Tagged Questions

This tag covers signal processing where input is an image, such as a photograph or video frame and the output could be an improved or altered image, parameters related to the image or information about features within the image.

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Problem with image alignment/warping

I am currently working on image alignment. I start with a normal image and then use matlab's imrotate to rotate it 1 degree. Afterwards I calculate my warping matrix and align the image using imwarp. ...
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Segmentation of small artifacts - Image Processing

I am working on a task of segmenting small artifacts from a set of images like below: I am looking for a generic approach, but unsure of what to search? I tried looking at density flow analysis, but ...
48 views

How to calculate a Hann-LP kernel for image processing

I'm currently studying for an exam in image processing and stumbled upon a exercise which i could not answer and my professor will not be available before the exam anymore. The exercise goes as ...
67 views

What is the difference between the terms color Intensity and color Saturation?

In Digital Image Processing, what is the difference between the intensity and the saturation of a color? How would you explain the difference to a newbie?
130 views

I'm working on a project of applying Active Shape Model to locate tooth in dental radiograph. For those familiar with the technique, I'm currently trying to sample along normal vectors for each ...
40 views

Basis functions in DCT

I'm new to Discrete Cosine Transform (DCT) and I have a question relating to basis functions. In DCT, basis functions are defined by: \alpha_p\alpha_q\cos\frac{\pi \left(2m+1\right)p}{2M}\cos\frac{\...
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The signal in MRI

I am trying to understand the signal formation in MRI and have a confusion. I understand that in the presence of the external magnetic field $B0$, the protons are precessing at the frequency given by ...
35 views

Fourier Transform of 2D signals

Hello I've been trying to solve this one for a while and I didn't come up with any solution. Given two 2D signals $g(x,y)$ and $f(x,y)$ as that $g(x,y)=f(ax+by, cx+dy)$ and that the Fourier transform ...
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How to classify images based on the amount of colors in the image?

I have a problem where all images have the same object; however, these objects can either have number_of_colors<=3 OR number_of_colors>3 and images are not labeled. My attempt starts by ...
41 views

Image Rotation using 3 Shears, Implemented using FFT-based Shifts

So I'm trying to rotate an image using the 3-pass shear. We're implementing the 3 shears in Fourier space, so we're taking the the rowise/colwise FFT, then multiplying it with e^ikx, with necessary k'...
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Can Inpainting and Texture Synthesis address same types of image-restoration problems?

Are In-painting and Texture Synthesis used to address different types of problems? For instance, can both methods operate on damaged Old photographs and wooden textures? Are these methods ...
38 views

What is the difference between MRF and Total variation in noise removal?

I have a general question in image processing. I have a noisy image. I would like to classify the noisy image into some regions. Two famous approaches I can use are: MRF/Gibbs MRF: Model the spatial ...
32 views

I have a 4-channel image (.png, .tif) like this one: I am using OpenCV, and I would like to add padding of type BORDER_REFLECT around the flower. ...
28 views

How can we add energy to an image using matlab?

In under water images due to attenuation of light in water ,image appears to be blue so in order to compensate that attenuation ,I calculated the energy of light that is attenuated and i am unaware ...
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Using multiple input modalities in Computer vision

This might be a rather broad question, but I hope it will result in a couple of insights or even recipes people have used for the following problem: Suppose you have ...
63 views

What would produce this “hamburger” corruption on images?

I have an image that has gone through an unknown number of jpeg and webp conversions (at least one but more likely 2+). Currently this image is a JPEG and contains corruptions in single color or mild ...
51 views

How to achieve image straightening as cam scanner does?

Is it possible to achieve image straightening as cam scanner does I mean selecting a non-rectangular region and converting it to a rectangular region as an image. I can only do re sizing and crop ...
43 views

Gibbs energy in MRF

I am stucking in Gibbs energy in MRF. Firstly, let us define some definition Let $S = {(i, j)|1 ≤ i ≤ m, 1 ≤ j ≤ n}$ be the set of sites of a rectangular lattice for a 2D image of $m \times n$ ...
18 views

Which kind of noise will show benefit with Guided filter

I am using guided filter function in MATLAB img_filtered = imguidedfilter(img_noise) I knows that guided filter is very good to preserving edge in noise image. ...
75 views

Generate a nonuniform illumination (bias field) 2D image

I am creating a nonuniform illumination in MATLAB R2015. The nonuniform illumination (known as bias field) is defined as Nonuniform Illumination (intensity inhomogeneity) which manifests itself as ...
418 views

Blending artifacts in OpenCV image stitching

I am using OpenCV to blend a set of pre-warped images. As input I have some 4-channel images (*.png or *.tif) from where I can extract a bgr image and an alpha mask with the region related to the ...
62 views

image type after an ifft reconstruction

I reconstruct images from MRI k-space using ifft and root-sum-of-squares method. ...
88 views

How does salt and pepper noise occurs in an image

How does salt & pepper noise occur? And, what are some techniques to remove it?
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white noise in images

For digital images, noise is assumed to be additive gaussian white noise. I remember noise in images is considered as high frequency. However, from the link https://en.wikipedia.org/wiki/White_noise, ...