# Tagged Questions

A form of signal processing where the input is an image. Usually treating the digital image as a two-dimensional signal (or multidimensional). This processing may include image restoration and enhancement (in particular, pattern recognition and projection).

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0answers
40 views

### Image classifier in python for few samples

I have 150 pictures that represent archeological signs and 5 categories to which they belong. These pictures have features like circularity, roughness and elongation that are expressed as continuous ...
0answers
12 views

### Which features to extract for classifying segmented zones of an image into two classes “handwritten text” and “graphics”

I have some chemical document images segmented into different zones, some zones represents "handwritten text" and others represent "graphics". I want to classify this zones into two classes, one for ...
2answers
73 views

### Application of Poisson distribution to image processing

I'm trying to write a program to detect water bubbles in heated oil. I've applied a canny edge detection filter to the image and the results look like the following: No bubbles: ...
0answers
23 views

### How can you reconstruct “base” (profile/headshot) image of face using several obscured images of the face?

I recently read a paper titled "3D Face Reconstruction from a Single Image using a Single Reference Face Shape" which got me thinking about the fact that it is rare for one to encounter unobscured ...
1answer
300 views

### How to calculate the signal-to-noise ratio (SNR) in an image?

I am working with an image X, I apply the "adaptive median filter" in it and I get the image Y. I'd like to measure the SNR in both in order to evaluate the quantity of noise deleted. I know the ...
0answers
23 views

### Classifying foreground vs background for ellipse shapes

I have images of ellipse shapes which are read in as a matrix of pixel intensities. I'd like a way to be able to classify whether a pixel is foreground (belonging to ellipse) or background (not ...
0answers
42 views

### Image similarity database

I'll preface this by stating I'm very new to computer vision. I took a Stanford Machine Learning course on Coursera, and that is the extent of my experience. I'm working on a free-time project to ...
0answers
42 views

### Markov random field and iterated condition mode

I have spent a lot of time studying MRF (applied to images) but still can't grasp the idea. Could you please clarify these ideas: What is the clique potential? What is a clique in image, and do they ...
2answers
229 views

### does it make sense for non-negative data to subtract the mean and divide by the std dev?

It is a very usual procedure to subtract the mean and divide by the standard deviation in a set of data. If we deal with non-negative data, i.e. image, (in [0,1] or [0,255]), does this procedure make ...
2answers
133 views

### Auto crop black borders from a scanned image by making stats about gray values

I'm writing a computer program to automatically detect black noisy borders on scanned images and crop them off. My algorithm is based on 2 variables: gray mean value (of the pixels in a rows/columns) ...
2answers
193 views

### Classification on principal components

For my research I am doing classification on the dataset of three variables. I run unsupervised clustering (based on a histogram peak technique of cluster analysis)and the result I evaluated visually ...
1answer
85 views

### bag of words in an online configuration, for classification / clustering

I have a set of image documents. I extract text keywords from this images using OCR to represent each image as a bag of words (a vector where each value is the number of occurrence of a word in the ...
1answer
81 views

### Suitable data preprocessing for an image recognition task: normalization ,standardization or neither?

I aim to train my classifier for an image recognition task. What kind of preprocessing steps I need to take to enhance my results? (I have >40000 images with >700 pixels so large amounts of data with ...
2answers
273 views

### Image Clustering with K-means - Postprocessing

I did some clustering on an image (each pixel is an observation that has 5 variables associated with it), I get pretty detailed results but they are a little bit noisey... I think. I used K-means. ...
0answers
15 views

### how Neural Network works on image recognition [duplicate]

Possible Duplicate: How does neural network recognise images? I am trying to learn how Neural Network works on image recognition. I have seen some examples and become even more confused. In ...
3answers
803 views

### How does neural network recognise images?

I am trying to learn how Neural Network works on image recognition. I have seen some examples and become even more confused. In the example of letter recognition of a 20x20 image, the values of each ...
0answers
98 views

### Algorithms and libraries to do fast character recognition

I just found out about Pleco the other day and was wondering how they achieve this type of accuracy: http://www.youtube.com/watch?v=x7VTo0656Rc I have a strong background in machine learning, yet ...
1answer
73 views

### Document image analysis and retrieval with online incremental clustering

Is there any interesting problem in the area of "Document Image Analysis and Retrieval" which by nature needs an online/incremental clustering process ? The problem may be in the context of "Logical ...
2answers
132 views

### The most common extracted features for image recognition

I want to build a neural network, but because I have high resolution pictures, I rejected the idea of passing the entire image to the NN. I was wondering what are the most common extracted features ...
1answer
168 views

### How to measure the number of people in a picture of a crowd?

Background: Israel (and the middle east in general) is filled with protests. I am curious, when given a picture, to estimate how many people are in that picture (often a picture of a large crowd). ...
0answers
196 views

### How to combine features extracted by PCA, LDA and LBP?

What I'm thinking is to combine PCA features, LDA features and LBP features together to get a higher accuracy, since I think the three features are all kind of histogram vectors and when we decide the ...
1answer
134 views

### Comparing two sets of pixels to determine whether they belong to the same object

I have two sets of data, and I want to know if the second set is sufficiently different from the first to be considered different. More specifically, I have a sample set A from a number of pixels in ...
1answer
173 views

### Help on SVM for road image processing

I am new to SVM. I would like to use SVM to segment/cluster/classify a road image into two distinct regions i.e. drivable region and non-drivable region. Unfortunately, I do not have any images where ...
1answer
115 views

### I have a statistic, how do I calculate its distribution?

I am comparing images for correlation. The images are all correlated, but I would like to determine when one pair is much more highly correlated, relative to another pair. I am using as a statistic ...
1answer
497 views

### Using PCA for detecting similar regions in an image

I'm trying to understand an algorithm that detects similar regions of an image using PCA. The algorithm essentially divides the image into overlapping square blocks and then does PCA with each block ...
1answer
243 views

### How to run K-means clustering on data points of varying dimensionality?

I'm trying to aggregate $T$ local image descriptors (i.e. histograms) into a vector, namely, the Fisher Vector as described in this paper by H. Jégou et al., Aggregating local image descriptors into ...
1answer
161 views

### Definition of “Natural Images” in the context of machine learning

Whilst reading up on the Deep learning literature, I noticed that a few variations on the standard network structure that were created specifically to better model "Natural/Real Images". For example, ...
1answer
118 views

### How to select discrete cosine transform coefficients as a feature vector?

I need to use DCT on frames of videos as a feature vector to train a Feed-forward artificial neural network, but the problem is the large number of coefficients (in thousands or so). How can I choose ...
1answer
303 views

### Creating tree splits in Hough forest

I am working on my thesis and working machine learning. The overall problem is Detecting and Recognition of Road Inventory. For my research part I am looking into decision trees, especially Hough ...
3answers
659 views

### What is the most accurate way of determining an object's color?

I have written a computer program that can detect coins in a static image (.jpeg, .png, etc.) using some standard techniques for computer vision (Gaussian Blur, thresholding, Hough-Transform etc.). ...
2answers
94 views

### Averaging images

I want to see if it is possible to analyse openly available images (from google, flickr, etc.), and conclude something from them (the same way one might do this from census data but with images as ...
2answers
100 views

### How is EM used in the sense of data mining on images?

I understand how EM is used in the sense of estimating the Gaussian model that underlies a set of data, but its unclear how this is applicable. I am trying to understand how EM might be used to ...
1answer
296 views

### What is the level of measurement of image data?

Question: This is a bit of an abstract question, but bear with me. I am averaging images, to try and deduce what the average image of a specific subject looks like (just out of curiosity, it might ...
1answer
49 views

### Where do I find large face datasets?

Are there any large, freely available (but not necessarily labeled) face datasets out there? The ones I have seen usually range in the hundreds, but for unsupervised feature learning it would be ...
0answers
215 views

### Similarities between different size matrices, rescaling problem

Given a series of matrices {$M_i$($m_i\times n_i$),i=1...k,$m_j,n_j \in$random} if we rescale (resize) all matrices into a ...
1answer
296 views

### How to equalize histograms

I am learning some image processing stuff and equalizing a histogram comes up as an important topic. I have followed the procedure listed on Wikipedia but the resulting equalized histogram does not ...
2answers
154 views

### Do image recognition efforts always rely on machine learning and statistics?

This is something I've always wondered. Consider the Kinect. It takes its 3d image data and manages to recognize that a human is contained at a given boundary. Are these types of technologies ...
1answer
724 views

### 2D object recognition using MATLAB

Have you any idea about implementing 2D object recognition with MATLAB? Which characteristics of objects can feed a neural network? It's my training data-set (provided by ETH University of ...
0answers
495 views

### Template matching involving scale-, rotation- and shape-invariant transformation

I am not sure whether this is the right place to ask this question, but any possible answer will help. I want to apply some form of template matching on these set of pictures. This is the template ...
2answers
359 views

### Valid method to analyze spatial correlations in images?

Is there a reasonable way to quantify the amount of local correlations in an image? For example, I want to justify the correlations between a neighbourhood of pixels is much higher than the ...
1answer
281 views

### Cross variogram with a moving window

I need to generate cross variograms of images using moving windows. For that I use the following equation:  ...
1answer
429 views

### Detect circular patterns in point cloud data

For some volume reconstruction algorithm I'm working on, I need to detect an arbitrary number of circular patterns in 3d point data (coming from a LIDAR device). The patterns can be arbitrarily ...
1answer
162 views

### Hidden states in hidden conditional random fields

I am trying to study hidden conditional random fields but I still have some fundamental questions about those methods. I would be immensely grateful if someone could provide some clarification over ...
0answers
88 views

### How to call intensity domain elements? [closed]

When working with image histograms, I often find my thought stumbling against the lack of exact word to name "intensity element". When someone needs the analogous term for time domain element, he uses ...
3answers
4k views

### How to assess the similarity of two histograms?

Given two histograms, how do we assess whether they are similar or not? Is it sufficient to simply look at the two histograms? The simple one to one mapping has the problem that if a histogram is ...
8answers
13k views

### Detecting a given face in a database of facial images

I'm working on a little project involving the faces of twitter users via their profile pictures. A problem I've encountered is that after I filter out all but the images that are clear portrait ...
1answer
473 views

### Matlab image blending

Hey guys. I got two images from video frames. They have a certain portion of overlap. After warping one of them, I'm currently trying to blend them together. In other words, I would like to stitch ...
3answers
297 views

### How to find text blocks in a scanned document?

I am trying to detect text in a scanned document by examining variations in the lightness of the scan collapsed vertically. Here's a sample of the input I would receive, with the lightness plot of ...
4answers
400 views

### Suggested R packages for frontier estimation or segmentation of hyperspectral images

An hyperspectral image is a multidimensional image with more than 200 spectral bands i.e. an image for which each pixel is a vector of dimension 200 (most often it is a sampled spectral curve that is ...
2answers
2k views

### Differences between Baum Welch and Viterbi Training

I am currently using Viterbi training for an image segementation probelm. I wanted to know what are the advantages/disadvantages of using the Baum-Welch algorithm instead of Viterbi training.
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