Questions tagged [image-processing]
70 questions
168
votes
9 answers
Could Legolas actually see that far?
The video “How Far Can Legolas See?” by MinutePhysics recently went viral. The video states that although Legolas would in principle be able to count $105$ horsemen $24\text{ km}$ away, he shouldn't have been able to tell that their leader was very…
Ali
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29
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3 answers
How to recover an unfocussed image
If the lenses in a camera are not set correctly, the intended subject will be "out of focus" in the resulting image. There seems to be no loss of information here. The photons are just steered to the wrong CCD element. If we knew the exact…
Logic Knight
- 393
29
votes
4 answers
How specifically does an MRI machine build an image from received radio waves?
Unlike the excellent Wikipedia page on ultrasound imaging, the one on MRI only explains the principle theory behind MRI - that oscillating strong magnetic fields cause water molecules to emit radiowaves - without explaining how his is applied to…
Mr. Boy
- 1,016
23
votes
7 answers
Why are light rays able to cross each other?
See the image first:
Why are light rays able to cross each other? Air isn't able to.
Harsh Kumar
- 807
18
votes
6 answers
Is there any advantage in stacking multiple images vs a single long exposure?
Suppose I have a source object that is not time varying, to be concrete let's say it's a galaxy. Is there anything additional that can be learned or done with multiple short exposure images of exactly the same field as compared to a single long…
Kyle Oman
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14
votes
5 answers
Technical explanation of "Hitachi lensless camera"
Hitachi is bragging about a thin lensless camera. I can't find any technical information on how it works---just press releases etc.† Can anyone work backwards from the published descriptions to reconstruct how this works?
The "concentric-circle…
Steve Byrnes
- 17,082
14
votes
3 answers
Is it possible that a person with myopia will see a blurry picture as normal?
I am trying to process an image in good quality to appear blurred to a normal person and good to a person suffering from myopia
as seen in this source.
Is it possible that a picture that is blurry will appear normal to a person suffering from myopia…
Sohail Arif
- 143
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10
votes
2 answers
What is meant by 2D fourier transform of an image?
I have some questions about this interesting concept I came across about 2D Fourier transform, please...
Firstly, the Fourier transform of a 1D signal (such as a sound recording) is as follows:
The first picture is a graph of the real sound file,…
user315366
9
votes
3 answers
Verifying radiation measurement smart phone applications
I've stumbled upon a strange class of Android applications lately. (And I'm sure such applications are available for other platforms too.)
These apps claim the ability of detecting radiation. The mechanism would be gamma rays hitting the light…
netom
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5
votes
1 answer
Fresnel transform
How is it possible to encrypt multiple images using fresnel transform and inverse the operation to de-multiplex those images?
SKM
- 303
5
votes
1 answer
Calculation Of Resulting 2D Image After Lens
This is a tough question!
I would like to calculate how an image (a real 2D photograph) looks if I place a lens at a certain distance d1 from it and I observe it at a certain distance $d_2$.
It is frustrating. All textbook always only treat 1D…
henry
- 111
5
votes
3 answers
Why are $L^2$ spaces preferred over $L^1$ spaces in some applications?
In various applications where we are dealing with electromagnetic or acoustic waves, such as medical imaging, we use the space $L^2$ or the related Sobolev space $W^{1,2}$. I have never seen a reason given for this. Does anyone know why these spaces…
ManUtdBloke
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4
votes
0 answers
Maximum-Entropy Method deconvolution implementation?
I am looking for an implementation of the Maximum Entropy Method for image deconvolution, ideally in MATLAB or Mathematica.
I'm trying to reconstruct an image from fringe visibilities, as is often done in aperture-masking interferometric astronomy,…
user29724
- 41
4
votes
0 answers
Difference between Fast Fourier transform of a 2D lattice image and its reciprocal lattice image
I have constructed an image of nXn pixels with each pixel having values either 0 or 1. I have added circles in the form of square lattice with definite period a.
The image basically looks like (a).
If I perform Fast Fourier Transform I get this…
Ajith
- 41
4
votes
1 answer
Image Reconstruction:Phase vs. Magnitude
Figure 1.(c) shows the Test image reconstructed from MAGNITUDE spectrum only. We can say that the intensity values of LOW frequency pixels are comparatively more than HIGH frequency pixels.
$$
f(x,y)= ∑_(u=0)^(U-1)∑(v=0)^(V-1)\ |F(u,v)|…
sagar
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