algorithm - detect white areas with sharp boundary -


in grayscale image shown below, how can accurately detect white region having sharp boundary (marked red color)?

in particular image, simple thresholding might work, however, have several images in there similar areas around corner of images want ignore.

also, there might more 1 regions of interest, both having different intensities. 1 can bright in example image, other can of medium intensity.

however, difference between interested , non-interested areas follows:

  1. the interest areas have sharp defined boundaries.

  2. non-interested areas don't have sharp boundaries. tend gradually merge neighbourhood areas.

no-flash/flash ratio image

image without mark testing: image test

when sharp boundaries, have think gradient. sharper boundaries, bigger gradient. therefore apply gradient , see stronger around shapes want segment.

but in case, can observe area want segment brightest. try noise reduction (median filter) plus convolution filter (simple average) in order homogenize different zones, thresholding keeping brightest/right peak.


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