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 determine range of HSV values of the image?

Is there any method to find range of hsv values of image (object) in rectangle inside big image? I mean, there is fixed size rectangle on my image(frame from camera) and i want to find range of hsv ...
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1answer
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Equivalent 2D mask of moving-average

I have the moving-average mask as mask = [1 1 1; 1 1 1; 1 1 1]; and then I compute the convolution 3 times ...
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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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Red eye detection [closed]

Project: Red eye detection Description: I want to remove red-eye from images. I am not able to use face detector because, the faces in the images are not always frontal and also the images are of ...
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Difference between Contrast and Intensity of an Image

I wanted to generate Gray Scale wedge image of 10 Levels in MATLAB and then increase and decrease its Intensity. By high intensity, I mean mapping increasing the level of gray scale intensity in an ...
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2answers
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Sequentially get the outer contour of an Edge Image

Hi CV/Pattern Recognition Community, because my last thread was concerning the segmentation as BLOB and started to getting too big, with no clear results. I would like to reconcider the last step of ...
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Choice of Gaussian kernel parameters when lowpass filtering before image resampling?

I need to decimate a signal by a factor of q. More specifically my signal is a 3D "image": $\ I(x_i,y_j,z_k)$, which I need to downsample by a factor of two in the z direction. I want to do lowpass ...
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1answer
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Binary descriptors

I'm using an algorithm to detect interest points in an image and get their descriptor. The most recent algorithms use binary strings instead of float vectors to dramatically increase the performance ...
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2answers
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Classification of Objects from a video/Image ( human,animals,others(cars etc.,) )

Moved from here SO Link. Hi I am new to image processing field. My project is to classify the objects in an image/Video. The input is an image/video from surveillance camera. I should classify the ...
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1answer
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Best way to resample a signal (image)?

I have an original image $\ I(x_i,y_j)$ where $\ x_i = i*\Delta x, 0<= i < n_i $ and $\ y_j = j*\Delta y, 0<= j < n_j$ I am trying to implement a function that resamples the image ...
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laser speckle noise reduction

I'm trying to process an 1D signal containing a waveform of 100000 pixel. As it was acquired with a laser scanning system, and therefore it is corrupted by some annoying speckle noise. I tried to ...
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1answer
814 views

How do I resample an image to a rotated grid?

I have an image, I, sampled on a uniform grid: $\ x_i = i*\Delta x, y_j = j*\Delta y, $ I need to resample this image to a grid rotated counterclockwise by an angle $\ \theta$ around $\ (x_0,y_0)$: ...
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Is there a transformation filter to decode light signal through Glass Bricks?

A friend is doing renovations and getting his entire ground-floor street-side wall replaced with glass bricks. I told him that with all those bricks giving similar distorted views of the same room, ...
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FaceAuthentication

My project is Face Authentication. System Description: My input is only one image (which was taken when the user logins for the first time) and using that image system should authenticate whenever ...
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How to apply watershed to segment images using matlab?

How to segment this image using watershed to retrieve only the people in the image ? I have done the following so far : Calculated a gradient Calculated the watershed transform My code: ...
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533 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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1answer
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What happens when we Fast Forward the Video

I've been involved in Image Processing kind of project for the last couple of month, before which i had no experience in Image processing. While filtering the image today i had a thought what exactly ...
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Image Processing Prior to Feature Detection

I have implemented a feature detector based on Harris corners. It works fine most times, but there are cases where it performs poorly. I need to make it work on many different images without ...
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3answers
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LPF and HPF Confusion - Rectangular and Circular Cut-Offs

Interpreting some homework, I'm a little confused on what it's asking for. I'm asked to filter in the frequency domain (easy enough, just a fft2 and ifft2 when I'm done) a 256x256 8bit grayscale tiff ...
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virtually rotating the view with intrinsic and extrinsic parameter known [duplicate]

Possible Duplicate: How to get a top view using open cv? I have an image taken from an angle, at a height h from ground. I have all the intrinsic and extrinsic parameters, I need to get birds eye ...
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1answer
326 views

How can I automatically find the boundary of a high intensity region inside an image?

I have an image I(x,y): Red indicates high values and blue low values. Everything in black is drawn onto the image afterwards. The black dot (xp,yp) represents a point clicked by an user and the ...
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1answer
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How to get a top view using open cv?

I have a situation where i need to extract the top view of a road from the 'skewed' view I get from a cc camera located on some roadside tree. I would like to do this using OpenCV, but since I'm very ...
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4answers
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Resize line art image

I want to print some line drawings on A3, but they aren't very large - around 600x800px. I tried obvious functions in Gimp, like resize then enhancing with wavelet sharpener or unsharp mask, with ...
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2answers
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Precision of Computer Vision algorithms

Let's say the task is to determine element position on image. First very important thing is correct detection of object then some algorithms of calculating position are used (for examble blob analysis)...
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1answer
637 views

Difference between Gabor filter implementations

I was reading a paper and came across this: I'd like to implement this in matlab, therefore I initially searched for a premade implementation. I stumbled upon this: http://www.mathworks.com/...
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3answers
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Understanding FFT of an Image

I am having trouble identifying the frequency components of an image, Here i simply generated, 256x256 binary-image. ...
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blur PSF modeling for small stright camera movement

I am interested in reovering images affected by blur of known orientation and known span. Camera movement during capture is very small, blur span is of about 0-4px. What is the most accurate way to ...
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1answer
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Relation between histogram equalization and 'Auto Levels'

I need to enhance an image using only global linear adjustment of intensity, i.e.: $$I'=aI+b,\qquad a,b\in \mathbb{R}$$ where $I$ and $I'$ are input and output (enhanced) image. I already know how ...
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How to measure a lung nodule in a CT Scan DICOM image?

In this question, I would like to focus on intensity value of the CT Scan. First, take a look at the image below: The upper image is the original image, while the lower image is the thresholded ...
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1answer
409 views

How does auto focus in cameras work?

I am just wondering how does camera auto focus work. What kind of processing does it do on images in order to adjust the focus? Is there freely available code that detects the focus level of an image ...
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1answer
458 views

What is the role of Freqency in Digital Images [duplicate]

Possible Duplicate: What does frequency domain denote in case of images? If we look deeply into Digital Images they are purely generated by the pixels distributed in rows and coloumn and the ...
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2answers
179 views

How can I use the fourier transform of a sequence of x-ray scan images to segment it?

Sorry if this question seems to trivial, but I am a bit of a novice when it comes to signal and image processing and I need some guidance. I have a 3D stack of about 256 grey scale images, each ...
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3answers
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How to remove certain background from image?

This was the image obtained after Gabor filtering... Is there some way of removing the lines inside the image except the bright white rounded defect. Did try another orientation of gabor filter go ...
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2answers
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How does Fourier Transform manipulates image technically?

I need a little bit more explanation on technical details regarding Fourier Transform in Image Processing, mainly on the frequency aspect. I see that we can use Discrete Fourier Transform to change ...
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Finding similar pictures in a database

I have large database of pictures, about a few million. I need an algorithm to find pictures which are similar to those in the database, up to a scale factor or a crop and shift (I have only these ...
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1answer
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finding textures on images

I want to detect textures on images, for example after proccessing on image must be shown areas of each texture and area where is no texture.And I want to compute "mean" texture of selected area. ...
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1answer
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What distance metric can I use for comparing images?

I usually use the mean squared error (MSE) or peak signal-to-noise ratio (PSNR) to compare two images, but this isn't good enough. I need to find a formula that returns a very big distance between an ...
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1answer
140 views

scale invariant face similarity metric

I need some face similarity metric. I know about PCA,LDA approaches that uses raw pixels data, but they are not scale invariant(I know that I can resize image but I think that's not good solution). ...
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3answers
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Face Recognition / Image Processing

For a Face Recognition system which one is better using Neural Network or the Histogram with pattern matching concept ?? which one is more accurate?? I need to integrate the face recognition engine ...
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1answer
284 views

Convolution involving turning each pixel value to the most represented pixel value of the neighbourhood

In order to correct gradual changes of intensities in the background of grey-scales images, I have been blurring them and then subtracting the original images from the convolved one. In some cases, I ...
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3answers
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Texture Classification via DCT

How viable would it be to classify the texture of an image using features from a discrete cosine transform? Googling "texture classification dct" only finds a single academic paper on this topic, ...
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How is Weighted Thresholded Histogram Equalization different from Gamma Correction Image enhancement [duplicate]

Possible Duplicate: How is Weighted Thresholded Histogram Equalization different from Gamma Correction Image enhancement In case of Weighted Thresholded Histogram Equalization we use:- calculate,...
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1answer
710 views

How is Weighted Thresholded Histogram Equalization different from Gamma Correction Image enhancement

In case of Weighted Thresholded Histogram Equalization we use:- calculate, the Weighted Probablity Density Function for Image using, $$P_{wt}(k) = \left( \frac{P(k)-P_l}{P_u-P_l} \right)^r P_u$$ ...
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1answer
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Is an image a random variable or a random process?

Is an image a random variable, where each pixel is a realization of the same random variable? Or is an image a collection of random variables (if an image is of size mxn, there are mxn distinct random ...
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1answer
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Are all of the edge descriptors necessary to differentiate edges?

My question is about edge descriptors produced from an edge detection method applied on an object image. As we know, an edge has four descriptors edge normal, edge direction, edge position, and edge ...
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3answers
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Image Processing: How to detect a quadrialteral signboard in image?

How can I detect a quadrilateral signboard from an image captured using a mobile phone? How can i detect shapes like rectangle? rounded rectangle (rounded corners instead of shape corners)? I am ...
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1answer
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How do I implement the Structure tensor (in Matlab)?

I am trying to figure out the details on how to implement the structure tensor in Matlab and need some advice! For an image $\ I(x,y) $ the structure tensor S is given by: $$ S=\begin{pmatrix} W \...
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Plotting DNA chromatogram trace data

Sanger DNA sequencing produces a chromatogram trace which can be visualized with a number of programs, including FinchTV or ChromasLite. The raw data consists of co-ordinates for each of the four DNA ...
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how to detect center of a blurry circle with opencv

I have got the following image: There are curvs on the picture. i would like to find center of the circles containing curves. i tried opencv and hough circle transform but had no results.
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Detection of number of yarns in the fabric image

I am a novice user in image processing and working on a project to determine number of yarns in a fabric image i.e. warps and wefts (Perpendicular and parallel yarns to x-axis). I am trying to detect ...