# Questions tagged [image-processing]

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### How to extract depth of a pixel from an image?

I'll have a few pictures that show the same scene, but only a few things move around a little bit. Now I don't have an information about any size in real life but I'd like to extract a scaling factor ...
• 125
2k views

### 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 ...
• 393
282 views

### Why do we need the eigenvalue? [closed]

Now I'm trying to review about the image noise. http://people.csail.mit.edu/celiu/denoise/estnoise/and I have found an article about the eigenvalue. Why do we need the eigenvalue, what is its use?
• 115
1 vote
76 views

### What is the concept of phase congruency?

I am beginner in signal processing. I am studying the importance of phase in signals. I want to know about Phase Congruency, but there is very little information available on internet. So can anybody ...
• 229
267 views

### Measuring typical distance between patches using 2D Fourier Transform

I need to extract information about the typical distance between the black patches in an image like the one I attached here. I tried to perform 2D FFT on it (using OpenCF fdt function in Python), but ...
• 133
1 vote
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### How to measure the size of a laser dot?

I'm not a physicist, that's why I'm asking you if there is maybe an easy way (e.g. a mathematical law) to measure the size of a laser dot, or its diameter. The setup It contains a laser, a high ...
• 125
1 vote
398 views

### What makes a system linear?

Lately I have been interested in Image Processing, and I started by following this course: https://class.coursera.org/digital-001, which is quite awesome in my opinion. But in weeks 2, Linear Shift-...
• 113
3k views

### 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 ...
• 655
334 views

### Can a point source be located more accurately out-of-focus or in-focus?

Let's say I am taking a picture, and I know a priori that the image is of a single ideal point source of light at infinity. With a perfect imaging system in focus, the image shows an Airy disk. I ...
• 16.2k
24k views

### 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 ...
• 5,865
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### Phase and amplitude information of an image

By applying Fourier Transform to an image we can get its magnitude as well as phase spectrum. A magnitude spectrum describes how various frequencies are attenuated and accentuated in that image but ...
• 127
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### 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)=...
• 141
2k views

### 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 ...
• 986
319 views

### How do they draw collision pictures in Atlas?

Is the picture below a simulation? How to they draw these pictures? The picture is from here.
• 561
2k views

### How do you define an aperture for seismic data processing?

Lets consider this in marine seismic processsing. I am assuming you know what a first order primary reflection is, if not, I can define it. Ok, so if we were to have a source $(S)$ and receiver $(R)$...
• 133
408 views

### 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 ...