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Questions tagged [image-processing]

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1answer
711 views

Intrinsic matrices in stereo camera calibration

Suppose I have two cameras, c1 and c2, observing the same scene. I can now Calibrate each camera independently (e.g., with MATLAB's Camera Calibration App) Calibrate both cameras simultaneously (e.g.,...
2
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1answer
68 views

Looking for Methods in Computer Vision for Distinguishing Disappearing and Fading Objects

Suppose I have a video in which there are two objects $A$ and $B$. Object $A$ appears suddenly at time $Ta1$, and then disappears suddenly at time $Ta2$. Object $B$ appears suddenly at time $Tb1$, and ...
4
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1answer
414 views

Register images containing objects with varying distance to the cameras

I'm learning about using image registration to align two images, e.g., two photographs of the same scene taken from a slightly different location. What factors influence how well we can align the ...
2
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0answers
180 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 ...
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1answer
2k views

Clustering a set of images using keypoint descriptors

I'm trying to cluster around 16000 images into ~200 clusters, using kmeans with metric as euclidean distance or cosine distance. I understand that i need to extract keypoint descriptors to compute ...
2
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1answer
34 views

Viewing images that compressed using lossless algorithms

I am just trying to understand a few minor details regarding images that are compressed with lossless algorithms such as RLE. If a bmp image is compressed using RLE, when does the decompression ...
2
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1answer
365 views

Selective Background Updating in Running Gaussian Average Method for Background Subtraction

I am studying the Running Gaussian Average Method for background subtraction. One alternative, as described in Wikipedia, also known as Selective Background Updating, is to only update the ...
3
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1answer
124 views

Multi object image segmentation methods

I want to survey the state-of-the-art in image segmentation. Is there a paper on how to segment multiple objects in an image? The segmentation papers I read, normally identify one of the many objects ...
4
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1answer
3k views

Why does a color video compress better than a black and white video?

It was asked in an exam why a color video compress better than a black and white (grayscale) video using MPEG but can't find anything explaining it. In other words, we would apparently get a better ...
2
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1answer
56 views

Why does taking a gamma value > 1 make the image darker?

If I've understood gamma correction correctly (and I probably haven't), a gamma transform to an image raises the value of the intensity level of the input pixel to the power of gamma, where gamma can ...
2
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1answer
98 views

Fundamental and essential matrices, value of intrinsic parameters

I observe a scene with two cameras, c1 and c2, that produce two images i1 and i2, respectively. What I ultimately want to do is to use information of image i1 and image2 simultaneously, e.g., for ...
2
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1answer
456 views

Getting the essential from the fundamental matrix

Is it possible to get E from F? I suppose that can't work, because then I could calculate the the extrinsic (and maybe also intrinsic?) parameters of the cameras without a calibration object of known ...
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1answer
70 views

Bringing images into alignment

I observe a scene with two cameras, c1 and c2, that produce two images i1 and i2, respectively. What I now want is to bring i1 and i2 into alignment, that is I want to know where pixel (x,y) in i1 is ...
1
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1answer
166 views

What is the reason of using Gaussian model for Background Modeling?

I am a new learner to Background Subtraction (Background Modeling) and I am reading a few previous works on how it is performed. Starting with Wikipedia (by searching "Background Subtraction"), I ...
0
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1answer
235 views

Time complexity of a vertical sweep algorithm with histogram computations

In the paper Quick Detection of Brain Tumors and Edemas: A Bounding Box Method Using Symmetry, Saha et al the authors claim that the running time of the algorithm (Matlab implementation) is $O(h)$. ...
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1answer
281 views

How to test image segmentation algorithms? [closed]

What would be an ideal environment/manner to judge the effectiveness of multiple segmentation algorithms? The goal is to determine which algorithms provide the best results for pre-clinical imaging. ...
2
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1answer
566 views

Making feature vector from Gabor filters for classification

My aim is to classify types of cars (Sedans,SUV,Hatchbacks) and earlier I was using corner features for classification but it didn't work out very well so now I am trying Gabor features. code from ...
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1answer
882 views

How do I detect and rotate a square?

I have recently written code for detecting path colors in a 2D grid and printing the corresponding path costs and it works fine for me. Here's my code; I am currently new to OpenCV and know only C++ (...
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1answer
162 views

How to identify and find navels from human pics

I have a specific question and not sure what tools I can use to finish my projects. I know this may has been well solved, but I am quite new to the image recognition and detection area and don't know ...
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1answer
6k views

The Fundamental and Essential Matrix

Could someone, in plain english, explain the distinction between the fundamental matrix and the essential matrix in multi-view computer vision? How are they different, and how can each be used in ...
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0answers
176 views

Computer vision training procedures: SVM/AdaBoost vs Neural Networks

With SVM, adaboost or similar alogrithms, image training sets must be cropped with specific constraints (keep image cropping ratio the same, have object tightly cropped, same resolution) In general, ...
2
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1answer
265 views

Can you determine rotation/camera calibration from series of images separated by pure rotation

I have a series of about 50 images, each separated by a small rotation and taken from the same camera. The images are feature-dense, and I can calculate a homography from image-to-image easily. My ...
0
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1answer
40 views

What is the exact definition of a dictionary in the concept of linear algebra and computer science?

I am reading this paper for my master thesis and trying to understand every concept in it. The following sentence confuses me as to what is the exact definition of a dictionary in this concept except ...
2
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1answer
478 views

How to Know Whether a Topic is Publishable in Computer Science

Forgive my ignorance, but I am very new to the publishing process in Computer Science. I have some research that I have done involving analyzing data formats used in web-based image processing ...
2
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1answer
773 views

How can GIF compression be lossless if the maximum # of colors is 256?

I'm reading "Computer Science Made Simple" by V. Anton Spraul, and in the chapter about Graphics, he describes GIF files as follows: A GIF file uses lossless compression to store an image with a ...
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0answers
210 views

How to identify the z-ordering of objects in a computer vision or image processing scene?

Given that there is an image with objects in it, is there any method in computer vision to determine the z-ordering of objects. For an ideal image of three circles overlapping, I can determine that it ...
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1answer
490 views

Finding approximately collinear points

my issue comes from image processing. The image below is for a better understanding of the problem. I have to detect three dots (shown in black, marked with red arrows). The other points I get from my ...
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0answers
150 views

Technique behind the way google earth overlaps polygons on top of pictures

What´s the technique behind the way google earth overlaps polygons on top of pictures(like the ones users assign to streets and houses) ? It seems to be aware of perspective, and I don´t remember ...
3
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0answers
203 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 ...
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0answers
737 views

Improving MSE as fitness function for a genetic algorithm

I am implementing an autoencoder neural network in matlab, the weights of which are being optimised by a genetic algorithm. At the moment I am working on the first layer, trying to get an improved ...
3
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2answers
349 views

How do I apply patch sized features to larger images?

I've been trying to teach myself some machine learning, and I wanted to ask what seems a simple question, but I've not been able to find any resources that explain the next step. Let's say I am doing ...
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1answer
84 views

Selecting a M.S. in CS focus [closed]

I need to pick a focus in my Masters program. The running candidates are Networking Bioinformatics Data mining Computer Image Recognition In order to avoid this becoming a discussion, I'd be ...
4
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1answer
1k views

Training and testing image sizes for classification in computer vision

When training a classifier for object detection using features extracted from images (eg HoG features), how important is it that the images used for training fed into the classifier in their natural ...
2
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1answer
387 views

Method to recognize abstract objects such as hand-drawn objects?

My research is in the area of Document Image Analysis. To be specific, the topic of my thesis is to automatically recognize and index characters in a set of hand-drawn objects, e.g. given a volume of ...
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2answers
745 views

What are all the differences between the Gibbs phenomenon artefects and JPEG artefacts?

I thought the Gibbs phenomenom is the result of Fourier analysis estimation (but was it Fourier Series estimation or can it also be Fourier Transform estimation?) JPEG uses the Discrete cosines ...
2
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1answer
117 views

Resizing and aliasing in computer science [closed]

If you resize an 1000x1000 raster image to 10x10 and resize it back to 1000x1000 is this considered to be an example of aliasing?
9
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1answer
222 views

Recognizing waterways in an aerial photo — polygons from edge detection images

I am trying to recognize waterways from aerial photographs (say from Google Maps). Local governments often have GIS data that says where the waterways (and roads, buildings etc) are, but the water ...
1
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1answer
317 views

How to compute Gabor feature vector?

I'm working on semi automatic texture segmentation using level set and gabor feature vector described by Manjunath und Ma [1]. I consider their feature representation is better than others since I can ...
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1answer
853 views

Number of different output labels in Local Binary Pattern

I'm studying about Local Binary Pattern and I'm having trouble understanding the following part about the number of output labels for binary patterns from Computer Vision using Local Binary Patterns, ...
3
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1answer
77 views

How to evaluate the accuracy of a method for the extraction of the principal lines of the palmprint

Let's assume that I've implemented a method for the extraction of the principal lines of the palmprint. For instance, let's say that I'm able to do a transformation like the following one (image from ...
2
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4answers
582 views

Environment detection - How to detect “city” versus “landscape” background environment in computer vision?

I'm searching for computer vision or machine learning algorithms/methods that are used to classify or differentiate two outdoor environments. Given an image with vehicles, I need to be able to detect ...
6
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1answer
3k views

Which algorithms are usable for heatmaps and what are their pros and cons

This is a cross post from Stack Overflow, and DSP at Stackexchange since I cannot really decide which part of Stackexchange is most fitting. If this is the wrong place please tell me and I'll remove ...
1
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1answer
93 views

Job sites for applied/interdisciplinary mathematics related to computer science? [closed]

I'm looking for job sites in applied/interdisciplinary mathematics, more specially, say postdocs or higher positions in mathematics and medical imaging, mathematics and computer vision. I'm aware of ...
3
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1answer
102 views

Environment requirement in training image dataset for classifier

I have a question about preparing the dataset of positive samples for a cascaded classifier that will be used for object detection. As positive samples, I have been given 3 sets of images: a set of ...
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2answers
2k views

Object recognition - given an image, does it contain a particular 3D object of interest?

I have in mind a particular 3D object. Given an image taken by a camera, I want to check whether that image contains an instance of my object. For instance, let's say that the object is a bathroom ...
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3answers
9k views

Shannon's entropy for an image

Shannon's entropy [plog(1/p)] for an image is a probabilistic method for comparing two pixels or a group of pixels.Suppose an image with a matrix of 3x3 has pixel intensity values ...
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1answer
2k views

Deriving the Sobel equations from derivatives

Many sites give the Sobel operators as the convolution mask for smoothing an image. However, I haven't found a single site that describes how you can derive the operators from partial first ...
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5answers
2k views

Where can a student learn image processing?

I am a student of computer science with interest in image processing. I have learned how to apply a few effects to images like making them grayscale, sketching them out of lines, etc. I would like ...
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1answer
1k views

circle packing algorithm used by Percolator

I was admiring this rendition of the Mona Lisa from quasimondo's Flickr account. He says: Combining circle packing with data visualization. The pie charts show the distribution of the dominant ...
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1answer
50 views

How can you see which points in the spectrum is from which pixel in the original image?

Take the image and spectrum below. If I look at the spectrum, it just look like noise.... How to make sense of it intuitively? Image: Frequency spectrum of image (using Fourier Transform):