Just clarifying a point about the Otsu thresholding method that lacks definition in the documentation & wikipedia articles. If you apply the Otsu method (in matlab the function graythresh) it returns a threshold value between 0 and 1.
Given 2 hypothetical grayscale images:
dark (with pixel intensities in the range of 0 to 100) and light (with pixel intensities in the range of 155 to 255)If I got an Otsu threshold of 0.75 for both dark and light images respectively, what grayscale pixel intensity would it map to in each case?
dark -> 75 and light -> 231 E.g. relative to the range of values in each imagedark -> 75 and light -> 191 E.g. relative to the range 0 to max pixel valuedark -> 191 and light -> 191 E.g. relative to the full range of grayscale pixel values (0-255)?The correct answer is the first one :
dark = 75 and light = 230, relative to the range of values in each image
graythresh uses the min and max values in the image as boundaries, which is the most logical behavior.