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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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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302 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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155 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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136 views

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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161 views

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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594 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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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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302 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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79 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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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 ...
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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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309 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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center of oblique viewed disk with known radius

I also posted this on the math stackExchange, but it also fits to this forum, so I hope it's fine to post it here as well. I'm working on an issue related to image processing that I simply cannot ...
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242 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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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
143 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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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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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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How to select the specific frame with object

I am detecting the object from the live camera through feature detection with svm , and it read every frame from camera while predicting which affect its speed , i just want that it should select the ...
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Object detection versus object recognition

I have a slight confusion differentiating between object recognition and object detection. Some people say object detection is a sub-topic of object recognition? Can someone clarify the the difference ...
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1answer
315 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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939 views

What are the various techniques for detecting Walls in the Building(Architectural) floor plan Images?

I have to process building floor plan images to extract Walls from the structure. It is trivial in case of binary images; but the images in our case are colored, and each have different color of walls....
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247 views

compression algorithm

Steganography can hide one image inside another. If we have a compression algorithm that allows us to fit the bits for two images into the size of one, can we think of a way to modify a run-length ...
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1answer
649 views

How to get the scale bar of an FFT for a 2d image

I've been analyzing some images from a transmission electron microscope, including their FFTs, and I'm not sure how to apply a scale bar to the FFT images. I have calibrations for the real space image,...
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Understanding 2D alignment using least squares

In Computer Vision Algorithms and Applications book by Richard Szeliski, the author explains 2D alignment using least squares as follows: Given a set of matched feature points ${(x_i, x_i')}$ and a ...
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Crop all written letters from single image

Above image has handwritten hindi / deavanagari letters all on a single image. Task is to Prepare a dataset from the given assignment.jpg image using image processing tools Idon't have clarity ...
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262 views

Haralick features, am I approaching this correctly?

I'm trying to personalise a custom CBIR by adding more features not only based on colour, but based on textures' features. What I don't know is if I'm approaching this well with Haralick's features. ...
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Segmentation of warped text lines

I am trying to segment warped text lines found in photos taken from a page of a book (from the camera of a smartphone). This is meant as a preprocessing step before running OCR on them. I have found ...
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2answers
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Binarization of image for varying background and foreground colors for OCR

I am trying to develop an automated OCR system for images obtained from the internet. The images mostly consist of computer generated text imposed on a background, so the OCR should produce near ...
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1answer
127 views

What do we mean by spectrum?

Consider the context of image processing and computer vision, and, in particular, discrete Fourier transform. For example, in the sentence In the Discrete Time Fourier Transform the forward ...
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1k views

How to perform a Stockwell Transform on a 2D matrix

I was looking at performing a Stockwell transform on a matrix (or an image as it has two directions - the matrix I am interested in has a spatial dimension and a time dimension, but this should make ...
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1answer
57 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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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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453 views

Segment highly packed nuclei with dotted high intensity signal inside each object

I collected high magnification images on cell nuclei and I need to segment them (red circle in the image). The edges of the nuclei are visible but inside each nuclear object there are bright spots of ...
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How to partition collagen into separate fibers?

I have a picture representing collagen fibers of a tissue: Image is binary consisting of a background (pixels with value 0) and white collagen (pixels with value 1). A zoomed in section of an image ...
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1answer
90 views

Difference Between Contrast Enhancement and Texture Enhancement in Images

I have a very basic question. I understand that contrast enhancement is exaggerating the difference between the intensity of the adjacent structures and texture in an image is the repeating geometric ...
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What is the different of Maximum Aposteriori Probability (MAP) method and image registration with reconstruction in multi image super resolution?

I am working on multi image super resolution (MISR) for thermal imaging. I have read several papers and slide about it but there are some confussions. First, I know that the basic of MISR is combining ...
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Measures of edge image continuity and connectivity

Suppose I have a scalar image $I:\mathbb{Z}_{1,m} \times \mathbb{Z}_{1,n}\rightarrow [0,1]\subset \mathbb{R}$, where $\mathbb{Z}_{1,m} = \{1,\ldots, m\}$. (For instance, computed as the (scaled) ...
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Deriving transformation from input and output images

I will preface this by saying that my undergrad signal processing course is very far back... Context: I am comparing images of global illumination (GI) passes. I want to be able to change the ...
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40 views

Non Circulant Translation Using Fourier Transform

The translation property of Fourier Transform (FT) for a two dimensional image $f$ is as $$ f(x-x_0, y - y_0) = F(u, v)e^{-j2\pi(ux_0/M+vy_0/N)} $$ Using this equation, the following code (in Matlab) ...
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Blending artifacts in OpenCV image stitching

I am using OpenCV to blend a set of pre-warped images. As input I have some 4-channel images (*.png or *.tif) from where I can extract a bgr image and an alpha mask with the region related to the ...
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1k views

Difference between Sub Sampling and Down Scaling of Images

I know that there are many ways to upscale (interpolate) an image using bilinear, bicubic, sinc... Somehow, these same algorithms can also be used to downscale an image. But when it comes to ...
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Understanding SURF Features Calculation Process

So, I was reading the paper on SURF (Bay, Ess, Tuytelaars, Van Gool: Speeded-Up Robust Features (SURF)) and I can not comprehend this paragraph below: Due to the use of box filters and integral ...
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What Is the Difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat Wavelet?

There are three techniques used in CV that seem very similar to each other, but with subtle differences: Laplacian of Gaussian: $\nabla^2\left[g(x,y,t)\ast f(x,y)\right]$ Difference of Gaussians: $ \...
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What Is Proper Paper and MATLAB Toolbox Describing and Discussing Wavelet, Ridgelet, Curvelet and Contourlet Transforms in Detail?

Question 1: Does anybody know any paper proper for getting started understanding the concept of Wavelet, Ridgelet, Curvelet and Contourlet transforms and their differences in detail? Question 2: ...
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How to Combine Low and High Frequencies of Two Images in MATLAB?

I would like to combine two images A and B in the following way: 1) I want to take a Fourier transform of both of them 2) For image A I want to apply a weighted filter, which gives more emphasis for ...
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Impact of Interpolation Types in Image Filtering (Laplacian Pyramids)

I am trying to construct Laplacian pyramids with different interpolation schemes such as bilinear, nearest neighbor, cubic and spline to observe the effect of interpolation types. I wrote a code in ...
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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 ...