@malfet Good job! Could you add test for the new option too?

@asmorkalov, sure. Is it OK if I have a separate commit that adds the test (since, as far as I can see CV_8UC1 Otsu is not covered by unit tests at the moment as well)? And should it extend test_thresh.cpp or add a new one?

Added unit test for both 8u and 16u Otsu thresholding to PR

@malfet Good job! Thanks for the test. Could you look at CI status on Windows. CI bot and tests report memory access issue: https://pullrequest.opencv.org/buildbot/builders/precommit_windows64/builds/23771/steps/test_imgproc/logs/stdio

[ RUN      ] Imgproc_Threshold.accuracyOtsu
C:\build\precommit_windows64\opencv\modules\ts\src\ts.cpp(616): error: Failed
	failure reason: Invalid memory access
	test case #1
	seed: df8f7585c259522a
-----------------------------------
	LOG:
General failure:
	Invalid memory access (-5)
-----------------------------------
[  FAILED  ] Imgproc_Threshold.accuracyOtsu (3 ms)

Looks like Windows doesn't like 256Kb being allocated on stack. Switched to cv::Mat as storage for histogram arrays.

Try to run failed test under valgrind.

Windows issue was definitely stack size limits. Latest failure on Linux was my mistake in assert, corrected in latest revision of the commit.

@asmorkalov is there anything else you want me to modify in the PR?

@malfet Thanks a lot!

@malfet friendly reminder.

@alalek sorry for the late reply. Can you give it another look?

@malfet do you have chance to fix remarks?

@asmorkalov thank you for the feedback. Updated.