error: ‘CV_BGR2GRAY’ was not declared in this scope

Solution:
put cv_ Change bgr2gray to CV:: color_ Bgr2gray
problem:
error: ‘CV_ CALIB_ CB_ ADAPTIVE_ Thrash’s was not declared in this scope
solution:
find cv_ CALIB_ CB_ ADAPTIVE_ After the location of thresh in opencv2 library, inclde goes in

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