Help with the measurement of cracks' width and lenght

Hello everyone,
I processed this image of a crack and I need to measure its lenght and width. About the lenght, I tried to use the skeleton plugin and I’m uploading the results so you can tell me where should I get from these the lenght, but I don’t know how to measure the width.
Can somebody help me?
The image I’m talking about it’s the one uploaded.
Thank you
Immagine 3a.tif (5.1 MB)
Branch information.pdf (81.2 KB)
Results.pdf (76.8 KB)

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There is a good explanation of @phaub


@Mathew thank you! It was very helpful!

@phaub to export the histogram values that you used in the previous topic and to calculate the total value, mean, and mask, should I click on the “list” command or is there another way? How can I calculate them using excel? Thank you in advance, Eugenia

Yes, click onto the List command. Then copy&paste the date from the table to Excel.
Mean, StdDev, Min, Max and Mode are displayed in the Histogram window.
You can use this values to check if your Excel calculations are correct.

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Thank you a lot for the explanation!

Sorry to bother you again, in the previous topic you calculated the “total (intensity/distances)” and the “total pixels (lenght of crack)”, I copied and pasted the date from the histogram, but I don’t understand which numbers I have to use in order to find these two values.
Thank you, E.

Sorry, what exactly is unclear?

Total intensity = Sum of all pixel intensity values
Total pixels = Number of pixels with an intensity > 0

When I analyze your image (a region around the crack) I get the following histogram:

0	1151100
1	149
2	404
3	598
4	421
5	48
6	13
7	28
8	9
9	2
10	2
11	6
12	8
13	6
14	5
15	9
16	8
17	0
18	0
255	0

What histogram values do you get?

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I get the same histogram! So the “intensity” values are, for example, 1151100 etc, and the “number of pixels” is 0, 1, 2… right?

The number of pixels (with I>0) is
149 + 404 + 598 + … + 8 = 1716

The total intensity is
149x1 + 404x2 + 598x3 + … + 8x16 = 5632