coloredLabels, 'InitialMagnification', 1600);
axis('on', 'image'); % Make sure image is not artificially stretched because of screen's aspect ratio.
title('Colorized I', 'FontSize', fontSize);
hp = impixelinfo; % Show color as use mouses around over image.

[faten Ahmed]

Thank you, but I want to detect and coloring the line (or thin region) which have DN (4) only.

[Image Analyst]

Try using rgb2ind() to apply a color map that maps each value into a color you specify:

I =[...
	0   0   0   0   4   4  3  3
	0   0   0   4   4   3  3  2
	0   0   4   4   3   2  2  2
	0   4   4   3   3   2  2  3]
hFig = figure;
subplot(2, 1, 1);
imshow(I, [], 'InitialMagnification', 1600);
fontSize = 16;
title('I', 'FontSize', fontSize);
customColorMap = [0,0,0; 0,0,0; 0,0,0; 1,0,0]
% colorize the matrix
coloredLabels = ind2rgb(I, customColorMap);
% coloredLabels is an RGB image.  We could have applied a colormap instead.
subplot(2, 1, 2);
imshow(coloredLabels, 'InitialMagnification', 1600);
axis('on', 'image'); % Make sure image is not artificially stretched because of screen's aspect ratio.
title('Colorized I', 'FontSize', fontSize);
hp = impixelinfo; % Show color as use mouses around over image.
drawnow;

[faten Ahmed]

the previous image is the result, Thank you. But, I want the line only between the building roof (DN 3) and the black region (DN 0, it is the shadow of the building)

Note that, there are many lines have DN=4, but I wnat to detect the lines beside black region only.

[Image Analyst]

Take the 3 region and the 0 region and dilate one of them and then AND them. Something like (untested)

region3 = imdilate(labeledImage == 3, true(3));
borderImage = region3 & (labeledImage == 0);
imshow(borderImage, []);

Answer 2

[darova]

• imbinarize image
• use bwareaopen to clear a bit
• use edge