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 compute sinc period in frequency domain and width of pulse

I have an image convoluted by a rectangular PSF of a blur kernel. The fourier transform of the PSF has pattern of a sinc function: $\frac{\tau sin(\pi \tau f)}{\pi f}$. The image size is 256x256. ...
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239 views

Evaluation of Keypoint Detector and Feature Descriptor Combos for Vehicle Detection

I am currently doing a research project into the effectiveness of different keypoint detector and feature descriptor combinations for the task of vehicle detection. At the moment I am using a SVM for ...
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Separating similiar object in an image

I have posted a question on Stackoverflow and was suggested to post here. Please refer this question for the images: Similar Question: I have used SURF Keypoints and a FLANN Based matcher and ...
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129 views

Local signal-to-noise ratio for an image

I want to do one of these common experiments to see the effect of increased noise on the performance of a feature detector. To do this add zero mean gaussian noise with fixed sigma to the image and ...
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Find branches in skeleton image using matlab

I have a skeleton image. I am able to detect branchpoints, endpoints and able to label image using BWMorph, BWLabel. Now I want to differntiate between skeleton center line and branches. In short I ...
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How to categorize the images based on Illumination / shadow?

Input: Cropped face or Non Cropped face images. Detailed explanation: My project is face authentication. I am using OpenCV face detector to crop face from images. I am using OpenCV implementation of ...
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519 views

Use fourier transform to calculate image pixelation coef in python

I want to calculate a coef of image pixelation to remove bad pictures from a bunch of files. Some pictures results from bad compression and we can see a lot of pixelation on them like img a here: ...
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How many ways are generally used for Image segmentation using Image processing?

I want to segment an image and extract very small specific area using image processing without using machine learning. Most of the time I used color based segmentation using thresholding. but it is ...
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Optical flow Horn & Schunck smoothness error

I was reading about the Horn & Schunck method and they define the smoothness error as (Robot Control 1988 (SYROCO'88): Selected Papers from the 2nd IFAC Symposium p. 348): $E_{sm} = \iint{\left(...
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Why can ARSS not recreate audio from a spectrogram without sounding muffled?

Why do ARSS and all audio to spectrogram then back to audio program's create audio files that sound muffled? I know their is some physics and math with the short-time Fourier transform and etc. I ...
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Find specific feature within an image / Neural Networks

i am working in the field of image processsing and we have a certain problem which is difficult to solve by rules-defined algorithms. Is it possible to teach a certain pattern into a neural network, ...
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urgent: MRI calculations question

I have a biomedical imaging exam tomorrow and I'm struggling quite a bit with this question below (from b-d). I was hoping someone could help answer these questions or at. I'll describe my approach to ...
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Similarity or Relation between Walsh Hadamard Transform and Slant Transform

Is there any relation between Walsh Hadamard Transform and Slant Transform? Or is there any common property or similarity?
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Response function for digital camera pixel

To help me with doing some signal processing on an image, I'd like to model how a digital camera works. The camera has a bunch of pixels. What is the relationship between the value of that pixel in ...
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29 views

Camera obstruction detection

I'd like to detect if camera view is obstructed (fully or partially) by some object (paper, hand, some device, etc). Do you know any good methods for this task? I've already experimented with: RGB ...
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How can I calculate homography from the room height and camera calibration matrix?

EDIT2: I've added an assumption that the camera calibration matrix is given. Other factors (rotation, camera pose) are still not given. I want to measure actual lengths of floor edges (blue lines in ...
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51 views

What are the limitations of Watershed Segmentation Algorithm?

I am developing an Android application using Opencv to detect objects from images. I used Canny edge detector to detect the edges and extract contours, and it's working good so far. But I need to ...
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15 views

OpenCV warpPerspective implementation

I've implemented the least squares method to find the homomorphic image to fix the rotation and projection in an image. Now I'm trying to implement the OpenCV warpPerspective method in order to "fix" ...
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Understanding SURF point-of-interest localization

I've recently read Herbert Bay's paper of SURF. From which I understand: SURF calculates a table from each image pixel's Hessian matrix's determinant, instead of SIFT's Difference-of-Gaussian table. ...
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What are the meanings of Fx, Fy, Sx and Sy in Image Processing?

I am currently reading a book titled "Learning OpenCV 3 Computer Vision in C++ with the OpenCV Library", and I come across these two equations: ...
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Once spines recognized, how do I find each individual book?

I want to make a system like the Book Spine Recognition on Youtube. So I read research paper and I built this system. According this paper, I use Hough transform, then I recognize book boundary ...
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9 views

How to warp and enlarge the center of an image?

I am trying to smoothly enlarge the center part of an image. The Skimage code that I use need an inverse map that specifies location of input pixels that will occur at the output pixel location. If I ...
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8 views

Efficient way to compute how much light is present in a scene (for camera focusing)

I'm developing somewhat of a camera app and need a way to compute how much light is present in a specific scene to know how to adjust the exposure and iso level so that the focused point will detailed ...
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How to harvest the highest amount of information from an image?

I wrote a script that detects objects, crops the part of the image where an object is located and tries to increase the quality of cropped image. The object detection runs tensorflow. To increase ...
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Images as Markov chains

I have seen literature on representing black and white images as probability distributions and then computing "distances" between them, for example, in optimal transport. I was wondering if there is ...
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Satellite imagery color normalization

Satellite images available from public sources (Google Maps, Bing, ArcGis, etc) have a common "flaw" with color balance abruptly changing in places where two different images were stitched (perhaps ...
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40 views

Sampling Theorem for images

A medical Image has a size of 8x8 inches. The sampling resolution is 5 cycles/mm. How many pixels are required? Will an image of size 256x256 be enough? I know sampling in 1D signal but cannot get ...
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Disabled parking sign detection

I would like to ask you, if you could recommend some algorithm for detection of handicapped or disabled parking sign painted on the road or on the traffic sign. I am thinking about image morphology (...
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How to separate spliced(photoshopped) part from the rest of the spliced image?

I'm working on a project to detect spliced images and want 128x128 patches at the boundaries of the forged regions. I have the authentic background image and the spliced(photoshopped) one. If I ...
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18 views

Hisotgram equalisation error, help with my code

Iam working on implenting a histogram equalisation of an image without using inbuilt functions specifcally imhist and histeq, I have, for the most part understood what do during a histogram ...
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22 views

Elimination of image blurring using noise model restoration techniques

How can the blurring be eliminated from image using the noise model restoration process techniques? To my knowledge the answer must be filter.If yes,then which filter is used?
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52 views

How to implement separable bilateral filter?

I’m trying to optimize my naively implemented O(n^2) bilateral filter for 2D images. I googled and found a lot of theoretical explanations about the separate one. However, it seems there are things ...
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31 views

Use FOV or camera deprojection to find position of pixel in world coordinates relative to my camera?

A teammate and I were discussing how best to get a 3D coordinate point (X, Y, Z) in world units from an RGB-D depth image. I'm using an intel real sense D435. From how I have researched it using the ...
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What is meant by peak value of gradient magnitude?

I am trying to write MATLAB code for the research paper entitled Echocardiography Image Enhancement Using Adaptive Fractional Order Derivatives. The two thresholds are given by a=(peak+min(Gmag))/2 ...
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What is the difference between a range filter and a low-pass filter?

A low-pass filter attenuates the high frequencies, preserving only smooth variations in the provided image. The result of an image which is low-pass filtered is an image with blurred edges (hence ...
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What is the relation between smoothing and blurring?

Is there any difference between smoothing and blurring? Are these two operations the same or do these terms refer to different operations?
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Why is correlation involved? - Axis Rescaling for a 2D axes - brightfield illumination microscopy of blood cells

for 1D axis rescaling, you use a FOV calculation len_pixel=total_magnification * len_specimen_in_pixel len_specimen_in_pixel=len_pixel/total_magnification and then to get the axes rescaled, you do ...
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What is intuitively a diffusion in the context of images?

I have heard the word "diffusion" in the context of image processing and computer vision. However, images are discrete and I associate the word "diffusion" with a continuous process. Intuitively, what ...
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PATMAX / Flexible ROI for matlab

I just googled for some hours if there is any toolbox / library for MATLAB with which you can realize something similar like PATMAX does for cognex cameras. I want to add flexible ROI for moving ...
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31 views

What is meant by labels in 'gaussian shaped labels (reference attached)'?

I am trying to understand MATLAB code and it uses a line like: ...
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36 views

Image from Inverse FFT operation is sparse

I'm trying to train a deep nerual network that takes in input, an signal in the frequency domain, and attempts to learn a mapping to another signal in the frequency domain. Basically, the input to ...
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25 views

Text detection and recognition from Image

Let say you are given this image and want to detect and recognize the digits printed on the fuses. for all CV-operations i used OpenCV 3.4.4 and Python I did already these things: Detection: 1) ...
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What is a `patch expert'?

In many facial tracking algorithms based on constrained local models (CLM), such as this one and also this one, the first step of the algorithm is to learn a 'patch expert' which learns if a proposed ...
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Seperating two (image) signals in Fourier Space / Denoising

i have a problem here which is not so easy to solve. I have a measurement system which provides me two signals: -The "contrast" channel" - this is the main channel on the object -A second channel ...
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Retro Tiled Image Palettization Algorithm?

In most cases today, image palettization consists of reducing the overall number of colors in an image to some fixed number globally. This is typically solved as a straightforward but computationally ...
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21 views

Finding Local mean value of pixels of window

I want to solve the equation (2) in the attached picture which tells the local mean value. But i don't have any idea about how to evaluate this equation using matlab code. could only guess w indicates ...
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46 views

How to calculate the variance of noise when an image is downsampled?

I have a noisy image for which I know the noise variance. (Basically I created noisy image by adding noise). Now, I'm downsampling this noisy image. How does the noise variance change? Is it possible ...
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15 views

fitting lines based on image content with python

I trained an algorithm for road semantic segmentation that gives an output like this: I want to retrieve the coordinates of the vanishing point (the top of the triangle) and to fit two lines ...
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Switching camera angle based on several images

Given a number (3 or 4) of different images of a given subject from different angles, how do I interpolate to an angle that isn't available on any of the photos? What is this technique called and is ...
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problem in selecting correct algorithm for project (RCNN)

I am doing a deep learning project in which i have to identify different models of cars. i am a bit confused for the following reason: first is what algorithm should I use. I have studied that RCNNs ...