Re: Image filters,Edge detectors

The two are different in terms of method. Edge calculates the gradient
image and then applies a threshold to find where gradient is large--
the areas where intensity abruptly changes (edges). This is done in
spacial domain. Filt2 or conv2 convolves your image with a filter,
which is done in frequency domain. With fspecial you are defining the
filter, i.e. prewitt for edge sensitivity. Although the results may be
similar, the methods are different. The latter method is generally
more independent from intensity and dynamic range. Convolution is also
probably computationally less intensive.



On Jan 8, 3:10 pm, "Farwa Bat" <fa...@xxxxxxxxxxxxx> wrote:
Thanks .... is this the only difference or there is some
more.

..................................................."Peter Bone" <peterb...@xxxxxxxxxxx> wrote in message

<fm047a$af...@xxxxxxxxxxxxxxxxxx>...

"Farwa Bat" <fa...@xxxxxxxxxxxxx> wrote in message
<fm03vr$rj...@xxxxxxxxxxxxxxxxxx>...
Hi,in matlab for edge detection sobel,prewit,etc are
available,using edge command.There is also filter2,and
conv2 using fspecial command same sobel ,prewit are
used.
Why and When I shpuld use

1)edge command and find edges.
2)filter2 or conv2 for same classical filter
(Sobel,Prewit...etc).
Plz explain the difference in detail because most of
these
are used as edge detectors.

I believe the edge command returns a thresholded binary
image whereas the others just return the filtered image
without thresholding.

.

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