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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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Difference between 2D image resampling and 1D signal resampling

I implemented a rational resampler for 2D bitmap images by the following steps: Zero-stuff to interpolate Low-pass filter to remove high frequencies introduced by zero-stuffing Low-pass filter to ...
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Removing noisy lines from image - opencv - python

I want to process different type of image to extract actual text from noisy image .I am using open cv to do this job it is working fine but the problem is I need to set different lower threshold to ...
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What is the best way to overcome color mixing limitation?

I'm doing image processing using c++ and openCV to process color. Color mixing method (addition and subtract), when you try to do it in computer with RGB system, colors will have some value (0-255). ...
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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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In what what way is the DoG more tunable than the LoG?

I was reading through this post "What is the difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat wavelet?" and noted in Chris Luengo's answer that he mentioned that the ...
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Detecting Separate Contours on Image's Edge-Map

I've implemented the Canny edge-detection algorithm, which produces a 2D binary-map of edge/non-edge pixels (in Java, is that's of any matter). It performs the ...
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19 views

How Is Laplacian of Gaussian (LoG) Implemented as Four 1D Convolutions?

I am trying to understand the four 1D convolution operations involved in implementation of Laplacian of Gaussian(LoG). I have read this answer and I am also reading ...
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Can an untilted perspective of an object be obtained from a 2D image of a tilted object using angular transformations?

I'm trying to make a height estimation algorithm that works in tandem with a bounding box object detector. The object detector can recognise the objects in images taken at pitch/yaw angular offsets. ...
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32 views

given an image and its fourier transform, find another image fft using fourier properties

I managed to solve few of those questions , but I'm not manage to answer 3 of them correctly, the question is: given an image and its fourier transform, find another image fourier transform ,using ...
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1answer
15 views

Decoding a video signal, how to get frame output to matrix for calculations?

I'd like to use python to take a video (eventually a stream) and map each frame to an RGB array of pixels. My first thought was to use ffmpeg bindings, and in memory (if possible) convert it to png ...
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2answers
77 views

Fundamental misunderstanding of windowing

I believe I have a fundamental misunderstanding of windowing. I thought that windowing is applied to a signal with pointwise multiplication, then some sort of filtering is then done to it (say using ...
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Real time peak to peak detection- Signal Processing- Android (image) [closed]

I'm trying to do real time peak detection of a image detection, but I'm running into alot of problems. I've tried lots of methods, but nothing working well. I'm using google-vision project in Android ...
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How could I calculate Interbeat Intervals (IBI)?

I would like to understand how I could calculate interbeat intervals to determine human respiration rate. Using frame image from camera I have applyed FastICA (Indipendent component analisys) on ...
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31 views

Remove a line in image with FFT

I would like to remove vertical line from an image (an example). I took a 2D FFT and try to apply a mask to suppress the line. Nonethelesse the approch is not very efficient, because i lose an ...
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40 views

which is correct sampling frequency in a real-time image processing?- Android studio

In my Android project I'm using the front camera to detect the face and do image processing. In particular, I would like to calculate the respiration rate by detecting the face. My problem is ...
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1answer
22 views

Denoising before or after Geometric Transform?

I am working on a image which needs denoising (bilateral filter) and a geometric transformation. I am not sure in which order these filters should be applied. Personally I think it is better to use ...
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19 views

Lane marker detection on KITTI dataset

I have just started on image processing and i am looking for ways or ideas to do object detection. My ultimate objective is to segment out the static road objects such as lane markers and arrow signs. ...
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how to use generalized Hough transform for 2d boundary matching

I'm a beginner working on the pattern matching. I would like to use the generalized Hough transform(GHT) for shape matching based on the boundary of the object. for example, if I have 2d coordinate ...
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3answers
40 views

How to Classify Image Filter as Low Pass Filter (LPF) or High Pass Filter (HPF)?

I am currently reading on the topics of image filtering and convolution kernels. While the process of convolution is clear to me, I do not understand, how one arrives at the statement, that a certain ...
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27 views

Phase considerations in image filter design for precise noise removal (image in post)

I have images with systematic noise caused by the instrument in different subdomains of the image, and I'd like to design a filter to - on average - improve the quality of the images. Since the noise ...
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1answer
22 views

SIFT About Difference-of-Gaussian function extrema?

How to get formula (2) by formula(1)?
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14 views

Determination of Scale (a) and Shift (b) for Complex Morlet Wavelet Analysis

I am trying to compute the phase angle data using continuous wavelet transform from the raw thermal sequence recorded with Infrared Camera. Is there any way to select Scale (a) and Shift (b) when ...
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1answer
33 views

Image zooming with Fourier transform

I want to go from this image into this one: So basically I need to scale the white square. The authors of the paper claim that this can be done in four steps: zero-padding in real space (image is ...
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1answer
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What are the advantages and disadvantages separability of Gaussian 2D filter?

I know separability of a Gaussian filter enhances the computational complexity from $\mathcal{O}(L^2*N*M) \to \mathcal{O}((L*N*M)$. How this really reflect on my program? I suppose the number of for ...
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1answer
57 views

How to Check Separability of 2D Signal / Matrix

suppose x(n1,n2) = {1 ,n1=0,n2=0 ; 2 ,n1=1,n2=0 ; 3 ,n1=0,n2=1 ; 6 ,n1=1,n2=1 } then, how do i prove it is separable.
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Image Interpolation Using the Yule Walker Equations

I have been studying about the Yule-Walker equations for prediction of a time series data from knowledge of past values of the series. Is there any way I can use the same in an image to exploit the ...
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1answer
27 views

Identify the Type of Image Distortion (On Lena Image)

I want to understand the distortions in each of the lena images shown in the image below. I see that the first one is a blur. How can undo the blur. The second one is colored salt and pepper noise. ...
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What is the size of Kernel I should Keep when using Sobel filters for finding Vertical Gradient of Image?

I've trying to find the vertical gradient of OCT images of retina and extracting top 3% of images to create an image containing my point of interest ...
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Is signal processing used in block matching algorithms

I'm working on a custom video codec which uses the standard mean squared error to find blocks. As explained by this youtube video you choose a search area size to find a block in. Each pixel of the ...
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Do chroma signals add any information to luma in YUV?

Consider the YUV 422 picture format that I get from an image sensor. The luma (Y) carries 4 bits of grayscale information. Do the additional 2+2 bits of U+V add any additional info to the overall ...
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30 views

Perspective Transform using depth and scale information

I want to transform perspective on an input image and output image from the new perspective. I have depth map and scale information. The picture roughly demonstrates what I want to do. I have a single ...
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24 views

Facing problem in plotting histogram of DCT coefficient of an image

In digital image forensic, it is assumed that the histogram of DCT coefficients of the un-compressed natural image has the smooth histogram. However, the histogram of DCT coefficients of the ...
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Does Mutual information utilize spatial information to calculate image similarity?

To calculate images similarity based on Mutual Information (MI), histogram and join histogram is required. In the literature, there are 2 contradict opinions about MI operation. 1. MI does not utilize ...
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1answer
29 views

Selecting gradient orientation for Generalized Hough Transform while scaling and rotation is present

I am using this link to study Generalized Hough Transform. I will explain it briefly. In order to detect a shape, an R-table is created for the shape with $\phi$ indicating gradient orientation for ...
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1answer
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How would I fit a distribution to this image noise?

I have collected some noise data from a dimly lit CMOS image sensor. The distribution of pixel values is tallied below:- I'd like to be able to simulate this sensor noise. How would I fit a ...
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1answer
50 views

Morphology - Why does the concept of opening and closing images exist when we already have erosion and dilation?

If we consider the closing operation of an image, we first dilate the image and then erode it. So, first we expand the foreground (white pixels) and and then we take away some part of the foreground. ...
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1answer
52 views

How to convert DFT to DCT

I've been trying to find a fast 16 point dct2 and dct3 implementation, however I could only find it in literature expressed as mathematical equations, which honestly I couldn't understand. However I ...
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1answer
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JPEG: In image compression why are higher frequency components divided by a larger number during quantization

Once 2D FDCT has been carried out on 8x8 blocks of the image data, the coefficients are quantized. This involves use of a quantization matrix where we simply divide each FDCT coefficient by the ...
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1answer
91 views

blur detection using opencv

I'm writing a script to detect blur images using OpenCV by applying Laplacian filter and calculate the std but there is a problem the std for images that contain motion blur is very close to those ...
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32 views

Is the behaviour of the following filter plausible?

I've designed a filter based on this equation $$ E(u) = \frac{1}{2}\int_{\Omega} \left[(u-f)^2 + g(\lVert \nabla u \rVert)\right]dxdy $$ Euler-Lagrange equations in this case are (should be) given ...
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Anisotropic filter implementation wrong?

I've this implementation of the anisotropic filter: ...
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17 views

Get the angle between movement of gyroscope

I want to do 3D scanning (structure from motion) just from mobile camera and sensors. I have Arduino MPU5060 6DOF gyroscope and accelerometer. I put it behind my mobile and in start time I get the ...
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29 views

Are shadows additive

So I was thinking about the problem of shadows in images. From an image processing point of view, would you classify cast shadows in a scene as an additive phenomenon or as a multiplicative phenomenon ...
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Extracting overlapping features in an image when individual features are known

Consider this image: Which is a sum of two different sets of features: The first is a collection of overlapping squares with value of 5 and the second is a collection of overlapping squares with ...
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1answer
35 views

Automatically detect an image collage

I'm trying to automatically detect if an image is a collage vs a single photograph. I'm not too concerned with difficult cases of artistic collages. What I'm trying to solve is rectangular collages ...
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1answer
38 views

Convolution offset and factor in frequency domain

See this link. The following Convolution in Spatial domain code is written in C#. ...
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22 views

Chapter 4, section 4.2.1. in Szelisky computer vision, is there a mistake?

I've already asked a similar question in mathematics exchange without getting an answer, I read a bit more and I think the question might be more suitable for the signal processing exchange. ...
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30 views

Output of a bank of gabor filters, derive ellipses like regions

I'm trying to implement an algorithm that show how to detect wrinkles in clothes, without going to much into details this is the step that is confusing me. Assuming we have an image $I$ and a set of ...
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1answer
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How Does Mean Centering Affect the Result of Using SVD to Compress Images?

I have been learning about using the Singular Value Decomposition to find low rank approximations to matrices. I had an image which I converted to a matrix. I regarded each row of the matrix as a '...