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Alternate Names

Untitled

In the first line it reads "... Otsu method ..." Shouldn't it be "Otsu's Method"? or "the Otsu method" also, the article is not found if you search for otsu's algorithm. ive seen it reffered to as such in a book and a few articles as both otsu's algorithm and otsu's method. someone should probably address this - Pikez33
Albert Cruz 03:29, 12 June 2008 (UTC)[reply]

Some references to articles that reffer to Otsu's method as Otsu's algorithm

Y. Liu and S. N. Srihari. Document Image Binarization Based on Texture Features. Pattern Analysis and Machine Intelligence, IEEE Transactions on. 19(5):540-544, 1997.
Y. Solihin and C.G. Leedham. Integral Ratio: A New Class of Global Thresholding Techniques for Handwriting Images. Pattern Analysis and Machine Intelligence, IEEE Transactions on. 21(8):761-768, 1999.

There are many more that I haven't included, but I think it's safe to say that it's also known as Otsu's algorithm. -Albert Cruz 18:18, 16 June 2008 (UTC) Pikez33

I went ahead and linked "otsus method" to this page, as it would be a common error when searching for this algorithm. will wait to link "algorithm" Albert Cruz 18:36, 16 June 2008 (UTC) Pikez33

done Albert Cruz 04:45, 30 June 2008 (UTC) Pikez33

Does anybody know if this method is known also as Ad-hoc algorithm. I do not think so, and the name seems weird to me, if nobody complains I will remove this. --Tomash (talk) 22:04, 16 February 2008 (UTC)[reply]

Removed. --Tomash (talk) 16:54, 1 April 2008 (UTC)[reply]

I did an extensive search and Otsu did not reffer to his image segmentation algorithm as ad-hoc. there are no references to an algorithm by Otsu under the name of ad-hoc algorithm/method in the context of image processing. Albert Cruz 18:18, 16 June 2008 (UTC) Pikez33

Visual example

this page needs a visual example of a grayscale image thresholded using Otsu's Albert Cruz 23:15, 1 July 2008 (UTC) Pikez33

I've linked a public domain image (original) and it's otsu's threshold result. they could probably be better formatted Albert Cruz 03:32, 3 July 2008 (UTC) Pikez33

General/Content

I'v changed from Category:Computer vision to Category:Computer vision stubs since this articles needs mora material to make it readable.--KYN 07:01, 22 March 2006 (UTC)[reply]

I thought this was a good description from the web - since the actual paper by Otsu is pre-internet: http://sampl.ece.ohio-state.edu/EE863/2003/ee863-9.ppt The thresholds are exhaustively searched (there are only 254 possible for greyscale images). For each threshold, Otsu aims to minimize variance*probability of points less than threshold + the variance*probability of the remaining points. This minimizes within-class variance, and maximizes between-class variance. In practice the variances are not actually computed, because a marginally more efficient incremental method was suggested by Otsu.

I changed the description so that it is clear that variances are not computed. --Tomash (talk) 22:10, 16 February 2008 (UTC)[reply]

I am currently a student at UC Riverside with some expertise in computer vision, and will try to improve this article - Albert Cruz 22:28, 8 August 2007 (UTC) Pikez33

References

the references at this point have been well formatted; however there is some information missing on sources 2 and 3 (Ping-Sung Liao and Tse-Sheng Chen and Pau-Choo Chung (2001) and N. Otsu (1979)). the volume and issue numbers need to be checked. Albert Cruz 03:32, 3 July 2008 (UTC) Pikez33

Dynamic Range

The article states (misleadingly) that the threshold applies to the dynamic range of pixel intensities present in the image. This comment (and the reference provided for it) refers to the internal MATLAB function graythresh that implements Otsu's algorithm in this way. In fact the description of the algorithm given here, as well as all the pseudo-codes seem to be providing a real threshold value, and do not seem to be using the dynamic range. This is what it appears to me, but I have done neither experimentation, nor verification. If someone else does that, they could fix the article. If not, I will do so when I have to time to verify my claim. Arif Zaman (talk) 12:37, 29 October 2015 (UTC)[reply]

Now I have done a good amount of experimentation, and read the source code of MATLAB's implementation of Otsu's method. It is patently clear that the stackexchange article that was referred to was erroneous. I have made a comment with details there as well. Since most algorithms return a threshold value directly anyway, this comment is only with reference to a MATLAB function. I am going to remove the entire paragraph that creates this confusion. Arif Zaman (talk) 02:59, 30 October 2015 (UTC)[reply]

Psuedo-code

This pseudo code has nothing to do with Otsu's Method. This method's describes the iterative method to obtain the ideal threshold by Gonzalez and Woods [2002].

Pseudo code is an example of K-mean method... not Otsu's

Pseudo-code now reflects what I think is Otsu's algorithm. --Tomash (talk) 22:10, 16 February 2008 (UTC)[reply]

Representation of Equations

this article seems to focus on otsu's method being used only in cases when there is a foreground and background. also, there is a mathematical representation of otsu's method

@@ Line 36: / Line 36: @@
 ==Dynamic Range==
 The article states (misleadingly) that the threshold applies to the dynamic range of pixel intensities present in the image. This comment (and the reference provided for it) refers to the internal MATLAB function graythresh that implements Otsu's algorithm in this way. In fact the description of the algorithm given here, as well as all the pseudo-codes seem to be providing a real threshold value, and do not seem to be using the dynamic range. This is what it appears to me, but I have done neither experimentation, nor verification. If someone else does that, they could fix the article. If not, I will do so when I have to time to verify my claim. [[User:Arif Zaman|Arif Zaman]] ([[User talk:Arif Zaman|talk]]) 12:37, 29 October 2015 (UTC)
+Now I have done a good amount of experimentation, and read the source code of MATLAB's implementation of Otsu's method. It is patently clear that the stackexchange article that was referred to was erroneous. I have made a comment with details [https://stackoverflow.com/a/33427884/1143539 there] as well. Since most algorithms return a threshold value directly anyway, this comment is only with reference to a MATLAB function. I am going to remove the entire paragraph that creates this confusion. [[User:Arif Zaman|Arif Zaman]] ([[User talk:Arif Zaman|talk]]) 02:59, 30 October 2015 (UTC)
 ==Psuedo-code==