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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Converting very short "motionless" video frames to single, better-resolved, images

I made a mistake with my newly bought compact camera, before a trip to Japan. Instead of taking single pictures, I ended up with a few short "MP4" video files (1 second, 2-3 frames). I could ...
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6 votes
1 answer
388 views

Detect quasi-parallel lines with spurs in a binary image

I'm looking for a way to remove quasi-parallel curves from the net, as depicted in the figure. Not only the original nets (upper row in figure) contain many spurs, but also the curves to be detected ...
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6 votes
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360 views

Analytical Expression for Convolution of Two 2D DFTs

I am trying to do an image analysis problem on some images, and I want to calculate some things in the frequency domain which are giving me problems. Say I have an (discrete) image $I(x,y)$ of size $...
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5 votes
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180 views

Residual error when setting measurement matrix in compresssive sensing

I have an issue when implementing compressive sensing to recover sparse vector. Assume I have sparse vector $x$ of length, for example, $(256,1)$. $x = [x_1,x_2,.....x_{256}]$. This vector is ...
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Approaches to Segmentation in images of water surface

this is my first question here. Therefore please help me inform me when I miss any good practice in asking questions here. Given a short video sequence of an water surface, I would like to detect if ...
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4 votes
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489 views

How to construct descriptors for irregularly shaped image patches

As hinted in this answer, Perceptual hashing is a way to ascribe comparable measures (hashes) to images (rectangular patches). The images do not need to be the same size, and can be slightly distorted,...
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4 votes
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How can I detect the tree rings?

I'm looking for the way to detect the tree rings automatically in the wood dist image. Using the matlab, I have removed the background, and binarized the image. How can I detect the white and black ...
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4 votes
1 answer
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Improving Canny Edge Detection and Contours Image Segmentation

I am working on an image segmentation project to identify playing cards on varying backgrounds. For my use case I care most that I accurately extract all the cards in the image; false-positives are ...
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4 votes
1 answer
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Image Segmentation - Comparing GrabCut Method vs. Level Set Method

Checking the literature about image segmentation, if I am not wrong, there are two main approaches: Variational approach e.g. level-set optimization in Chan-Vese Combinatorial approach e.g. using ...
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3 votes
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The difference between convolution and cross-correlation from image processing point of view

The difference between convolution and cross-correlation from a signal-analysis point of view The above question gives very good information from signal processing point of view. But what about images?...
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Improving the intuition for the 2d fourier transform

As far as I understand, the 2d fourier transform is calculated as following: ...
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Overall approach for building a footfall/age/gender counter using CCTV footage

I would like some advice to validate my approach for building a computer vision system. Design brief: Using existing CCTV cameras in a retail store, detect the footfall in the shop (count individual ...
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Reprojecting an image to another viewpoint using planar homography

I have an image rendered by a simulated camera in Unity. Using this image and the known (virtual) camera pose it corresponds to, I would like to render a new image from another viewpoint. Having read ...
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3 votes
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214 views

Combining two images with different resolutions?

I am attempting to combine two radar images, each of which is a 3-dimensional cube with a range dimension, an azimuth angle dimension, and an elevation angle dimension. One image has high azimuth ...
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3 votes
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731 views

Correct Fish Eye camera Radial Distortion and blurry effect at the image edges

There are a lot of questions regarding this topic ,but I am trying to get a more clear picture from these questions. I am trying to calibrate a fish eye camera and I am using OpenCV omnidir class ...
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How to replace color in an image without changing its texture/shades or brightness?

I want to replace color in an image from another color: For that sample image is below I want to replace color such that it becomes I know it can be easily done in Photoshop but I am looking for an ...
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Horizontal banding (flickering) due to electronic rolling shutters

It is a well-known artifact that in CMOS cameras with electronic rolling shutter, horizontal banding (flickering), i.e. brightness intensity variations, are observed when the image is recorded under ...
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3 votes
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499 views

Box filter approximations for oriented gabor filters

I'm currently working on a library to generate synthetic fingerprints using the SFinGe method (by Maltoni, Maio and Cappelli) link :http://biolab.csr.unibo.it/research.asp?organize=Activities&...
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3 votes
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662 views

Interpolating on the borders of differently-resolved images

I'm creating a three-dimensional model of the earth based on SRTM height data. The data set is pretty huge, so only a small fraction of the data is available at any given time. The height data is ...
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Why PSNR decreases for Ultrasound Images?

I am working different types of filters to remove speckle noise in ultrasound image. I have taken the below paper as my base paper and trying to reproduce the results of this paper: My Base Paper I ...
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Creating a Gaussian Pyramid

I'm trying to recreate a gassuain pyramid using the following scales: There seems to be two concepts used here: 1) When an image is halved, applying a gaussian kernel of σ will apply as 2σ. 2) When ...
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3 votes
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876 views

Any Good Image Blind Deconvolution Algorithm for Removing Camera Shake

I am working in digital image restoration field, i have images that are degraded by camera shake.. can anyone please suggest me any better non blind deconvolution algorithm. my images are similar to ...
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3 votes
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137 views

Perceptually Corresponding Error Map

Is there any better measurement of error between two images than just taking pixel value differences? The problem I am tackling is stitching images containing "sensitive" objects, such as moving ...
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blur PSF modeling for small stright camera movement

I am interested in reovering images affected by blur of known orientation and known span. Camera movement during capture is very small, blur span is of about 0-4px. What is the most accurate way to ...
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3 votes
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208 views

Blurring in anisotropic outputs

I am trying to produce ideal anisotropic diffusion outputs using the standard lena image. Using the first coefficient , the output is coming somewhat close to ideal ouput but when I increase the kappa ...
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3 votes
1 answer
474 views

How virtual ads work in stadiums?

I was looking at a technology which enables virtual advertisement on the perimeter ads in soccer. It's relatively an old technology for a few years back, but I'm surprised to see the quality of it. ...
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2 votes
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49 views

How to build the measurement matrix used for compressive sensing

I have a sparse vector $x \in \mathbb{R}^{N \times 1}$, it's real and positive, the non-zeros values are maximum $N/2$ values. It means, I have at least $N/2$ zeros values in $x$. My question, is it ...
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27 views

Implementation of Deriche filter

The Canny edge detector is expressed by the derivative of the Gaussian. Its practical implementation involves the Gaussian filter, then the Sobel filter to calculate the gradient in both directions. ...
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2 votes
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51 views

Numerical optimization method for optimal edge detector

John Canny, in his paper "A Computational Approach to Edge Detection" (PDF), finds the expression of an optimal edge detector by first using an analytical approach (Euler-Lagrange equation). ...
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2 votes
0 answers
29 views

Additional artefacts in limited angle Radon transform reconstruction using the Fourier Slice Theorem

I want to simulate the limited angle Radon transform reconstruction problem by employing the Fourier-Slice Theorem which states that $$ \mathbf{F}\left(\mathbf{R} f\right) (\theta, \sigma) = \mathbf{F}...
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2 votes
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96 views

Rolling shutter time per row on downsampled images

When working with rolling shutter images, it is common that we want to know the timestamp of each row (for example for motion interpolation). Using $T$ as frame timestamp (mid-exposure, mid-row) $T_i$ ...
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  • 141
2 votes
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Discrete Fourier Transform of 2-D Images

I'm a high school student doing an essay on the applications of the Fourier transform on signal processing, but I haven't been able to find much information when applying the discrete fourier ...
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What is the name of the filter or technique to reduce depth aliasing around object edges when working with camera depth?

I'm working with a point cloud, created by sampling a 2D camera texture and a depth map. The color is combined with the depth and is projected onto a 3D scene to create a "point cloud". The ...
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2 votes
0 answers
85 views

Compressed Sensing in DOA processing

I'm trying to apply the compressed sensing theory (CoSaMP algorithm) to the DOA estimation in FMCW ULA (made of 48 elements). In the dechirped signals processing I use a first FFT to solve the range ...
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2 votes
0 answers
64 views

Adapting Richardson Lucy (RL) Deconvolution for Shot Noise Limited Coherent Imaging

I am an experimental physicist who is collecting a series of coherent imaging of trapped gas. If you are familiar with phase contrast imaging, you may understand what I mean by coherent imaging. The ...
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2 votes
0 answers
97 views

Taylor series approximation in Harris corner detection

While watching through the computer vision lecture on interest point detection, computing $E(u,v)$ requires computing the quantity $$E(u,v) = \sum_{x,y}(I(x+u,y+v) - I(x,y))^2$$ In the lecture, $I(x+u,...
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2 votes
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520 views

How does image rotation affect the intrinsic camera parameters?

I am considering the problem of how to (manually) change camera model parameter to make it "valid" on a rotated image. This question tackles resizing, but does not consider lens distortion. ...
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2 votes
0 answers
802 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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  • 133
2 votes
0 answers
29 views

Image Restoration and Standard Forms of Second Order Cone Programming (SOCP)

I'm studying the application of SOCP methods in Image restoration And I want to understand the difference between the two formulas of SOCP and how they are related. Standard form (1) : min $f^{t}x $ ...
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2 votes
0 answers
84 views

Processing Multiple Images to Detect Moving Object in Low SNR Conditions

I am new to this forum and new to the use of Fast Fourier transforms although I can program in Python 3 a bit. I have an unusual question and am seeking some general advice on (a) whether what I am ...
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2 votes
0 answers
26 views

Array bounds check o(1) (Integral image?)

Not sure if this is the correct place to ask but I have a question about techniques for processing an array of pixels with o(1) complexity. That is to get the sum of a subset of an array but if this ...
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2 votes
0 answers
34 views

Local noise intensity in an image

Noise can be assessed in uniform regions of an image, by subtracting a lowpass-filtered version of it. Then from the histogram of intensities, a global measure can be obtained (such as the average ...
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2 votes
0 answers
429 views

How do 2D DCT basis functions interact to produce 8x8 JPEG tiles?

This section is a bit of an intro. If you want to skip directly to where the problem is explicitly outlined, skip to the bottom of this post. Please note that I'm not hip with mathematical lingo, so ...
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2 votes
0 answers
223 views

How to calculate Walsh hadamard transform for image patches of odd sizes?

I was reading this paper on optical flow, which as apart of the algorithm makes use Walsh-Hadamard transform on image patches of size 2r+1. So far, where ever I have looked, I could only find that ...
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2 votes
0 answers
716 views

How do piecewise affine transformation work?

How can piecewise affine transform be used to warp an arbitrary collection of input landmark coordinates to a corresponding set of base coordinates? Can anyone give any physical examples, the book I ...
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2 votes
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247 views

Skewed rectified aerial images

I have a series of aerial images from which I would like to get disparity maps for every consequent pair. In order to do that I do a stereo rectification. The problem is that sometimes rectified ...
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2 votes
0 answers
59 views

Mid-point of worm-like objects

I have a video of worm-like objects which move. They can move in a straight line, they can rotate in circles, they can move in a serpentine/winding/sinuous way. I need to track them. I already have ...
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2 votes
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Is it possible to calculate the optical flow magnitude for rigid motion?

For objects in 2D plane, it is pretty simple to calculate the displacement vectors using optical flow algorithms such as SLIC, LK, Färneback etc. But how it is possible to know the magnitude of the ...
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2 votes
0 answers
59 views

Determining Optic Flow - Horn and Schunck - robust/insensitive to …

Can somebody explain to me why the Horn and Schunck algorithm (probably mostly the smoothness constraint) is robust to image sequences that are quantized rather coarsely in space and/or time. (Thought ...
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2 votes
0 answers
173 views

How to use FIR with Kaiser windows for 2D image

I am trying to use FIR filter (opensource codes from iowa hills software) as low pass filter, kaiser window, to filter 2D image. Does someone can guide me that how can I do that? I am able to obtain ...
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