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3
votes
1answer
88 views

Reconstructing a screen of permuted pixels

Reconstructing a screen of permuted pixels Summary Given a video with the pixel locations randomly permuted (once, for the entire video), can we (efficiently) reconstruct the original picture? Let: ...
3
votes
2answers
34 views

Which algorithm for counting the occurrences of a certain pattern (spots) in an image?

The Problem : Finding the number of occurrences of a certain pattern (or shape) in an image. In my example, the problem is about finding the number of spots (in variety of sizes) in an image. See ...
2
votes
1answer
18 views

High Dimensional Spaces for Images

Can anyone explain why pictures are not considered 2D, but rather high dimensional? Especially with regards to CV and AI.
1
vote
1answer
22 views

Register images from a camera which has undergone pure forward translation

Images are taken by a DSLR camera, always set at a particular Focal length. The scene contains objects with varying distance to the cameras. Since the camera has undergone translation, homography no ...
3
votes
1answer
19 views

Does JPEG compression use a heuristic model similar to MP3?

I know that MP3 uses a compression heuristic that allows it to exclude storing frequency data outside a certain range due to the limits of human hearing. Does JPEG employ some sort of non-linear ...
5
votes
1answer
41 views

perspective transformation of a grid

A perspective transformation of a point is defined as follows: $ x' = \frac{M_{11}x + M_{12}y +M_{13}}{M_{31}x + M_{32}y +M_{33}} $ $ y' = \frac{M_{21}x + M_{22}y +M_{23}}{M_{31}x + M_{32}y +M_{33}} ...
1
vote
0answers
23 views

Algorithms to convert 2D videos to 3D ones

Are there published algorithms that can convert 2D videos to 3D ones? If there are few published algorithms for this I am also interested to know how the conversion quality is.
3
votes
1answer
22 views

What is a visual bag of words and how is it implemented?

I'm currently working on implementing a bag of visual words in Python. I get the general gist of how it works but I can't seem to find any sources that explain it in more detail to a level where I can ...
3
votes
2answers
33 views

Meaning of topological distance between 2 pixels

I came across the notion of topology and topological distance in the context of image processing several times (especially when it came to mathematical morphology). I looked for a not too abstract ...
0
votes
0answers
28 views

Belief Propagation in Computer Vision

I am working on dense matching using DSP algorithm. They have used belief propagation to optimize their energy function? How do we do it? I mean how do we assign prior belief? Link: Deformable Spatial ...
1
vote
2answers
35 views

Reconstruction of drawing sequence from video

I have a video that record the drawing sequence with a pencil by a painter. I want to reconstruction the sequence from the video. And I have google some keywords like "drawing sequence ...
5
votes
1answer
29 views

Inverting radial distortion

I'm trying to understand the math behind correcting a radial distortion (caused by a lens), but I'm failing to have it explained in simple terms. I found several examples that proceed this way: a ...
0
votes
1answer
52 views

Does the SIFT feature be calculated in the original image or the corresponding octave(s)?

Given there are 4 octaves(the 1st octave is the original image, the 2nd octave is half size of the original image, and so on.), does SIFT calculate the keypoint's orientation in the original image ...
1
vote
0answers
23 views

Branch clustering for an MST

I am working in image segmentation with super pixels. My data is a large matrix describing various attributes of each stick of pixels (such as height, width and disparity). The data comes from an ...
3
votes
0answers
44 views

Removing common background in image processing phase for classification

I'm trying to build a machine learning classifier that can detect which object is in an image. I have a labled training set of images and am currently in the image processing phase. Each of these ...
1
vote
1answer
36 views

how to binarize an image?

I don't want to binarize a certain image through another program, I want to know how to binarize things myself. All I know is that there is something to do with a threshold and if it is above the ...
2
votes
1answer
16 views

Are there any articles or software which can infer original shapes from overlapping shapes?

Given that some shapes overlap in an image, are there any papers or articles or code which can infer the original shapes from the overlapping? I am thinking to apply some machine learning to this ...
3
votes
1answer
39 views

Fill in objects that pop out from background?

I need some help with a program that will fill in objects that pop out from the background. For example I have this picture and would like to get an output like this. I don't know how to do this ...
2
votes
0answers
29 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 ...
1
vote
0answers
34 views

How to train a Conditional Random Field/Markov Random Field Model for Object Classification in images given the features?

I want to classify superpixels in a image using a Markov Random Field/ Conditional Random Field model but have found no place that can help me with this (references don't even show how the network is ...
3
votes
1answer
42 views

Image Comparison tuned to Human Perception

Say I have two systems that take the same drawing commands and starts drawing on their respective platforms (i.e. HTML Canvas). After this is done, I want to save and compare these two images to ...
1
vote
0answers
16 views

Sources on dictionary learning and related algorithms

In the context of signal processing and sparse representation of signals, there is a topic called dictionary learning which is basically about how to's of the selection of basis functions used for ...
1
vote
1answer
61 views

What is the appropriate means of bias field in image processing?

I want to do image segmentation. in an article about A Level Set Method for Image Segmentation I saw that the outer use bias field estimation. I searched a lot but I couldn't understand the meaning of ...
2
votes
1answer
36 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 ...
2
votes
0answers
43 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 ...
4
votes
1answer
76 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
votes
1answer
29 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 ...
0
votes
1answer
87 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
votes
1answer
61 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
votes
1answer
44 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 ...
1
vote
1answer
110 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 ...
3
votes
1answer
341 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
votes
1answer
39 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
votes
1answer
51 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 ...
2
votes
1answer
26 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 ...
1
vote
1answer
41 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
vote
1answer
38 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
votes
1answer
50 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 ...
0
votes
2answers
400 views

Google's Deep Dreamer

I was just wondering on a more technical side, if anyone could explain what Google does to create these amazing images from it's deep dream system. Could anyone explain to me in a step by step way, ...
2
votes
2answers
339 views

find the actual size of an object from pixel coordinates

I am quite new to vision and OpenCV, so forgive me if this is a stupid question but I have got really confused. My aim is to detect an object in an image and estimate its actual size. Assume for now ...
1
vote
1answer
36 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. ...
1
vote
1answer
191 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++ ...
-1
votes
1answer
84 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 ...
5
votes
0answers
84 views

How to calculate Huffman code length without generating the actual huffman code?

Given a vector of elements, how can I calculate the length of the Huffman codewords without generating the Huffman code itself? Using Matlab, I was able to compute the Huffman code and and get the ...
2
votes
1answer
120 views

Compare phase and magnitude spectrum results of 2 Images

I have read that from Fourier transform we obtain magnitude and phase spectrum. The magnitude spectrum tells you how strong are the harmonics in a image and the phase spectrum tells where this ...
2
votes
1answer
509 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 ...
1
vote
0answers
63 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
votes
1answer
91 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
votes
0answers
49 views

Is there a way to tell a picture has been resized?

I need to evaluate if the picture was resized (upscaled). Are there any approaches to that already? If not, what do you recommend me to start with?
0
votes
1answer
35 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 ...