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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731 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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58 views

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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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
95 views

displaying an image

The specification of a Sony mobile phone is as follows: Screen: 5.2 inch, 1080 x 1920 pixels Camera: 19 MP, 2160p first, what does the value 2160p represent? Second: multiplying 1080 x 1920 pixels ...
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How to calculate linear index of fuzziness of an image?

i am trying to calculate linear index of fuzziness of an image using this formula: i have to see a positive value according to the paper. But i see a negative value, so i think i am doing something ...
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213 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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221 views

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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49 views

Spectrogram of an executable binary [closed]

One of the approaches I have been searching so far is the application of utilizing Neural Network to classify Spectrogram images, which is heavily used in speech recognition. I am conducting an ...
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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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Fixing edge/pixel defects in image

I have a large number of images that are supposed to look something like the top part of the image: Instead, some have defects in them, as in the bottom part of the image. As you can see, there are 2 ...
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1answer
26 views

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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148 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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Could anyone explain the sliding factor and min neighbours aspect of the Viola-Jones detection?

I'm looking at code that has a scale factor of 1.1, presumably meaning it's being increased by 10%, what are the advantages of this? Secondly, I don't understand what minNeighbors actually mean and I ...
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How to find location of minimum dimension of contour using opencv?

suppose this is our input image and now we have to detect the point of minimum dimension, which I show as the red dot in an output image
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3answers
70 views

image compression versus image denoising

Wavelet based image denoising may be performed by thresholding (selecting a threshold value, and discarding all values below the threshold. Wavelet-based image compression may also be performed by a ...
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33 views

Measurement of moving objects using computer vision

I am working on a project to measure lengths of the black objects and distance between them using computer vision (Shown below in the fig.). These objects are moving on a conveyor shown in the blue ...
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1answer
38 views

Noise amplification with inverse filtering

I'm trying to gain a better (mathematical) understanding of why inverse filtering is almost never the solution for correcting an image. From what I understand, we start with a discrete signal $s[n]$ ...
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1answer
56 views

Are there any efficient algorithm to detect circular shape of arbitrary size in an image?

I have images that are 1278 by 1024. They are pictures of a certain product that is rectangular in shape and are about 25mm by 20mm. As a part of a quality inspection process using computer vision, ...
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How to plot histogram of difference of two images using MATLAB

i would like to calculate difference of two images. Then, histogram of difference of two images. So I can plot a histogram but I am not sure whether it is true or not? Also, I am not sure about what ...
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20 views

How to improve interpolation for chroma upsampling (4:2:0 to 4:4:4)?

I am trying to perform the best possible interpolation in order to perform proper chroma upsampling from 4:2:0 YCbCr to 4:4:4 YCbCr. I have implemented the improved interpolation proposed at this ...
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57 views

image resolution in smartphones and laptop [closed]

If I used a smartphone with high pixel per inch (ppi) value for capturing an image with certain dimensions, what happened if this image is displayed on a laptop (larger screen) with: the same ppi ...
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How to choose the most appropriate color space for a computer vision application?

A lot of image processing techniques used in computer vision consist (among other things) in switching from RGB to another color space (HSV, YUV, LMS...) : color transfer, visual tracking... It seems ...
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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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1answer
131 views

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 '...
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2answers
464 views

Detecting the rotation of digits in an image

I am trying to find the rotation of a given set of digits from the image. For example: There is no additional background information, only the digits are given in the input. I have tried using ...
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1answer
413 views

Binarization, and then thinning/skeletonization

I have pictures of networks, like the one below, and my goal is to obtain the network's skeleton from processing those images. My approach lies in two steps, first I convert grayscale image to binary ...
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1answer
45 views

How to recognize for small video sequence with a large sequence?

I'm working on the idea of recognizing a small video sequence (a sequence of 18 seconds) within a long one (a sequence of 15 minutes), the first idea that come to mind stats that I have to ...
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1answer
142 views

Intuition behind image derivative using Fourier Transform for edges detection

This equation can be shown mathematically: $\frac{\partial f}{\partial x}=\frac{2\pi i}{N} \mathcal F^{-1}\left(u\cdot \mathcal F(f(x,y)\right)$ I am struggling to understand the intuition behind it ...
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2answers
91 views

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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3answers
255 views

Would capturing an image at 640x480 then resizing it to 1280x720 improve the ability to detect/resolve objects in the image?

I work in a research lab and am currently setting up a system to image objects approximately 30 microns in diameter with a 250x USB microscope, then use image subtraction to isolate the objects as ...
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23 views

What is the difference between positive matrix coefficients and negative matrix coefficients of an audio?

I have turned an audio file into an one dimensional array by using audioread function in matlab and found several positive and negative fractional coefficient values.What is the basic difference of ...
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1answer
69 views

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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2answers
52 views

Image resizing and interpolation

In digital image processing, I need to understand what does image resizing do? Does it only change the dimensions of the image, for example, from 256×256 to 128×128 with the same pixel spacing (the ...
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1answer
84 views

What Is a Weighted Local Histogram?

I'm reading through a couple of academic papers, and this terms often comes up "local weighted histogram". An example of quote is the following: First, cumulative histograms are built for every ...
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1answer
167 views

Homography Matrix Correlations

If the homography matrix of Image 1 to Image 2 is given, and another homography matrix for image 2 to image 3 is given, how do I calculate the homography matrix for image 1 to image 3? PS : I need the ...
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291 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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1answer
111 views

What motion estimation techniques that could estimate the motion of every pixel?

I'm trying to estimate a motion from a video, however based on my finding, those methods usually meant for large motion and sparse in nature. Optical flow: Sparse and fail to detect sub-pixel motion ...
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2answers
32 views

Confusion regarding lacunarity of koch curves with same fractal dimension but different orders

I'm trying to use the concept of lacunarity to classify images, as per how a few research papers have done it. To verify whether my equations and implementation are correct, I'm trying to verify the ...
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384 views

Deconvolution Question on Article “Deriving Intrinsic Images from Image Sequences” by Yair Weiss

there are n derivative filters: $f_i$, and denote $f_i^r$ as $f_i$'s reverse filter such that $$f_i(x,y)=f_i^r(-x, -y)$$ $r_i, f_i$ given, to find $r$ from the equations: $$f_i * r = r_i, (1 \leq i \...
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335 views

Question About Linear and Circular Convolution - 1D and 2D

We know that applying a filter on an image is called correlation or convolution depending on the filter angle. In Gonzalez I have read that we can apply linear convolution on an image. Here I have a ...
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Best way of segmenting veins in leaves?

I have done a lot of research and found out methods like adaptive thresholding , watershed etc that can be used of detecting veins in leaves . However thresholding isn't good as it introduces a lot of ...
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1answer
2k views

Improving Template Matching Algorithm for OpenCV

Car detection using OpenCV I am working on a small personal project where i have to know wether an image shown is a car or not. I am using the basic OpenCV python based template matching. Positive ...
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1answer
153 views

Obtaining the size of objects from an image

My objective is to be able to obtain the size, in pixels, of objects in images I'm receiving from a camera. I've tried two approaches thus far, both working to some extent, and I'm wondering if there'...
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26 views

Infrared image dataset for enhancement?

I'm working on near infrared image enhancement. I'm searching for low-contrast images. Example image is below.
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770 views

Calculating the SNR of a blurred image

I have a blurred and noisy image $X$, I want to apply the Wiener filter on it and get a deblurred and denoised image $Y$ (i.e apply inverse of blurring filter while at the same time reducing some ...
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1answer
1k views

Finding circle in binary image (R, not matlab)

How would I go about extracting the circular area of a binary image which looks like: The two rods emerging from the side of the circle are noise. I know of the hough transform in Matlab. However, I ...
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208 views

2D DWT computation order

In 2D the discrete wavelet transform (DWT) of an image using lifting based 5/3 filter, if I perform a row-wise operation first then perform column-wise operation then I will get 4 sub-band LL, LH and ...

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