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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154 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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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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2answers
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Confusions regarding frame rate?

We know that when many image are shown in succession they create illusion of video But what is the minimum rate of frame/images so that still images appear as video? In this case, images/frames are ...
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1answer
22 views

change in size of an individual pixel? [duplicate]

If we want to change resolution of an image,we can achieve that by increasing or decreasing the number of pixels Is there any other way ? Can we change dimensions of an indvidual pixel,rather then ...
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2answers
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Why does this image look so bad when dithered with a certain palette?

I'm trying to write software to create a mosaic of one big image made up of a bunch of smaller images. The result is okay, but I think it would be better if I used dithering. My problem is that ...
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1answer
944 views

DCT Steganograhy

I'm trying to implement a simple steganography algorithm (similar to JSteg algorithm) for hiding data in LSB of DCT coefficients in Matlab, and I ran into a problem. a. I apply DCT. b. modify LSB ...
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How do you apply DCT steganography on an RGB image?

I am working on a DCT-based steganography program in Python and I found a working model in Github. The program, however, can only encode on one of the RGB channels. Resulting in a discolored image. ...
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2answers
377 views

JPEG steganography

Aside from Jsteg of Derek Upham, Outguess of Neils Provos, and F5 (improvement of F3 and F4) of Pfitzmann and Westfeld, What other methods can you use in information hiding in JPEG images? The ...
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2answers
39 views

Relationship between sampling and number of pixels?

In case of digital images, what is the relationship between sampling and number of pixels? For upsampling, the number of pixels increass, and for down sampling, the number of pixels decrease??
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1answer
23 views

Local Histogram Processing clarification

In Gonzales' book Digital Image Processing in the section Local Histogram Processing, he writes, for a 2D image: At each location, the histogram of the points in the neighborhood is computed and ...
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0answers
26 views

The application of sparse Fourier transform

I try to understand the concept of sparse Fourier transformation, I can summarize it according to what I understood as following: Assume we have a sparse signal $x$ of size $N$x$1$ with only $k$-non-...
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1answer
77 views

KLT vs DCT basis restriction error

I want to implement 8x8 DCT and 8x8 KLT matrices to the 8-length vectors of 256x256 Lena image (e.g. each row of image there is 32 vectors 256/8 = 32 and for all rows 256x32 = 8192). I do the eigen ...
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2answers
59 views

Significance of steps involved in flipping process of an image?

The above image on the right was obtained by following steps Multiplying the image on the left by $(-1) ^ {(x+y)}$ Computing the DFT Taking the complex conjugate of the transform Computing the ...
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1answer
33 views

In process of image zooming, Sampling rate changes or stays constant?

When we zoom an image, our sampling rate will be changed(increased) or sampling rate will not change because of zooming operation?
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0answers
52 views

3D reconstruction of moving object

I am pretty new to the field of 3D reconstruction and overwhelmed by the large amounts of different methods. I am trying to find the correct method for my use case: Setting: I have a stationary ...
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1answer
435 views

What is the relation between time, frequency, spatial and spectral domains?

What is the relation between time, frequency, spatial and spectral domains? I think that time and spatial domains are the "original" domains (e.g. if the signal is a greyscale image, then the domain ...
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3answers
5k views

Which domain used for denoising additive and multiplicative noises

I want to know what is the difference between additive noise, multiplicative noise.. In what domain these noises are handled to remove? I am interested particularly in image dataset Does different ...
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2answers
47 views

which programming language is the best for image processing? [closed]

I used matlab for my projects but wondering is there any framework similar but easier than matlab.
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2answers
54 views

signal processing vs image processing?

Originally this question was asked EE SE yesterday but then i saw a comment about DSP SE ,so i am posting my question again here ,in hope to get much better and relevant answers Link of EE question ...
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3answers
2k views

Laplacian Filter Implementation in MATLAB

I implemented a Laplacian filter for the Lena image, but I get an unexpected output. For input: I get output: I used the mask ...
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1answer
172 views

How to add additive noise to an image?

I have the following image I and I want to add additive noise using the array N below. Can you please give me a calculation example of how to achieve this? Do I have to move from image space to ...
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1answer
365 views

Programming the IDWT for image processing

I want to program the 2D inverse discrete wavelet transform (only 1 level) in the case of image processing. In the matlab website there's this diagram: now, I want to program the IDWT with haar ...
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1answer
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How can I implement Guided Random algorithm walker matrices?

My Question is related to the implementation of the paper Segmentation by retrieval with guided random walks: Application to left ventricle segmentation in MRI After careful reading of the code of the ...
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1answer
64 views

Fresnel transform over image

You can recommend the literature or tell you what the Fresnel Transform does to the image. I realized that this describes the passage of a light wave through an optical element, but I need to ...
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0answers
38 views

On the channel estimation based on vector

I have a matrix $X$ of size .i.e $(8,8)$ with $M$ columns and $N$ rows. Suppose I took it's $iFFT$ column wise resulting matrix $x$ of size $(8,8)$ too, $x = F^HX_{(:,m)}, $ ...... (1), where ...
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1answer
21 views

Relation between ppi and screen(icon) size? [closed]

We know that , generally greater the ppi, the greater the spatial resolution of an image and hence quality But why do the size of icons keeps on decreasing as we change display settings of our ...
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1answer
1k views

How does image masking work?

I am new to image processing and I am interested how image masking can be used to extract a portion of a image. Have a look at this OpenCV tutorial. In the section Application of Mask, they say that ...
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2answers
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Gabor filters for digital image processing

For the application of Gabor filters in feature-based (e.g. lines and edges in images) digital image processing, it is desired that the DC component is 0. Why is this so? What effect does it have ...
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1answer
40 views

Understanding the Threshold Process in Harris Corner and Edge Detector

I have read the paper Chris Harris , Mike Stephens - A Combined Corner and Edge Detector about the Harris Corner and Edge Detector, but I didn't understand the point that after low and high threshold ...
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0answers
23 views

Calculation of derivative projection of differential Radon matrix

I am trying to write a matlab code for finding the differential Radon Matrix. . Above are formula for Radon Transform and differential Radon Matrix . What I get is the formula for Radon Matrix <...
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1answer
676 views

3D point cloud to 2.5D graycale image (metric) [Halcon?]

I have a problem ragarding transferring a point cloud to a 2.5D metric grayscale image (gray value gives depth information). I start with a three channel image of 32bit floats with each pixel ...
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2answers
117 views

Estimating Convolution Input Under the Assumption of Sparsity and Constant Non Zero Values Using Compressive Sensing Approach

I was wondering about if there is compressive sensing algorithm to estimate the sparse vector where the number of non-zeros values and amplitude of every non-zeros value are known. For example, assume ...
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1answer
664 views

The Meaning of the Terms Isotropic and Anisotropic in the Total Variation Framework

The isotropic TV is defined as the estimation of 2-norm of gradients $\sqrt{(y_{i+1,j}-y_{i,j})^2+(y_{i,j+1}-y_{i,j})^2}$, while the anisotropic TV is defined as the estimation of 1-norm of gradients $...
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3answers
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Subpixel - what is it?

I'm studying SuperResolution techniques, and I read often "subpixel"/"subpixel registration"/"subpixel accuracy". I don't find what exactly it means; Wikipedia says that is one of the three RGB ...
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1answer
2k views

What is a good distance measure for matching SIFT descriptors depending on the distribution of their noise?

I have read some papers about distance measures like Euclidean, Manhattan or Chi-Square for matching gradient based image descriptors like those computed from the SIFT Algorithm (128-D vectors). Most ...
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1answer
38 views

Palmprint Identification - Why do we align the images before we use the Fourier Transform?

I was reading the paper PALMPRINT IDENTIFICATION BY FOURIER TRANSFORM by WENXIN LI, DAVID ZHANG and ZHUOQUN XU about identifying persons based on an image of their palm. The first step in their ...
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1answer
309 views

What are the keywords to find an algorithm that detects embossed text from a 3d model?

Currently I am doing an acadmic research about an idea which came into my mind lately. I have a 3d model and I want to extract embossed text .. anyone knows any papers? or if it is already proposed? ....
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1answer
60 views

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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2answers
36 views

confusion regarding correlation in noise?

I am reading online article about image processing at following link https://www.electronicsforu.com/electronics-projects/software-projects-ideas/image-processing-using-matlab-basic-operations-part-2-...
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1answer
94 views

Normalization of signal against reference

I am trying to figure out if there is any standard way of normalizing a sequence such as a time series against a reference sequence. I am not an expert on signal processing but I was hoping someone ...
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2answers
334 views

Image processing for eye movements

I have series of images extracted from a eye tracker video for both eyes. is there any image processing algorithm/method/technique available to find the following from those images: Horizontal eye ...
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1answer
31 views

Sizes of different image types?

What is the ordering of size following image types : RGB,grayscale, indexed image, binary image? RGB highest size?and binary lowest?
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0answers
39 views

Face temperature detection without thermal camera ( by cellphone for Covid19) [closed]

i like to know what method exist in image processing to have accurate temperature estimation of human body ( especially human face ) without tomography or thermal camera, so i asked about it at Physic ...
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1answer
48 views

Develop a simple image classification system by using Laplacian of Gaussian (LoG)

I am tring to write a simple CAD system to classify some images within two groups by using Laplacian of Gaussian (LoG). I am using scikit-image for this tasks and I want to use DNN in keras to train a ...
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0answers
12 views

Looking for a good implementation / API for the radon transformation in C/C++

I am currently working on a project about Metal artifact reduction (MAR) for CT images. I am looking for a good implementation of the radon transformation and a backtransformation, ideally filtered ...
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1answer
295 views

Brightness equalization between different images

I am dealing with a proprietary whole slide image format from 3DHistech, namely MRXS. This image is produced by scanning a glass slide biopsy. The scanner takes pictures at certain positions which ...
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1answer
147 views

Image Processing- ornament detection

So I am working on a project where we are supposed to detect and count the red and gold ornaments in the picture provided in the link below. I am having issues detecting and counting each ornament and ...
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1answer
591 views

Applying Image Filtering (Circular Convolution) in Frequency Domain

To filter an image we can: Use a 3x3, 5x5, 7x7, etc. filter, that is convolve the image and the filter in the space domain. Use a FFT on both the image and the filter, multiply them together in the ...
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1answer
44 views

Encoding YUV Color Space with Positive Numbers

I got 2 hdr rgb textures/signals. When fetched one gets bicubicly interpolated and the other bilinearly. So I was thinking I can store as YUV and store Y from each texture in the bicubic one and the ...
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1answer
40 views

Producing masks from mostly-static-background subtraction when given the background

My data set contains a number of high resolution greyscale images containing a person's face. A single image containing the background without the face is provided. The background is mostly static in ...

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