Image Processing Reference
In-Depth Information
(a)
(c)
(e)
(b)
(d)
Fig. 11.5. Electronic circuit and transistor detection. a,b. the original and the prototype. c,d.
|I 20 | and I 11 . e. GHT accumulator with 2 π/ 256 angle resolution (from [22]). The circle is
inserted to show the location of the peak
A ( x j ,y j )=
l
δ ( θ ( x j + x l ,y j + y l )
φ ( x l ,y l ))
(11.70)
where l runs over the edge elements of the prototype, and φ ( x l ,y l ) is the direction
of the prototype edge. The θ ( x j + x l ,y j + y l ) corresponds to the direction of the
edge at the position ( x j + x l ,y j + y l ) in the contour image, whenever there is an
edge pixel, or i
is purely symbolic and serves to make
θ different from φ , because expected contours modeled by the prototype may be
missing in the contour image. In such instances this will generate a zero contribution
(vote) from the δ -function. The array A ( x j ,y j ) represents the vote accumulator and
can be constructed on the same grid as the image itself. Figure 11.5 shows the result
of detection of a transistor in an electronic circuit picture.
. That θ is defined to be i
11.6 Voting in GST and GHT
The parameter estimation of the generalized structure tensor is more than a correla-
tion of edge magnitudes. It carefully takes into account the directions of the edges,
too. Here we show that the GST detection extends GHT, to a complex GHT in which
the votes are allowed to assume complex values.
The GHT accumulator, A ( x j ,y j ), can be compared to an estimation of I 20
at
local images around all image points,
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