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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16 views

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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0answers
8 views

How to correctly implement spectral activity measure (SAM) for image quality assessement

I am trying to compute the spectral activity measure (SAM) which is a well-known image quality assessment metric. I used MATLAB to implement this method, which can be computed as follows: $$ SAM=\...
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2answers
47 views

Measure similarity between quantized grayscale images

I want to measure the similarity between quantized grayscale images (8 levels) that mostly depict organic patterns found in nature, say pigmentation patterns in animals (zebra pattern, leopard spots,.....
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1answer
31 views

audio recording conversion to decibels(db) [on hold]

I have several audio recording like the crying of a baby, the sound of a moving vehicle etc.How can I convert the audio recording to Decibels (db)value
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0answers
4 views

LMN color model vs YIQ color model

LMN color model - L - luminance M & N - Chrominance feature YIQ color model - Y- luminance I & Q- Chrominance feature except formula what is difference between these two?
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9 views

how to open image according to the selected image [closed]

i am using the gui and code for selecting an image is as follows: ...
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0answers
48 views

Is the formula of this image filter correct?

Consider this research paper. In the section 4.1 (Preprocessing), they gave us a formula of the kernel, Where, In the formula, we see that, v is never used....
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3answers
49 views

Why does an image get blurry beyond a limit of zooming?

As we have came cross a phenomenon where a picture get blurry and more blurry as we zoom in a image beyond a limit. Why does it happen?
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1answer
32 views

Obtaining the size of objects from an image

My objective is to be able to obtain the size, in pixels, of objects in images I'm receiving from a camera. I've tried two approaches thus far, both working to some extent, and I'm wondering if there'...
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1answer
24 views

BiLinear Downsample and Upsample Equivalent Filter or Operation

Let's say I have an image mInputImage with numRows and numCols. I resize it using Bilinear ...
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1answer
33 views

Cross-correlation and auto-correlation of an image using $\tt fft$

I'm working on a project where I have to find the auto-correlation and cross- correlation of types of pixels in an image: I am using MATLAB and my code for the autocorrelation is: ...
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1answer
48 views

Help in problem formulation for estimation of image as a feature vector - SISO or MIMO FIR channel model?

Based on the paper Blind Image deconvolution: A feature vector is a list of numbers used to represent an image. The feature vector for my case takes values as symbols $-1,1$. An instance or an ...
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3answers
20 views

Is a real Grayscale image always 8 bit per pixel indexed?

I tested several Grayscale images downloaded from the Internet. Some of them are 8bpp indexed while others are 24bpp (true colored). Looks like different Grayscale images have different depths. For ...
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0answers
28 views

Measuring sharpness/contrast for autofocus

For the implementation of an auto-focus for the raspberry cam I need some measure of image sharpness. I used the following sample picture: The first approach was to compute the shannon entropy of ...
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1answer
34 views

Why can FFT only operate on images with specific properties?

Can FFT only operate on Grayscale images? If Yes, why? Can FFT only operate on images with dimensions of power of two? If Yes, why?
3
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1answer
61 views

What transformation (or similarity metric) is rotation, shift, and scale invariant?

I have an algorithm to to detect copy-move forgeries in images. I used block matching to detect regions of an image that were forged with copy-move forgery and highlighted the alleged areas. For block ...
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3answers
67 views

Where and how do an Image and a complex number meet?

I am trying to implement a Gabor Filter bank. Gabor Filter uses a complex function. How do the filters like Gabor Filter operate on an Image? Does a complex number represent an entire Image or only ...
0
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1answer
36 views

Poster detection in OpenCV?

I'm really new in image processing, so please sorry I'm a newbie. I tried to use the squares.cpp for detecting posters (since they usually are rectangles) without using expensive feature detectors (...
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1answer
24 views

Global vector descriptor

Usually, algorithms as SIFT, SURF and many others provides a set of $k$ keypoints and the associated descriptor in $d$ dimensions (for example, in SIFT each descriptor has $d$=128 dimensions). So, in ...
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2answers
40 views

Estimate/Compute parameters of image dataset

I have a dataset of images taken by Kinect (RGB and D) How can I extract the following information only from the images: Frame rate Camera height The dataset containes images of person (s) moving ...
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1answer
29 views

Difference between texture and illumination in image

I am new in image processing. What are texture and illumination in image? How can we define these terms?
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1answer
40 views

pixels in the same image are correlated but how can I visualize it?

I am new in image processing.I know that pixels in the same image are correlated with each other but I don't know how can I draw the relationship b/w these pixels in the form of graph?.
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0answers
18 views

Edges in Content Based Image Retrieval (Java)

I have developed a programme that currently computes the standard deviation. I am trying to alter this algorithm so that it can extract the edges of an image. I have been told I can do so if I build ...
3
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1answer
60 views

Which is correct representation for function of variable?

I have a function as $$E=\int_\Omega -\log\big( p_i(x)\big) dx$$ where $p_i(x)$ is density distribution which estimated by Parzen window method. $$p_i(x)=\frac{1}{\Omega_i} \int_{\Omega_i}K_\sigma\...
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2answers
84 views

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 ...
3
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1answer
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 ...
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4answers
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?
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1answer
130 views

Removing noise from dental radiography

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 ...
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1answer
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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1answer
20 views

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 ...
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0answers
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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0answers
39 views

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 ...
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0answers
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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0answers
21 views

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 ...
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1answer
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 ...
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1answer
32 views

Add padding to object in 4-channel image

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. ...
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0answers
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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0answers
8 views

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 ...
3
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1answer
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 ...
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1answer
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 ...
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0answers
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 $m \times n$ ...
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0answers
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. ...
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2answers
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 ...
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2answers
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 ...
2
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2answers
62 views

image type after an ifft reconstruction

I reconstruct images from MRI k-space using ifft and root-sum-of-squares method. ...
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2answers
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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2answers
44 views

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, ...
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0answers
54 views

Image rotation - bilinear interpolation method

I am trying to rotate an image but I am getting unsuccessful results. I realise I can just use rotate functions in packages but I am trying to do this in a particular way so I can understand what is ...
0
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0answers
18 views

Applying window function to Gaussian Like distribution

I am trying to calculate the Modulation Transfer Function (MTF) for a CT scan. I get use the differential of multiple line profiles (as recommended by International Electro technical Commission (IEC))....