Questions tagged [computer-vision]

Questions about algorithms for processing and analyzing images and videos.

108 questions with no upvoted or accepted answers
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7
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0answers
2k views

Detecting the damaged regions in cars

Detecting the regions where a car has been damaged and the extent to which it has been damaged is a very interesting problem. It has potential applications in automatic auto insurance claims. ...
6
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1answer
288 views

Why is Scale Space Needed to Detect Scale Invariant Features?

I have been doing research on the SIFT (scale invariant feature transform) algorithm, and while I have repeatedly read that in order to detect image features that do not vary with respect to scales of ...
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0answers
13 views

Pattern detection by stacking convolutions

CNN use convolutions to perform many tasks. In some architecture, the first layer(s) are basic filters such as Gabor's. Many CNN work by stacking a number of convolution layers to build detectors ...
3
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0answers
33 views

Partial derivatives of bilinear Sampling

I'm going over the paper Spatial Transformer Networks (link). On section 3.3 they introduce bilinear sampling kernel (Eq. 5) $$ V_{i}^{c}=\sum_{n}^{H} \sum_{m}^{W} U_{n m}^{c} \max \left(0,1-\left|x_{...
3
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0answers
20 views

Using colors in feature detection

Is there any feature detector or extractor that uses color information? Detectors like SURF and SIFT and many others work with grayscale. How do you think, may be transform can be sued to generate a ...
3
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0answers
61 views

Calculating depth mask from different lighting

I have a object which is static, the camera is static and light source is moving. How can the depth mask be calculated ? Concept is to use - calculate height from shadow length Lets imagine a have ...
3
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0answers
18 views

impact of the single pixel in disparity

Disparity essentially means the distance of a corresponding pixel in another image ( in pixels). This is clear and understood. When I looked after how the depth is related to disparity, then I found ...
3
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1answer
171 views

Image registration using gradient descent

I have a target image $f(x,y)$ (where $x \in [0, 250]$ and $y \in [0,300]$), and a source image $g(x,y)$ I want to align $g$ to $f$ using the transformation : $$\Psi(x,y;t_x, t_y, \theta) = \begin{...
3
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0answers
100 views

How can color spaces be compared?

I am currently working on image classification methods. One group of preprocessing methods are color space transformations. While there are "traditional" color spaces like RGB (the raw data), HSV, LUV,...
3
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1answer
638 views

HandyAR finger tip detection and tracking

I am reading this paper Handy AR. As suggested I am adding certain quotes from paper to get basic idea of what is it about : Intro In this paper, we present and evaluate a method to use a user’...
2
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1answer
29 views

Matching superimposed image

We are given two grayscale images, one of which contains a large, mostly contiguous patch from the other one. The patch can be altered with noise, its levels may be stretched, etc. Here's an example ...
2
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0answers
15 views

Contrast detection implementation for blur detection in microscopic image

I am currently doing a project where I have to detect if the the microscopic images given are blurry. I tried canny edge detection but they seem to perform not so good in detecting blur. I realised ...
2
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0answers
43 views

Do image artefacts reveal the original image orientation?

An image is taken and then rotated by an arbitrary angle and cropped. Let us assume that the original image is rather meaningless and is not aligned in any way. Given the rotated image, is it ...
2
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0answers
31 views

Removing fish-eye effect

The DNG specification (page 87) describes a simple algorithm for converting a "fish-eye" photo into a regular photo (just several lines of basic geometry). The transformation is configured using six ...
2
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1answer
112 views

Do white box methods for feature extraction exist for facial recognition?

Part of something I'm working on (or rather begin working on) involves white box approaches to facial recognition. I previously worked on something for character recognition using scene segmentation ...
2
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0answers
23 views

How to find the matched SIFT features that are spatially consistent?

I have extracted DenseSIFT from the query and database image and quantized by kmeans. The challenge is to find those SIFT features that quantized to the same visual ...
2
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0answers
53 views

How the SIFT results vary by changing some parameters

I'm studying the SIFT algorithm and I have some problem understanding its operation, in particular I don't understand how the results vary according to the parameters: number of octaves, number of ...
2
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0answers
240 views

Geometric interpretations of midpoint algorithm, homogeneous linear least squares and nonlinear least squares method in 3D reconstruction?

In "Multiple View Geometry in Computer Vision" Chapter 12. Structure Computation, page 310-313, triangulation is used for point 3D reconstruction. There are three methods mentioned: Midpoint method ...
2
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0answers
95 views

Image properties given by similitude moments

What image properties are given by similitude moments? These are image moments of the form shown below: $$\eta_{pq}=\frac{\sum_x\sum_y(x-\mu_x)^p(y-\mu_y)^qI(x,y)}{(\sum_x\sum_yI(x,y))^{\frac{p+q}{2}+...
2
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0answers
657 views

Relative pose estimation using epipolar geometry: Wrong translation estimate

I am trying to use epipolar geometry concepts to estimate the relative pose of cameras between two images. I am currently using a simulator to get my camera images, so the distortion is zero and I ...
2
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0answers
48 views

Registering 3D-NIR image to thermal image and vice versa

In the past I have thought a bit about how to register a NIR-image and a thermal image and noticed that this is not trivial - one statement was that if I had the depth information for each pixel, the ...
2
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0answers
97 views

Learning Image Processing/Computer Vision

What do I need to learn dense correspondence? I am a newbie in Image processing/CV. Please help me by suggesting a kind of syllabus or show me a way to learn about Dense Matching. What are the things ...
2
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0answers
245 views

How to select a good window size in the Running Gaussian Average method for Selective Background Updating?

I have been studying the Selective Background Updating in Running Gaussian Average Method, as discussed in the Wikipedia (the Variant method). The details of the algorithm, as I understand, is as ...
1
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0answers
4 views

What is the best way to compare two images for similarity if the brightness of the second image was changed?

I calculate similarity percent between two images. Another image is the same with changed brightness. I've already tried comparing by pixel (euclidean distance for grayscale and 0/1 values), comparing ...
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0answers
14 views

How to correct distortion from stitching dual camera to estimate homography

I am trying to distort the image obtained from two cameras that generate a stitching image. Unfortunately, I do not have access to the cameras and I would like to know what could be the best way to ...
1
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0answers
12 views

Drawing a planar intersection from stereo camera

I wanted to recreate the results of this paper, where the authors draw the boundary between two parts of a building from stereo images. The authors mention that the epipole and the intersection of the ...
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0answers
28 views

Would a five color display have higher image quality than an RGB display?

We have five types of photo receptors in the eyes but computer color systems just use the three red, green and blue. Three could be motivated if rod and melanopsin sensations are just linear ...
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0answers
82 views

trouble recovering rotation and translation from essential matrix

I am having trouble recovering rotation and translation from an essential matrix. I am constructing this matrix using the following equation: \begin{equation} E = R \left[t\right]_x \end{equation} ...
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0answers
18 views

How are epipolar lines useful in computer vision?

Why do use epipolar lines and what are it's benefits in computer vision ?I am unable to find the uses of epiploar lines and how they are helpful although i am aware of epiploar geometry concepts. I ...
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0answers
31 views

3D Reconstruction from multiview calibrated camera

I have a calibrated camera whose intrinsics were calculated prior. Suppose I have multi images with the same camera. Using the first two views.I have the 1) initial reconstruction using 8 point ...
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0answers
22 views

How can I compare two faces using facial landmarks?

I'm using first_order_model for an expression transfer between an video and a static image. Part of the algorithm makes a facial comparison to get the frame in the video where the face is best ...
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0answers
21 views

What is the best algorithm for detecting the texture of a person's clothes in real-time for a mobile robot?

I am working on the human following robot. the robot extracts a feature of clothes's texture and distinguishes between the people that they stand up in front of the robot. So, the robot needs that it ...
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0answers
37 views

Image/Video deblurring

I am currently working on an algorithm that will help to improve shaken blurry images. I know there are plenty of them, such as deconvolution, that is pretty useful though I don't really know how to "...
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0answers
49 views

Why HOG angular bins have values between 0 and 180 degrees?

I have learned that HOG angular bins have values from 0 to 180 since the algorithm uses unsigned gradients. I am failing to understand why. As far as I know gradient orientation is calculated as <...
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0answers
59 views

RGBD alignment without explicit transformation between RGB and depth

I have a set of RGB-D scans of the same scene, corresponding camera poses, intrinsics and extrinsics for both color and depth cameras. RGB's resolution is 1290x960, depth's is 640x480. Depth is ...
1
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0answers
12 views

Descriptors in key-features during mapping

This question is related to this question. In SLAM-type applications the feature detectors like SIFT are used for finding keypoints in the images to be matched. The candidate keypoints are matched by ...
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0answers
41 views

Where is the epipole if one camera center is not in view of the other?

In the book multiple view geometry, the epipole is defined as follows: The epipole is the point of intersection of the line joining the camera centres (the baseline) with the image plane. ...
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0answers
15 views

Does the illumination color (red/blue/green) has any effect over the disparity map generated from a stereo image?

I have a working model that creates a disparity map using stereoscopic image processing using opencv. I am thinking of improving the disparity map by using illumination and stuck with different ...
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0answers
54 views

What is the common way to approximate contour with quad?

I'm trying to find quads on stream from my webcam. cv2.HoughLinesP sometimes returns more lines then needed. How can I approximate them to contour of exactly 4 points that fits returned result best? I'...
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0answers
56 views

Why is sparsity useful in dictionary learning?

What is the particular reason for which we use sparse matrix X in dictionary learning equation Y=DX where Y is the signal matrix, D is dictionary and X is the coefficient matrix?
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0answers
33 views

Finding the linear mapping between homogeneous coordinates of affine camera

If I have an affine camera with a projection relationship governed by: \begin{equation} \begin{bmatrix} x & y \end{bmatrix}^T = A \begin{bmatrix} X & Y & Z \end{bmatrix}^T + b \end{...
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0answers
25 views

3D registration for reconstructed surface

I use Meshroom (based on the framework AliceVision) to reconstruct a scene based on photographs (e.g. a bottle on a table in a room). The software captures the bottle, but also the table and the whole ...
1
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0answers
79 views

Algorithm to determine paths that define shape of connected rectangles

Say you have a bunch of rectangles like these: They get organized into 3 distinct final shapes like this: As you can see, there are a few "complete contours", as in here: The way you figure out the ...
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0answers
53 views

Stereo-Camera: How do Bundle Adjustment and projective ambiguity fit together?

In the book Multiple View Geometry in Computer Vision Hartley and Zisserman write that given a stereo image pair, the viewed scene can only be reconstructed under projective ambiguity, i.e. is a ...
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0answers
149 views

Transform Image Point to Azimuth and Elevation

I'm working on an object tracker where I need to report the azimuth and elevation of targets. Both values should be scaled from degrees to unsigned 32-bit integers. For now I can ignore lens ...
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0answers
54 views

How to find corresponding points between two photos when there's a repeated pattern?

Suppose that I have two photos, I1 and I2 and I want to find a set of corresponding points between the two photos to define a homography between them. There are many algorithms for this purpose, ...
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0answers
16 views

Plenoptic function meaning of dx

I'm trying to understand this paper on computer vision (http://persci.mit.edu/pub_pdfs/elements91.pdf) and it talks about building a periodic table of things we can get from the plenoptic function. It ...
1
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1answer
69 views

Comparing variable image to static image

What are Levenshtein distance algorithms, but for images? I will have one static image (the target: what it should look like) and one variable image (actual: what the user has created) For example, ...
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0answers
640 views

Backward mapping with bilinear sampler

I have some experiences with Convolutional Neural Networks before. I have a question regarding the Bilinear Sampler used in "Unsupervised Monocular Depth Estimation With Left-Right Consistency" (the ...
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0answers
66 views

Combining Computer Science and Humanities

I currently hold a bachelors in Computer science and a masters in Art History. I really want to combine the two and I know of Digital Humanities but I'm not completely aware of where Digital Humanists ...