How to get "mean" or "average" from image statistics?

[konstantin]

When I type:

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identify -verbose 1.bmp

I can see:

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Channel statistics:
    Pixels: 57600
    Gray:
      min: 0 (0)
      max: 255 (1)
      mean: 254.996 (0.999983)
      standard deviation: 1.06249 (0.00416663)
      kurtosis: 57595
      skewness: -239.994
      entropy: 0.000299591
  Colors: 2
  Histogram:
         1: (  0,  0,  0) #000000 gray(0)
     57599: (255,255,255) #FFFFFF gray(255)

So I can see the "mean" calculated data: 254.996 (0.999983)

But when I type:

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identify -format "%[mean]" 1.bmp

I get :

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65533.9

How can I get the correct result for the mean and what is its exact meaning?

[fmw42]

You need to convert the [mean] from the Qrange of your install to the range 0 to 255. That is where the numbers in parenthesis come in. They are always in the range 0 to 1. So better to do:

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convert 1.bmp -format "%[fx:255*mean]" info:

%[mean} gives values from 0 to quantumrange for you compile

%[fx:mean] gives values from 0 to 1