3 votes
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Why doesn't JPEG file format follow indexed color technique?

Because JPEG is for «natural images» containing smooth gradients, while indexed color is great for many kinds of artificial images containing sharp transitions and a single color background.
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  • 2,186
3 votes

Metric for image sharpness?

I don’t know of any method that can measure sharpness in an arbitrary image, and presume it is impossible to distinguish a sharp picture of a smooth color transition form a blurry picture of a sharp ...
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  • 1,023
3 votes

What does hue, saturation and intensity means in image processing?

To display a color image, each pixel needs to have those three values: Red, Green, and Blue. Sometimes there is a fourth, Alpha, channel, but let's ignore that for this question. What you're seeing in ...
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3 votes
Accepted

Noise Reduction - noisy lines

I just used the method suggested in this older DSP.SE post and it seems to work: I did this manually by first loading the image: ...
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  • 22.5k
2 votes
Accepted

How to exclude diffuse moving features in a stack of images

So I tried Gillespie's suggestion of TV. First, I got the individual frames from your GIF out using ffmpeg: ...
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2 votes

How to exclude diffuse moving features in a stack of images

Assuming there is no underlying data-specific mechanism that can be exploited, I think your best bet would be Total Variation Denoising. It reduces noise by minimizing the variance of the data, ...
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  • 598
2 votes

What Is the Difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat Wavelet?

Let's see how DoG approximates LoG for the 2D case (for an image, e.g.). By derivative theorem of convolution (by associativity and commutativity), $$\nabla^2[f(x, y) \ast G(x, y)] = \nabla^2 G(x, y) \...
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2 votes

Fixing distortion in photographic reproductions

I answered a related question in SO some time ago. Briefly, you can work your setup through a standard camera calibration procedure, and you have the option of "freezing" the focal length to ...
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1 vote

Image warping with heat map that "pulls" on pixels

You need to split the problem into two: Compute the motion (the velocity vectors, aka flow) Resample the image I assume that computing the motion is expensive, and you want to do it on less pixels ...
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1 vote

Does downsampling an image twice result in a "worse" (or different) image than downsampling once

That depends on the methods and filters involved. To actually find out you could either do the math: take the impulse responses and everything else that matters and compare the two approaches. try ...
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1 vote
Accepted

Fixing distortion in photographic reproductions

In a general setting, multiple observations of a calibration target are needed because otherwise the focal length parameter(s) and principle point parameters are coupled so you would not be able to ...
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  • 146
1 vote

Copy an object (along with bounding box) from one image and paste on different image (only background)

You need a mask. That's literally what you want to do, only copy the object, not the whole rectangle containing it. So, you need the info where the object is, and where it's not. That is the mask. So, ...
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1 vote

Why doesn't JPEG file format follow indexed color technique?

Besides Knut’s argument that indexed color cannot represent color gradients well, we can also look a the compression method. The JPEG compression relies on similarity between neighboring pixel colors. ...
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  • 1,023
1 vote

How to exclude diffuse moving features in a stack of images

It seems that the «artifacts» roll vertically at constant speed? I wonder if that could be exploited somehow. I.e. a signal model consisting of desired signal + uncorrelated noise + «slow innovation, ...
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