How to get region information

I am thinking to find the length but not sure how to do that.

An example image is shown below:

From Original image I have tried to get some results but I am stuck.

I am looking to find the red marked thread height from the following figure. Any help will be appreciated.

Answer 1

[Image Analyst]

Run along the columns finding the hairs and subtracting from the skeleton

% Preallocate arrays for heights above and below the core skeleton.
hairHeightsAbove = zeros(1, columns);
hairHeightsBelow = zeros(1, columns);
% Loop over all columns, finding distances above and below for each column.
for col = 1 : columns
  % Find row of hair sticking above the core skeleton.
  hairTopRow = find(hairs(:, col), 1, 'first');
  % Find row of hair sticking below the core skeleton.
  hairBottomRow = find(hairs(:, col), 1, 'last');
  % Find row of the core skeleton.
  skeletonRow = find(coreSkeleton(:, col), 1, 'first');
  % Compute distances of hair ends to the core skeleton.
  hairHeightsAbove(col) = abs(hairTopRow - skeletonRow);
  hairHeightsBelow(col) = abs(hairBottomRow - skeletonRow);
end

[Image Analyst]

Post the original gray scale, non-annotated image.