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Ex1 Task3

Verfasst: 2. Mai 2012 15:54
von kleinβeta
Hallo, what is meant by "correctly normalized"

if I normalize the filter I will end up with one that only has positive values, and thus will not compute central differences any more.

I guess simply using the sobel filter
[1 2 1;
0 0 0;
-1 -2 -1]
is not what you want here as its not exactly the values for a gaussian.

so what should we normalize the filter to? should rows sum up to 1 (or -1) or should the maximum value of a row be 1 or something else?

Re: Ex1 Task3

Verfasst: 2. Mai 2012 20:29
von Toobee
no, you shall use the central difference, which is
(1/2) * [1,0,-1] (see slides of previous year if they haven't upload them yet)

next you have to come up with the gaussian filter in x direction. Combine the 3x1 and 1x3 filter and you should have the needed 3x3.

Re: Ex1 Task3

Verfasst: 3. Mai 2012 15:06
von qgao
kleinβeta hat geschrieben: so what should we normalize the filter to? should rows sum up to 1 (or -1) or should the maximum value of a row be 1 or something else?
sum to 1 for the Gaussian filter.

Re: Ex1 Task3

Verfasst: 4. Mai 2012 15:36
von dummdidumm
Another question regarding task 3: It says "For every edge candidate pixel, consider the grid direction (out of 4 directions) that is “most orthogonal" to the edge". Does this mean that we only have to care about all horizontal and vertical edges and can discard all other edge-vectors?