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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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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Face image quality assessment

I'm trying to filter out bad face images (with artifacts) generated by StyleGAN. Is there a good image quality measurement mechanism in python for doing this? I've tried using BRISQUE but it is not ...
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How to Extract High Frequency and Low Frequency Component Using Bilateral Filter?

What does High frequency and low frequency component signify in an image. How to separate out the high frequency as well as low frequency component of an image using Bilateral filter.
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Which Approach Is Better for Decomposing an Image into High Frequency and Low Frequency Components?

Which approach is better or there is mathematical justification for using Bilater filter and Fourier Transform to decompose a image into High Frequency and Low Frequency Component. Both Bilateral ...
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How to sharpen hair strands in an image?

I have an image like this: I am trying to build a semantic segmentation and matting model which currently gives an output like this: One can see that some regions between the hair strands are fuzzy....
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image processing vs Computer vision?

I have already tried searching about subject and the only one thing I could understand is that computer vision involves object recognition but image processing does not involve object recognition ...
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How are line pairs and pixels related in image resolution?

I hope this is the correct place to ask this. If not, please refer me to a better place, thanks. Now to my question, I am learning about digital image processing, and the book I am reading is ...
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What does structure matrix do

can anybody explain to me what does structure matrix exactly do in image processing? What happens to the pixels? By structure matrix I mean: $$S_w[p] = \begin{pmatrix} \sum_{r}w(r)[I_x(p-r)]^2 & ...
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DC Coefficient of JPEG Block

Suppose I take a grayscale image and break it into 8x8 pixel blocks, then take the DCT of those blocks. What is the DC coefficient of the block in relation to the whole image? To simplify I'm ...
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How do I filter out this horizon from my contour?

I am trying to identify the T-rex and obstacles (cactus and bird) from Google's no-internet game. What I have done is: Apply GaussianBlur filter Apply Canny Apply Dilate Apply erode findContours ...
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Why do we use the HSV colour space so often in vision and image processing?

I see the HSV colour space used all over the place: for tracking, human detection, etc... I'm wondering, why? What is it about this colour space that makes it better than using RGB?
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Labview vs Matlab? Which one better for image processing?

I want to learn practical image processing from scratch/basics. Which software will be helpful in this regard? Matlab or Labview?
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How do you save/convert an image to be in the frequency domain?

Quick Note: I don't believe this is a subjective question... however if it is I will gladly modify to be more objective In ImageJ, if I take the FFT of an image, how can I save this new frequency ...
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Question about image equalization

Let $f$ be an $N \times M$-image and suppose that $g$ is its equalization. Question - Why the equalization does not change the objects, why a car on $f$ does not convert into a bus on $g$?. It is ...
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What is the meaning of the length of diagonal lines in FFT

I am relatively new to FFT analysis of images and have a question about them. I like to think I understand the basics but many of the properties shown in a FFT image are beyond me. My main question ...
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What is meant by 'combine the luminance and chrominance '

I am new with image processing. I'm trying to implement a research paper in MATLAB. I didn't understand a sentence. Here it is: The luminance is enhanced by applying the proposed algorithm and it ...
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Introduction to IP : Laplacian of Gaussian?

I am very new to the concept of computer vision (and image processing), and trying to understand the algorithm used for edge detection. One thing I'm currently struggling to figure out is the ...
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Understanding the resulting image matrix when differentiating image

Let $A$ be a image matrix and let $P(i,j)$ be the gray level of pixel $i,j$. Let $0$ be black and $255$ be white Assume I want to differentiate this image with respect to the columns $(x)$ as in I ...
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Different images between MATLAB and ImageMagick

I'm using ImageMagick 7.0.8-64 Q16 for Windows and MATLAB R2019. I'm doing the same operation (resizing with bicubic interpolation method) in both programs. ImageMagick code: ...
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Easy way to get rid of noise in a hand drawing

I would like to take a user's hand drawn input, and filter out "noise", aka small sketches or blobs, where the user might have screwed up and accidentally touched his hand to the drawing device, or ...
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Detecting enclosed regions in an image

I am having a difficult time searching for this, and I am not sure if it has a general solution, but I thought I would ask. Basically, I am looking to detect the inside of a bounded region, but ...
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what is the difference between YUV format and HSV format?

i wonder why HSV and YUV are different formats, even though they both works similarly (based on the brightness), if not what is the difference and i have confusions with YPbPr and YCbCr , can anyone ...
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What algorithm generates these “bucket coloring” artifacts?

Context: This is picture (taken with a smartphone*) of a copy of school test. The original answers were in black pencil and the professor made check marks in red. However, the parts of the answer ...
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Is it possible to read raw voltage values from an iphone CMOS sensor?

I am not an iOS developer, and I'm not sure this is the right place to ask this question, but I was curious whether using the developer sdk (or other means) it is possible to read voltage from the ...
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DSP or signal/image/data processing jokes

Some other StackExchange/StackOverflow sites are entertained with a certain level of humor or fun. What is your favorite “data analysis” cartoon? is particularly worth mentioning (IMHO) this xkcd ...
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Is It Possible to Reconstruct the Original Image from Laplacian Pyramid?

In our computer vision course, my professor said we can reconstruct the original image from the Laplacian pyramid. It just feels to me that information is lost after doing subsampling and upsampling. ...
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How to Cluster Image Colors Using K Means Clustering in CIE a*b Domain?

I am working on building detection from aerial images using Image Processing in MATLAB. I am doing an image segmentation based on the local homogeneity of image. I want to apply K Means Clustering in ...
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Efficient image matching technique for small match library set

Background A scene captured from video frames from an Android mobile device camera are to be analyzed in real-time. The scene will contain up to 12 distinct photos. The library images to be matched ...
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Anisotropic Diffusion Filter - Intuition Behind Parameters

I need to know what is iteration and divergence in anisotropic diffusion filter technique. Isotropic diffusion $$\frac{\partial I(x, y, z)}{\partial t}={\rm div}\left[c\cdot \nabla I\left(x, y, ...
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Set of all images with a certain MSE between themselves and a given image

Mean squared error between two $M\times N$ images, $I[m, n]$ and $D[m, n]$ is defined as: $$ MSE(I, D) = \frac{1}{M\times N}\displaystyle \sum_{m=1}^{M}\sum_{n=1}^{N}(I[m, n]-D[m, n])^2 $$ For a given ...
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Image Processing Perspective Transform

This youtube video shows the current world record for smb1 speedrun, but it is recorded from a phone on a CRT TV. https://www.youtube.com/watch?v=IuVLtaB8uQk Is it possible through perspective ...
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Can “Frame Difference Method' be apllied for ”Motion Detection Based Anti-Theft Project"?

I am new with image processing. I will start to a project named "Motion Detection Based Anti-Theft Project" as i said. I have to use MATLAB and STM32F4 microcontroller in this project. I don't want to ...
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Why is second-order Gaussian called Laplacian Gaussian?

We usually use Laplacian of Gaussian as the filter for edge detection or blob detection. But the filter itself is essentially a second order Gaussian. So why do we call it Laplacian of Gaussian? Is ...
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The Kernel in the Guided Image Filter

I am trying to understand how to calculate kernel matrix for guided image filter. Following is the formula for kernel calculation. where k is window withing pixels i and j belong i assumed that ...
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PSNR calculation with float arrays

The PSNR definition provided by wikipedia is often quoted in discussions regarding PSNR and other similarity metrics. Essentially the PSNR calculation has two components: the mean squared error and ...
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How is the Gaussian kernel related to the Euclidean distance of the neighbourhoods in the non-local means 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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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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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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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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301 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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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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153 views

Redistributing Color in a RGB Image According to a Gaussian Distribution

I haven't done this stuff in a while. If I have an image $I$ I can equalize the histogram of the image using some opencv procedure, it's already defined. Equalizing an histogram means essentially to ...
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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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wavelength / RGB valve per pixel

Preamble: I want to stress that I don't know anything about photo-editing or signal processing. But I am a composer who happens to be working on a project in which sound / light overlap. Question: Am ...
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Sum of Squared Intensity Difference for block matching with ORB features, c++

I am trying to implement feature matching algorithm between image reference and image current. The pipeline is as follows: ...
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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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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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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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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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How to count the number of threads in a bolt or nut using image processing?

How can I count the number of threads in a Nut with image processing? I know that I need to find the place of threads and count them. Ok, But how can I find the place of threads? This is a sample ...