Question about a detail in the m.function EDGE
in [Matlab]
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From: Bang Nhan on 22 Apr 2010 15:27 "Bang Nhan" <dbang1988(a)yahoo.com> wrote in message <hqec6e$2n1$1(a)fred.mathworks.com>... > Hi Walter, > > So one thing I want to make sure, is the pw determine how large the filter mask gonna be? > In Gonzalez and Woods's Digital Image Processing using MATLAB, they mentioned that the default size for the linear filter is 3x3 matrix. So I wonder if the Gaussian filter in the Canny is also set to have the default 3x3? > > First when I saw the pw1:30, I thought that is the default size for the Gaussian filter. Is that the right thinking? If not then how may I tell how large the mask in the canny is? > > Thanks > Bang Hi I wonder if the possible width (pw=1:30) mentioned above is related to the filter size (Mask size, normally it is 3x3 or 5x5 matrices) for the Gaussian? But normally the filter size is odd number since they needs even number of pixel to surround a single pixel. And a question about filter size, does it mean the larger then filter, the better or the other way around? Am I correct to think the filter size as how large the sigma of the Gaussian is? Really appreciate your help in clarifying those parameters. Bang
From: Bang Nhan on 25 Apr 2010 02:15
> Lowering the upper limit on pw is equivalent to using a smaller sigma in > the same proportion. Thus if you specified a sigma of 10, but change the > upper limit on pw from 30 down to 1, the effect is as if you had left > the upper limit at 30 but specified a sigma 1/30 as large -- i.e., sigma > 10/30 = 1/3 in your case. Hi Walter, So what will the sigma must be if I keep the pw=1:30. How should I know how to choose the sigma as well as the low and high thresholds? Thanks |