how to cal low threshold and high threshold

[ZhuJD-China]

       "{low            |20        | low threshold                 }"
                    "{high           |40        | high threshold 

[jk3456a]

I also have the same question. I use the algorithm on images with different exposures. The default settings are not suitable for all exposures

[ZhuJD-China]

Perhaps you can switch to a different edge detection method before the first step and before finding the contour points.