Unformatted text preview: inches on the table to squares on the
table, so the mapping problem was solved.
To find the letter an edge filter was applied over the letter…
To find the letter T we have chosen to use edges because we were thinking that edge present invariance on the table. We processed in 3 steps:
First, we create a filter of the edge of the letter that we are looking for. We take a small picture of
the letter on the table with our camera and we apply Sobel operators to detect edges. Sobel operators are
explained in the step 2.
Then we applied edge detector to the all table. To compute a discrete approximation to the
gradient, we used Sobel operators too, we have convolved the image of the table with 2 masks. They
detect vertical and horizontal edges, respectively.
1 0 1
2 0 2
1 0 1 and 1 2 1
0 0 0
1 2 1 And finally we convolute the matrix resulting from step 2 with the filter. The maximum value
should be the letter. But when we try we do not find the letter but some point in the border. Indeed the
border has two main particular...
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 Fall '12
 ThomasTrappenberg
 Computer Science, Machine Learning, Sobel, 2 meters

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