In[]:=
​
In[]:=
grayscale=ColorConvert
,"Grayscale"​​n=ImageData[grayscale]​​ListPlot[n[[All,4]]]​​q=ListInterpolation[n[[All,4]]]​​FindMinimum[q[x],{1,88}]
Out[]=
Out[]=
Out[]=
0
20
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80
0.2
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Out[]=
InterpolatingFunction
Domain: {{1.,88.}}
Output: scalar

FindMinimum
:The function value 1 is not a real number when the arguments are {1.}.
Out[]=
FindMinimum[q[x],{1,88}]
​
InterpolatingFunction
:Input value {-0.525771} lies outside the range of data in the interpolating function. Extrapolation will be used.
Out[]=
0.0713373,InterpolatingFunction
Domain: {{1.,88.}}
Output: scalar
1.85313
{0.0713373359080983`,{1.8531316378718876`}}
​
​