3
votes
Accepted
Detecting corners using structure tensor matrix
I'll simply present a series of results relevant to this question.
Note that eigenvalues of this matrix are non-negative
Let $x = [u\ v]^T$
$$x^TMx = [u\ v]
\begin{bmatrix}
I_x^2 & I_x I_y \\
...
- 447
2
votes
How to perform Spatial derivative calculation?
What you should do instead to calculate $I_x$:
$$
\begin{align}
I_{x}(x,y)&=\frac{\partial I(x,y)}{\partial x}\\
&=I(x+1,y)-I(x-1,y)\\
&=
\begin{bmatrix}5& 7 & 11\\
9 & 12 &...
- 25.2k
2
votes
Accepted
Given the 4 corners of two QR codes on a photographed sheet of paper, can we get a deskewed rectangular image?
The solution is to use an "homography" / aka "projective transformation" (see this PDF, page 16).
Here is a working code showing how to do it with Python + OpenCV.
- 1,267
1
vote
Corner detector vs feature detector
A couple of confusions here.
Features refer to some form of lower dimensional descriptors that explain a (potentially local) region of interest. They are useful in converting the appearance into ...
- 5,465
1
vote
Detect grid corner
Threshold the image to convert into binary image.
Check whether it is a corner or not by dilating with these kernels separately on corners detected by corner detection.
$$E_1 = \begin{bmatrix}0 & ...
- 700
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