Equalize the Brightness in an Image

Consider the following image that has been acquired under uneven lighting:

In[1]:=

img=

;

If no empirically obtained flat-field image is available, one can try to estimate a flat-field image by fitting a model. Obtain a foreground mask to identify the parts of the image that should contribute to flat-field modeling:

In[2]:=

mask=Erosion[ColorNegate@Binarize[ColorDistance[img,Gray],0.3],1]

Out[2]=

Perform a polynomial fit to obtain a flat field and utilize it for a subsequent brightness equalization in each color channel. Brighten the result by applying

Lighter

:

In[3]:=

Lighter[ColorCombine@Map[imgBrightnessEqualize[img,Maskingmask],ColorSeparate[img]]]

Out[3]=

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