## Ex2 Question 1a.)

Moderator: Computer Vision

waitfor.it
Neuling
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Registriert: 14. Okt 2009 11:52

### Ex2 Question 1a.)

Hi,

the hist function of Matlab seems to normalize the gray values of the image between the minumum and the maximum value of the image before generating the 10 bin histogram instead of normalizing the values from 0 to 255. We are not quite sure why Matlab does it this way, as we think, that also the absence of values below the minimum and above the maximum might be a useful information, which can be read from the histogram. So are we supposed to discard this information also and normalize between min and max or can we keep the entire range of gray values?

krgds, Jan

diane
Windoof-User
Beiträge: 25
Registriert: 21. Jun 2009 17:33

### Re: Ex2 Question 1a.)

The normalization you use depends on what you want to do with your images.
Considering values only between min and max allows to be illumination invariant. In our case, we have images acquired in a controlled environment, so we expect the illumination to be important. Consequently, centering the values between min and max would mean loosing some information (true story).
In this exercise, I expect that you use the full range [0,255] but you can also decide to compare the performances with the [min,max] histograms.

andy-held
Windoof-User
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Registriert: 8. Feb 2007 15:22
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### Re: Ex2 Question 1a.)

In this exercise, I expect that you use the full range [0,255] but you can also decide to compare the performances with the [min,max] histograms.
Does that mean we may calculate the histogram between [min, max] ?
Woran faileds denn?

diane
Windoof-User
Beiträge: 25
Registriert: 21. Jun 2009 17:33

### Re: Ex2 Question 1a.)

Only as a second option, for comparison purposes (and it is optional), if you want to comment about it in your report.
You need to implement at least the version described in the exercise sheet (between 0 and 255).