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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135 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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6k views

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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198 views

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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523 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
279 views

ROC curve with classification problems

I am working with face anti-spoofing. For classification, the Euclidean distance measure is used. The test image vector is compared with all real image vectors , and the minimum distance is chosen (...
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2 views

Can anyone tell me the matlab code for block orthogonal matching pursuit?

have implemented BOMP according to availabe algorithm. I am getting the correct indices but not the values. HOw can I ge the exact values...PLz help me out
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31 views

Implementing rotation in frequency domain and map it back to spatial domain

Please consider the following small example: ...
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8 views

What are the Red-Black Wavelets transformation for color (RGB) images?

I am looking for Red-Black Wavelet transform implementation on internet but I am unable to find it. Or How wavelets can be used for Images. Please help if you know how wavelets can be used for images.
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16 views

How to make ground-truth image for document image binarization task?

The two images are from DIBCO (Document Image Binarization Contest). The objective is to find a solution to binarize the top image (original image) to be similar to the bottom one (ground-truth image)....
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19 views

Image processing and object detection in sales force automation

We have a specific requirement in our sales force automation product. Requirement in merchandising module There is one shelf check activity in merchandising where salesman is capturing which ...
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8 views

Logical Steps to segmenting Lung Fissure Structures

I am given the task to do the Lung Major Fissure Segmentation in a CT image to find it's position in an image. This is what a Major Fissue looks like: https://www.med-ed.virginia.edu/courses/rad/cxr/...
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need tool to identify most focussed image in a series

I have a situation where I am sent a series of photographs of hand-written documents (quite old, from 1850-s). Each photo is done just as you and I would photo a page from a book, so not a ...
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1answer
24 views

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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6 views

BRIEF feature vector random point sampling 3rd method

When using the BRIEF algorithm to generate a feature vector, 5 methods are provided for selecting 2 random points inside a feature point patch. The 3rd method is described as follows: Let consider ...
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1answer
20 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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1answer
16 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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14 views

Questions about Optical Flow implementations

I have some doubts related to some of the optical flow implementations. How to compute angular error for optical flow algorithms? I know the formula for computing, $\theta=\arccos(\vec{v}_c\cdot\vec{...
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11 views

What is the name and theory behind a basic motion filter with background update?

I am working on machine vision task. I am using openCV in Python. I need to detect motion. Best would be if I can calculate the difference between the new image and background. However, the ...
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22 views

Detect Colors in an image using opencv python

How to find different colors present in an image? Is K means clustering enough or any other simple way of doing it using opencv exist?
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36 views

Understanding Upsampling Filter in Laplacian Pyramid

For the construction of a laplacian pyramid, images are downscaled and then upscaled again. My question is what is a wise decision of the kernel mask for the upscaling task ? In more detail, lets say ...
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12 views

Kalman Filter in Vision - Constant Velocity Model - Units

Let's assume we have series of frames with a known object. I want to track the object using Kalman filter using constant velocity / acceleration models. My questions are: (i) Which model to use? CV ...
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27 views

Weight update in particle filters

For particle filtering weight update, often the transitional prior is used for the proposal density, in which case the weight update simplifies to just the likelyhood function. However, in one ...
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1answer
40 views

How do I detect the sharp edges in the following image?

I am looking to count the sharp pointy triangular things in the image. However I was unable to do so. One approach I did try was take a convex hull of the contour and then find convex defects but it ...
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1answer
26 views

Recommended approach for extracting specific edges from image?

I have several sets of images with a typical image being: and from each image, I would like to extract the top and bottom curves of the object, shown in red here: What are some possible tools I ...
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15 views

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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6 views

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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15 views

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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1answer
38 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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25 views

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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1answer
19 views

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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8 views

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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35 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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51 views

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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57 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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21 views

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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58 views

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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34 views

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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1answer
20 views

Estimate gap between two adjacent images

I have two images of a panoramic view but there is a small gap (<24 pixels) in the horizontal dimension between them. I would like to do interpolation/inpainting to fill the gap, but the exact size ...
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23 views

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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19 views

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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48 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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29 views

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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18 views

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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23 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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1answer
49 views

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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79 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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50 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 ...