Questions tagged [computer-vision]

Computer vision includes methods of processing, analyzing, images and high-dimensional data to form high level understanding and recognition of the scene or images.

Filter by
Sorted by
Tagged with
0
votes
1answer
142 views

Computer Vision - Does implementation of Hough Transform for lines require a loop for angle parameter?

I am trying to understand how Hough Transform is implemented in real world applications. Consider a line with equation: $y = mx + b$ In parametric form, this line can be represented using (d, $\...
0
votes
1answer
147 views

given an image and its fourier transform, find another image fft using fourier properties

I managed to solve few of those questions , but I'm not manage to answer 3 of them correctly, the question is: given an image and its fourier transform, find another image fourier transform ,using ...
4
votes
5answers
326 views

Determine when a constant signal changes to another constant value

As a novice to digital signal processing I have a scenario that probably seems trivial but I dont know the answer to. I want to detect when a signal changes but ignore noise. 255 255 255 255 255 ...
0
votes
2answers
350 views

Selecting gradient orientation for Generalized Hough Transform while scaling and rotation is present

I am using this link to study Generalized Hough Transform. I will explain it briefly. In order to detect a shape, an R-table is created for the shape with $\phi$ indicating gradient orientation for ...
2
votes
1answer
425 views

Morphology - Why does the concept of opening and closing images exist when we already have erosion and dilation?

If we consider the closing operation of an image, we first dilate the image and then erode it. So, first we expand the foreground (white pixels) and and then we take away some part of the foreground. ...
4
votes
2answers
3k views

blur detection using opencv

I'm writing a script to detect blur images using OpenCV by applying Laplacian filter and calculate the std but there is a problem the std for images that contain motion blur is very close to those ...
1
vote
0answers
35 views

Chapter 4, section 4.2.1. in Szelisky computer vision, is there a mistake?

I've already asked a similar question in mathematics exchange without getting an answer, I read a bit more and I think the question might be more suitable for the signal processing exchange. ...
1
vote
1answer
480 views

Laplacian of Gaussian Approximation and Gaussian Blur as the Solution of Heat Equation

While I was reading SIFT paper(Lowe, 2004), I came across the method that he apply "heat diffusion equation" to Gaussian function to derive that $$ \frac{∂G}{∂σ} = σ∇^2G $$ I searched Wikipedia and ...
3
votes
1answer
845 views

What Are the Differences between Super Resolution, Denoising and Deblurring?

In the fields of computer vision and image processing, what are the differences between Super Resolution, Denoising and Deblurring?
1
vote
1answer
214 views

Correlation Performed by Convolution

Background: The question here is related to images in particular and not signal/waveforms. I have been reading a lot of answers about the difference between convolution and correlation but I am stuck ...
2
votes
1answer
339 views

Automatic Image Enhancement of Images of Scanned Documents (Auto Whitening)

Dropbox have make a blog post about there automatic enhancement method for scanned document image - Fast Document Rectification and Enhancement. I followed the post and they mention a formula to make ...
0
votes
1answer
25 views

Lighting for computer vision automisation

Currently I am working on a computer vision project where we want to gather data from a composite material production environment. I have an example picture here: What I learned so far that my ...
0
votes
1answer
2k views

Scale invariant template matching

For my application I am looking for a free, fast and scale-invariant template matching algorithm. The templates can only be scaled within the scene (no skew or rotation) and the scale is unknown. ...
-1
votes
1answer
2k views

Is there a penis detection demo similar to face detection?

Tutorial for face detection: Is there a script / tutorial / demo for penis detection? These guys ran into some issues: Fairly serious question, future of internet memes is at stake. Breast / ...
1
vote
1answer
398 views

How Can PCA Be Used in Image Analysis [closed]

I am still a not how PCA can be used in image analysis and where is it is mostly used. For example how can PCA be used in order to differentiate between different faces? Can you please mention other ...
0
votes
2answers
62 views

What are some current algorithm(s) for finding if two images are copies of each other?

Could anyone enlighten me on what are the current best ways to detect if two images are the same (i.e. a copy or edited copy of each other)? What feature detection method do they use (SIFT, DWT, pixel ...
-1
votes
1answer
47 views

Best way to fill an image placed into a larger box without creating artificial edges?

If you are training a neural net for a bunch of images of different size, and you have to put them all in a same-size enclosing box for input to the neural net, what's the best way to fill the ...
1
vote
0answers
58 views

Estimating the deformation of a printed label in an image

For a university honours project, I am developing an algorithm to read the text on nutrition labels. One difficulty I have encountered is how to 'flatten' the text in images of labels that are very ...
1
vote
1answer
2k views

How to detach overlapping contours but not to remove small ones. Alternative to erosion-dilation cycle

Background: I'm trying to detect trees on a sequence of aerial images by calculating a stereo disparity for consequent pairs of images. This is how disparity looks like. White spots are trees: Next, ...
0
votes
1answer
96 views

Good Metric for Spatial Resolution

I am trying to filter crawled images with their image quality. By 'high quality' I mean high resolution, not aesthetic score or perceptual score. However I found that some images have very high pixel ...
1
vote
1answer
959 views

How Do Steerable Pyramids Work?

I'm reading a paper about texture synthesis using pyramids, and the very first section mention two methods for constructing pyramids, one is the Laplacian Pyramid (which I'm quite familiar with), the ...
2
votes
0answers
208 views

Skewed rectified aerial images

I have a series of aerial images from which I would like to get disparity maps for every consequent pair. In order to do that I do a stereo rectification. The problem is that sometimes rectified ...
1
vote
1answer
72 views

Suggest an image segmentation technique to find the paste radii?

I am new to MATLAB/Digital Image Processing. So pardon me for any typing errors or wrong use of jargon. 1) I am trying to find the paste diameters for a total of 100 images in sequence. I am posting ...
0
votes
0answers
60 views

Scan an Auditorium, Count People, and Display Open Seats

I'm looking for any recommended approaches to be able to digitally process a room full people, like an auditorium or a movie theater and output the following information: Goals: How many people are ...
1
vote
1answer
34 views

Is there a closed form solution for a temporal calibration of two different signals?

Given two signals $f_1(t),f_2(t+dt)$ where $t$ is time and $dt$ is the time delay between the two signals, is there any closed-form solution with respect to $dt$? what are the efficient global ...
0
votes
2answers
959 views

Camera measurement of heart rate - frequency bias towards 50 bpm (0.83 Hz)?

I am trying to develop a RGB camera-based non-contact measurement of heart rate using principles of remote photoplethysmography. I want to be able to measure a range of heart rates I have been looking ...
1
vote
0answers
37 views

How to produce pencil-like images by pure image processing methods?

Is it possible to reproduce the following pencil-like image by pure image processing? Notes: The original image: Fig 10 in paper http://www.cs.columbia.edu/cg/aircode/aircode-uist-2017-li-et-al.pdf ...
1
vote
0answers
34 views

What is the most reliable shape representation for the purpose of detecting humans shapes?

The requirement of the algorithm is to detect human shapes. While the standard HoG or Harr cascade can be used, I am exploring whether the human shape - which primarily includes face+neck+upper-torso ...
0
votes
1answer
127 views

What is difference between along the edge and across the edge

I am trying to implement a paper called structured tensor based image interpolation. In the paper I came across a concept called tangent direction and normal direction. What they mean is tangent ...
1
vote
2answers
3k views

Camera calibration and extrinsic parameters for perspective transformation

I'm working in a photogrammetry camera and laser application where I need to measure a displacement in a specific plane, this is a quick diagram of the setup: In order to get proper measurements I'm ...
0
votes
1answer
1k views

Block normalization of histogram of oriented gradient

I am a beginner in image processing. I have some questions regarding HOG. https://www.learnopencv.com/histogram-of-oriented-gradients/ From this website, it mentioned that each element inside the ...
1
vote
1answer
2k views

MatLab - Can not detect all lines in a “simple” image using houghlines

I try to detect all lines in an image with some common geometric figures. The obvious choice, hough of MATLAB wouldn't print out the desired results. I used the ...
0
votes
1answer
3k views

Line Detection with OpenCV and Python [closed]

Why do we get less amount of lines then desired in line detection using HoughLines tranformation from OpenCV? How could we improve this method and get all the lines appearing in the image? I would ...
4
votes
2answers
14k views

Image Shadow Removal Using OpenCV and Python

How do I remove a shadow after MOG2 background subtraction using OpenCV Python? I used all morphological operations, gaussian and median blur, thresholding. it removes noises but deep shadow is ...
1
vote
0answers
844 views

Resolution and accuracy of a stereo camera

My question is pertaining to how the parameters of a stereo camera system (focal length, base, height, pixel density) affects the accuracy as well as the resolution of depth measurement. I do not ...
0
votes
1answer
2k views

Calculating distance between two blobs in a binary image in microns

I have a monochrome CCD camera with resolution 960 X 1280 and can give up-to 15 fps I am working on python opencv. I want to track the distance between two rectangular blobs in binary images in real ...
0
votes
0answers
100 views

How to overcome effect of intensity variation in image processing?

I want to process an image for which I need the method to be robust to lighting conditions. For that the only thing I can think of is normalising intensity. I did this by dividing the image with ...
2
votes
0answers
57 views

Best focus image of stack

I am trying to find the image which has the optimum focus of a focus stack (10 images). I am able to find the best two images by using the minimum gray intensity values but now the problematic part ...
2
votes
1answer
1k views

What's the Difference Between UQI and SSIM Measures for Image Similarity / Quality?

I'm studying image quality assessment (IQA) problem and I'm currently learning about quality measures UQI and SSIM, I know UQI is a predecessor of SSIM, but they look exactly the same for me...
1
vote
0answers
201 views

OpenGL Image warping using lookup table [closed]

I am working on an Android application that slims or fatten faces by detecting face. Currently, I have achieved that by using Thin-plate spline algorithm. http://ipwithopencv.blogspot.com.tr/2010/01/...
2
votes
1answer
935 views

How is WSNR (weighted signal to noise ratio) defined?

I'm studying about comparison between images to determine quality. I've learned about MSE, SNR and PSNR, and now I'm trying to understand WSNR, which I assume is similar to SNR but with weights. I ...
0
votes
1answer
601 views

Edge detection in low contrast images

I have some images which have some objects of my interest. The objects have very low contrast w.r.t. background and I would like to detect the edges of these objects in these low-contrast images. Any ...
0
votes
1answer
42 views

How to choose good features for my machine vision application? [closed]

I am trying to create an application (with OpenCV3) that can distinguish sidewalks from streets by a real-time camera that is embedded in a glass. I have 3 question about this project: Which features ...
2
votes
1answer
3k views

Detect circles in image

I have an image that has pixelated circles in it (a cross section of wires). I want to identify the wires, their location and count them. The circles never overlap and the wires are all within a 95% ...
0
votes
1answer
91 views

How Is the Bandwidth of an Image Reduced by an Octave in Gaussian Pyramid Procedure?

Reference paper 1. For arguments sake, let's say that the maximum and minimum frequency in an image are 256Hz and 1024Hz. When I perform filtering using the gaussian function, the "bandlimit" reduces ...
1
vote
1answer
141 views

What Distance Measure Is Proper for Image Patches?

I have a bunch of image patches extracted from two images. I want to find a proper measure of similarity between each patch from first images to patches from second image. I have made vectors from ...
0
votes
1answer
454 views

Frame overlapping

I 'm reading the following article from NVIDIA which involves some audio processing a the beginning : link just here (part 3.2) I don't understand the following part : In practice, we use 520ms ...
0
votes
1answer
312 views

Pattern matching methods: Based on Area and Based on features

Good morning, I'm new to image processing and I'm currently working on a project for pattern matching and OCR more specifically. In the state of art I've found the matching process can be classified ...
0
votes
2answers
2k views

What happens when we reconstruct a signal after its Fourier transform is done and some frequencies are altered? [closed]

Since we loose time information when we take a Fourier transform, what happens if we alter a few frequencies from the transform and then reconstruct the signal, do we get the altered frequency at the ...
0
votes
1answer
25 views

Are there paper about black box testing of optic flow algorithms?

Do papers exist about comparisons of the resulting optic flow and its precision compared to the used optic flow method? I would like to find paper that dealt with this topic in some way and had ...

1 2 3
4
5
15