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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.
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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 &...
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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 \\ ...
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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 ...
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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 & ...
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