Questions tagged [image-processing]

In general, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame.

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119 views

Algorithm that Fills the White Holes Within the Character Image

I have this degraded image : Using paintbucket tool in Paint.NET Windows application, I fill the character image black. My ...
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2answers
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Binary image? Only black and white? [closed]

By name, a binary image is one that has two levels. But is it essential that those two colors are black and white? Or any other combination also allowed as shown in attached snap. Snap is output image,...
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1answer
39 views

Measure how Straight/Smooth the Borders are Rendered in an Image

I have two images: I want to measure how straight/smooth the text borders are rendered. First image is rendered perfectly straight, so it deserves a quality measure ...
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1answer
17 views

Noise problem when transforming and quantizing difference between images

I have a program which does forward and inverse DCT and quantization and dequantization using JPEG matrix. If I apply it to a single image it works fine, but if I try to apply it to a difference ...
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17 views

Bilinear Interpolation on A Subsection Of An Image

Is it possible to do bilinear interpolation on each 8 by 8 block of an image one at a time until you cover the entire image rather than doing it on the entire image? What are the consequences of this?
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What is the gradient of fft?

I have a time-series of length N generated by the following equation: ...
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23 views

Compressing sparse vectors based on compressive sensing

I have a sparse vector $x$ of size $N$x$1$ which is sparse with number of non-zeros values are $m$, it means $m$ out of $N$ values are non-zeros, the non-zeros locations are distributed randomly. ...
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22 views

security in biometrics

I read the following in one of the research papers: Cancelable biometrics using random projections can be implemented by multiplying a random matrix with a feature vector. The result is a cancelable ...
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1answer
264 views

Image watermarking in wavelet domain (data hiding in images)

I am working and researching on Image watermarking/steganography and I'm stuck at a point and want to know which technique is better in image processing for data hiding. Bit Plane Complexity ...
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2answers
854 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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1answer
22 views

What happens when you wrap a 3x3 kernel at the corners of an image?

I am puzzled by what actually happens when you process border cases when applying an image filter. For instance if I apply a 3x3 Gaussian kernel to the top left pixel[0][0], the remaining pixels that ...
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12 views

Computing White Speckle Metric in a Document Image

The paper 'Metric-based No-reference Quality Assessment of Heterogeneous Document Images', discusses about measuring the quality of characters in a document image. I'm having difficulty to understand ...
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2answers
47 views

Understanding zero-phase filters

I'm reading the book "Digital Image Processing" by Gonzalez and Woods and I'm wondering how their definition of zero-phase-shift filter is equivalent to the one given here. "Digital Image Processing" ...
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1answer
41 views

Zero-phase-shift filters must be symmetric about the origin

In reading Rafael Gonzalez Digital Image Processing, second edition, section 4.10.2, the author writes: Notch filters are the most useful of the selective filters. A notch filter rejects (or passes)...
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1answer
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Advantages and disadvantages of multiplying sparse vector with sparse matrix

Assume I have a sparse vector $x$ whose few values are non-zeros, that vector is multiplied with sparse unitary matrix $Y$ giving $z = Yx$. Are there any advantages of detecting the sparse vector $x$ ...
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2answers
223 views

How Is the Gaussian Kernel Related to the Euclidean Distance of the Neighborhoods in the Non Local Means Denoising Algorithm?

I am reading the paper A non-local algorithm for image denoising that describes the original non-local means algorithm. They define (p. 3 of the pdf) the distance between two square fixed ...
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1answer
38 views

Can Normalized Cut be used to find connected components in binary images?

I'm unsure whether Normalized Cut can or can't be used to find connected components in binary images. I would argue that it could, but could not validate this argument.
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1answer
275 views

Trying to convert Raw image(Bayer format) to jpg/png image in Python

I am using the Sony Low-light image dataset from the paper Learning-to-see-in-the-Dark. I am trying to convert Raw image (bayer pattern in arw format) into a jpg/png. I used an online tool that gives ...
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3answers
98 views

What is the DFT of a binomial filter?

I hope this question is not too simple, I just started learning digital image processing. The 1D binomial filter of size 2 is defined by $B_2 = \frac{1}{4}\begin{bmatrix}1 & 2 & 1\end{bmatrix}$...
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2answers
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How do I denoise a microscope image?

I'm working in a computer vision project, where the goal is to detect some specific parasites, but now that I have the images, I noticed that they have a watermark that specifies the microscope ...
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2answers
147 views

Fast morphological erosion/dilation with variable window sizes

I want to perform the following operation on an image: consider a square window around every pixel, find the maximum value in this window, and replace the central pixel value with this maximum value. ...
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What is Maximally Stable Extremal Regions (MSER)?

In the paper , MSER is being defined. Please help me understand what is MSER and how to implement it. The paper says, The regions are defined solely by an extremal property of the intensity ...
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2answers
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what is the difference between the convolution and differentiation over image in image processing?

In image processing the differentiation and convolution are the terms that are used interchangeably. What is the difference between applying convolution and differentiation over the image? How we ...
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Maximally Stable Extremal Regions (MSER) Implementation in Document Image Character Patch Identification

My task is to identify character patches within the document image. Consider the image below: Based from the paper titled "CG-DIQA: No-reference Document Image Quality Assessment Based on ...
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1answer
34 views

Justification for Squared $ {L}_{2} $ Data and Smoothness Term as an Error Bound

Often in variational methods (and not only) we have an energy that is of the form: $$E(u) = \frac{1}{2}\|f-u\|^2_2 + \frac{\alpha}{2}\|\psi(u)\|^2_2,$$ where the first term is referred to as the data ...
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62 views

Reconstruct signal from imprecise sampling?

I'm trying to digitize a VGA signal with a low-power consumer computer running a consumer OS and am having issues with the stability of the sampling rate. What I did so far: grabbing the green ...
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17 views

Smoothing jagged lines in an image?

I have an image like this - I would like to smoothen the lines in this (as you can see they lines are a little jaggy.) How can I do this? I obtained the lines by isolating them from another image ...
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1answer
32 views

Image Processing [closed]

I have an image and I am trying to find its rows and columns. A = imread('lena.jpg'); nrows = size(A,1) ncols = size(A,2) This is 3 dimensional matrix. Output ...
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1answer
12 views

Questions in a Character Degradation Model Paper

I have questions in the ‘Noise region definition’ and ‘Noise generation process’ of the paper “A character degradation model for grayscale ancient document images”. In Noise region definition, ...
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1answer
60 views

Licence plate enhancement

Is it possible to enhance the image below and make it more readable? I have tried apply binarization but there is some kind of shadow. So I have tried to convert image to gray scale and then ...
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1answer
2k views

What does opencv `mean` function do when passing a mask of zeros?

INTRO I am looking at this project to implement some changes. The project is written in C++ using openCV library. Its goal is to detect cars in parking area to calculate the number of free spots. It ...
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25 views

How can I stitch bottom of some image to topside of another image by erasing as much overlapped image as possible?

I have 2 images of size 1920*1080 and I want to try image-stitching on them. These are images (images are from wind turbine blade.) This is the first image And the second image. I already have ...
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2answers
30 views

Downsampling Image

Can you suggest me a good downsampling algorithm for an image. I explored area averaging method, but I am looking for better. I am using good in the sense that it should be less computational ...
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69 views

Mapping ring asteroids in Elite Dangerous by image processing

In the game Elite Dangerous, which is an online spaceflight-based sandbox game set in a procedurally-generated galaxy, one of the most profitable in-game occupations is mining commodities from ...
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What is the difference between template matching and object detection?

What is the difference between template matching and object detection? Is the only difference that the template is typically rectangular while the objects can be of any form (including rectangular)? ...
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23 views

How to know what kind of noise?

Im working with friends on a computer vision project for university. For the preprocessing part we are going to use a Gaussian filter. One of my project partner said I have to justify the use of a ...
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67 views

Is rotation of a Fourier transform the same thing as Fourier transform of a rotation?

I'm working on an image processing problem and wondering if DFT(rotation(image)) == rotation(DFT(image)) (1). My final goal is to apply rotations in the Fourier domain then do an inverse Fourier ...
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1answer
73 views

What does this notation $g(x) = S\{\delta(t) \}(x)$ mean?

What does this notation mean $g(x) = S\{\delta(t) \}(x)$ mean, where $S$ is a "system", $\delta(t)$ is the impulse function and $g(x)$ the output function of the system? I am really not familiar with ...
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3answers
417 views

Python vs Matlab? Which one better for image processing?

I want to learn practical image processing from scratch/basics in easy way. Which software will be helpful in this regard? Matlab or python?
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20 views

Gaussian filter vs median filter vs wiener filter??Noise tackling performance with image corrupted with salt and pepper noise

I am trying to remove noise in an image usig three different filters,but i am bit confused in output performance of each filter. I think gaussian filter has best performance in this case(please guide ...
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8 views

How to implement a single shot object detector with only “one” anchor box per feature-map cell

I am newbie to SSD model, I have some images of products on a shelf , I trying to detecting that products using SSD with one anchor box per feature map, please help me out, how to prepare the data and ...
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1answer
37 views

Confusions regarding meaning of “kernel” in signal processing and image processing? [duplicate]

While studying filters in DSP and DIP, the term "kernel" is often encountered What is the meaning of "kernel" in context of filters??Please kindly explain in simple words with an example I have also ...
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how formula for saturation component is working in RGB-HSI conversion?

As shown in attached snapshot,chap6 of gonzalez 3rd edition How the highlighted expression for S in eq 6.2-3 is working? and what will be range of values of S? By range,i mean,maximum and minimum ...
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86 views

which are saturation and intensity images in this figure?

The attached article talks about hue,saturation and intensity images. Where is each of them in fig6.25 ? I know that fig(b) shows Hue image but where are other two(saturation and intensity images)
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16k views

What is the difference between feature detectors and feature descriptors?

What is the difference between feature detectors and feature descriptors? Which among these are detectors and which are descriptors: Harris, SURF, Min Eigen, FAST, SIFT, BRISK
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Learn the relationship between the pixels in a chunk of an image and then search for more chunks like this one

I've just started to learn computer vision and I have a doubt about if I can do the following and how can I do it. If a 4x4 square of the image is like this one: Here I want to detect another chunk ...
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1answer
36 views

How to get the area(Pixels count) inside ring-like shape?

I have the following image, and I do like to count the pixels inside the ring to get the area. I did some morphological operations as a kind of post-processing to make the image as much as possible ...
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1answer
14k views

How to flatten the image of a label on a food jar?

I'd like to take pictures of labels on a jar of food, and be able to transform them so the label is flat, with the right and left side resized to be even with the center of the image. Ideally, I'd ...
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4answers
153 views

How to Downsample The Chrominance Components

So I am doing an image compression project for college and am trying to create a visual demonstration of how downsampling chrominance components can reduce the amount of digital information while ...
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23 views

Building a spatio-temporal filter

I want to implement a spatio-temporal filter for my images which are a set of silhouettes of a cycle of walking. So I gather all the images in an array and convolve the 3D array with my spatio-...

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