Search found 6 matches

by c_joerg
2017-12-08T02:16:12-07:00
Forum: Users
Topic: why is median of a sequence of images slower than mean
Replies: 13
Views: 4103

Re: why is median of a sequence of images slower than mean

Also the fuction does not return a intensity value but the full color pixel with the median intensity! Yes of course. The intensity value is only for sort of median. On the end I want to have a full color picture. That’s exact what my MATLAB code is doing. And again my result is similar to convert....
by c_joerg
2017-12-07T01:43:15-07:00
Forum: Users
Topic: why is median of a sequence of images slower than mean
Replies: 13
Views: 4103

Re: why is median of a sequence of images slower than mean

IM doesn't make the images gray, so needs to do that within the comparison function that is called by the sort function. (The code is in statistic.c.) Not??? http://www.imagemagick.org/Usage/layers/#evaluate-sequence The "-evaluate-sequence Median" will look for the pixel which has an intensity of ...
by c_joerg
2017-12-06T23:59:02-07:00
Forum: Users
Topic: why is median of a sequence of images slower than mean
Replies: 13
Views: 4103

Re: why is median of a sequence of images slower than mean

There are more optimal ways to compute the median than what IM does. Search Google for "fast median filter". I don’t think the median code is the problem. In the MATLAB code, just 0,7s(20%) of the time is for the median. How many comparison are needed when sorting 3 elements? Perhaps 6. So we do 12...
by c_joerg
2017-12-06T01:41:00-07:00
Forum: Users
Topic: why is median of a sequence of images slower than mean
Replies: 13
Views: 4103

Re: why is median of a sequence of images slower than mean

I am splitting the post into a separate topic. Thanks… EDIT: On sorting, yes, this always happens, even when there is only one image. It can’t be only the sorting on the median processing… As I said before, I’m doing a lot of image processing in ‚MATLAB‘ for time lapse. On most parts a got similar ...
by c_joerg
2017-11-30T08:24:27-07:00
Forum: Users
Topic: why is median of a sequence of images slower than mean
Replies: 13
Views: 4103

Re: median of a sequence of images operating pixel-by-pixel

Thanks for response… Median takes longer than mean because median populates an array with pixel values, sorts it, and chooses the middle value. Mean simply adds, and divides by the number of images. I know how to calculate a median. A median of 3 is not a big thing but probably always a sort routine...
by c_joerg
2017-11-30T07:12:11-07:00
Forum: Users
Topic: why is median of a sequence of images slower than mean
Replies: 13
Views: 4103

why is median of a sequence of images slower than mean

I’m wondering, why the calculation of a median of 3 images takes so much more time than mean. Now I understand a little bit more about it.

How is the intensity calculated? Just by (R+G+B) /3?
What about the ambiguities? Only a red, green or blue pixel could have the same intensity…