# Questions tagged [image-processing]

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85 questions with no upvoted or accepted answers
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632 views

### Space filling between random 2D lines

Note that I had asked this question in GIS forum, although it has gotten many up-votes, still has not received any answer. Hope you can break the silence, some collaboration :) Consider a region (...
• 161
230 views

### Modifying the JPEG compression to use custom block patterns

recently, while watching a video about machine learning, I had an idea about creating an image compression algorithm, that works similar to JPEG, but is based on arbitrary bitmaps as blocks. I should ...
• 141
71 views

### Metrics for image/visual complexity in computer vision/graphics?

Could anyone kindly point me to revenant literature in computer vision/graphics that detail on metrics for image/visual complexity and how to regularize that? More specifically, I am trying to design ...
• 141
374 views

### Stereo images rectification and disparity: which algorithms?

I'm trying to figure out what are currently the two most efficent algorithms that permit, starting from a Left/Right pair of stereo images created using a traditional camera (so affected by some ...
62 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_{...
26 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 ...
• 131
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### Comparing pixel density and number of pixel values

I am curious about an image processing algorithm used in this code pulled from this github repo. I have posted an explanation of the code below. ...
217 views

### Simplify closed-path points without intruding into the inside of the path

I want to: Simplify a set of points that outlines a closed opaque image on a transparent background. The simplified set of points should not intrude into the closed opaque image. I use a Marching ...
• 131
656 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’...
• 131
30 views

### Algorithm to find best alignment of one curve onto another

So I've boiled a certain problem I have down to the point where I have two images of (approximately) the same scale. One which contains a closed curve, and one which is a partial curve. I want to ...
• 121
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### approximate line segments from array of unsorted points

The polygon above is actually a collection of a lot of black points closely packed together. I want to approximate these black points as straight line segments. The black points are not sorted in any ...
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44 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 "...
• 21
49 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 ...
23 views

### Evolving zero level set in images

I'm trying to implement a simple image segmentation application that accepts an initial contour and evolves it to compute a refined contour in successive iterations. I'm taking some inspiration from ...
• 121
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### 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 ...
• 121
34 views

### Ghost outlines in image segmentation

If you observe the results of many image segmentation algorithms, you can notice the occurrence of region borders where a human observer wouldn't draw one, for instance across slow gradient/textured ...
108 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 ...
• 267
104 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 ...
• 31
319 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 ...
• 157
195 views

### Compare vectors, photo mosaic

I’m trying to make a photo mosaic web application. I split the main picture in to a number of squares. I split this square up in to 9 squares. Then I calculate the mean color (RGB) of the entire ...
1 vote
24 views

### Algorithm to find most likely continuation of image over border from set of possible next images

Is there an algorithm that would fit in the following situation: I have a sub image A of a larger image, and a set of sub images B that could (but not necessarily) share border with A. Now the ...
• 111
1 vote
69 views

### Detecting thin lines in binary images

I want to find areas in a binary image that correspond to long and thin curves. In the example below, structures thinner than 3 pixels but longer than 20 pixels are highlighted. Observe that the ...
1 vote
62 views

### Details about KNN based background segmentation

I build a python script which uses OpenCV implementation of KNN Backgroud Segmentation/Remover. I know the basics of how KNN works, but not how the background segmentation works. For the MOG algorithm ...
• 111
1 vote
28 views

### What is "energy" in computer vision

I keep seeing the term "energy" used in computer vision literature, specifically when speaking about Image Segmentation. For example on this page on Graph-Cut. I'm just wondering if someone ...
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1 vote
43 views

### RGB synthesis in pixels in a computer

A pixel is contained of 3 ranges of RGB color synthesis to add colors into a tiny-square small box, as I learned (correct me if I am wrong). But, through these 3 colors admixture can we create any ...
1 vote
155 views

### Computational complexity of median filter in image processing

I found this paper http://nomis80.org/ctmf.pdf, that describes an efficient algorithm for applying a median filter to an image. Though this works for non-HDR images, I am not sure how well it scales ...
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1 vote
114 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 ...
• 111
1 vote
29 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 ...
• 111
1 vote
183 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 <...
1 vote
262 views

### Image quantization for grayscale images with alpha channel

I am looking for algorithm that quantize grayscale image that contains alpha to 4-bits (16 colors). I quite like the effect that is used in IrfanView to decrease color depth, however, I dont know the ...
• 111
1 vote
35 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 ...
1 vote
65 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?
• 123
1 vote
404 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 ...
• 111
1 vote
81 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, ...
• 111
1 vote
120 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, ...
1 vote
28 views

### Multiphase levelset Chan Vese algorithm

I am implementing the multiphase level Chan Vese algorithm. I am using IPOL document as reference (http://www.ipol.im/pub/art/2012/g-cv/article.pdf) Everything is clear for me, except the stopping ...
1 vote
935 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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1 vote
37 views

### Accept something with probability

I am reading the following paper https://pdfs.semanticscholar.org/5e86/db52119d2d691af0365cdba7bb27dc0dc303.pdf and trying to implement the tabu search algorithm they describe for image segmentation. ...
• 111
1 vote
1k views

### Measure objects length and width by picture (pixels)

I am quite new to image processing. I have experimented with opencv and tried to measure the lenght and width of an object from a picture using a reference object where I know the dimensions. See ...
• 11
1 vote
27 views

### Want to do 3D reconstruction via simple matching

I have 2 images, called left and right images. I have some matched points $[c_l,r_l]$ and $[c_r,r_r]$ in both of them (these points are in pixel coordinates). For a 3D point in the real world, they ...
• 11
1 vote
52 views

### Finding a line shape objects (bars) in video images using neural networks (instead of Hough transform)

I'm currently trying to learn about computer vision stuff and I want to try it on a simple project of real time tracking of figures of players in a foosball game while the camera can be moving a ...
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1 vote
30 views

### Should I normalize values not bigger than 1

I have a question regarding a normalization of values especially in the case of image processing features classification. What if have a series of values that will never be bigger than 1. A = 0.004 0....
1 vote
47 views

### What kind of numerical image features should I use to distinguish between the attached types of poses?

I've around $500$ binary (black and white) images, of which I attach $2$ samples. I'm working on a machine learning problem of classifying images like them. I'd like to know what image features I can ...
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1 vote
739 views

### Why are SIFT features significantly different after simply re-sizing image?

I'm new to SIFT and was surprised by how much the features changed after resizing an image. Here's the images I used for testing: Original: Resized: Cropped: After running SIFT on those 3 images, ...
1 vote
77 views

### How to detect if objects are on top of each other?

Lets say we know the co-ordinates of each object in a camera co-ordinate systems. How do we find out if some object is on top of each other? My idea is: Compare each object and point with one another....
1 vote
65 views

### Up to what extent the hypothesis of piece wise constant intensity values is valid in ocean images?

Usually, in MR images one hypothesis research communities are making is, " the spatial intensity distribution is piecewise constant and that each tissue corresponds to a unique grayscale level. Based ...
1 vote
82 views

### Gradient Direction Equation: Color Value

I've been trying to implement this paper from Boris Epshtein, Eyal Ofek, and Yonatan Wexler, the pioneers of Stroke Width Transform . On computing the gradient direction, given the equation: theta = ...
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1 vote
98 views

### Reduction of flow-shop scheduling to a real-world computing problem

Consider the following well known flow-shop problem: We are given a set of jobs $J=\{J_1,\ldots,J_n\}$ and a set of resources $R=\{R_1,\ldots,R_m\}$. Each job $J_i$ consists of a set of operations \$...
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1 vote