Automated Thresholding

[Broncosbeatall]

Hi everybody,

I'm trying to have a macro automatically threshold an image based on the greyscale values. For example, for a given histogram, I want to threshold the upper 5%. How might I go about writing this? I'm rather inexperienced in macros so any help would be greatly appreciated. Thanks in advance!

Thomas Huang

[kirill8910]

Hello Thomas!

What do you mean by "upper" ?

Because if you need 5 % of max value - you can use getStatistic function like:

getStatistics(area, mean, min, max, std);

threshold = 0.05*max;

setThreshold(0, threshold);

Kirill

[kirill8910]

and getStatistics extracts these max, mean...values from histogram

[Broncosbeatall]

Thanks a lot! Sorry if i didn't clarify very well, I wanted the 95th to 100th percentile of values and didn't know what functions could do that. What you gave me helped a lot, all I did instead was do

getStatistics(area, mean, min, max, std);

threshold = 0.95*max;

setThreshold(threshold, 255);

Thank you very much!

[Gabriel Landini]

On Tuesday 28 Aug 2012 17:41:07 you wrote:
> Thanks a lot! Sorry if i didn't clarify very well, I wanted the 95th to
> 100th percentile of values and didn't know what functions could do that.
> What you gave me helped a lot, all I did instead was do
>
> getStatistics(area, mean, min, max, std);
> threshold = 0.95*max;
> setThreshold(threshold, 255);

That is not the 95th to 100th percentile of the *values*, but of the
*maximum*. Not the same thing.
You probably need to integrate the histogram to see what threshold gives you
the 5% of the values to the maximum.

Cheers,

Gabriel

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