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2
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2answers
95 views

Detect valleys of a signal

I have raw values that are coming directly from a sensor (on the fly). These values are coming from a wearable sensor installed on a cows neck. When the cow ruminates (meaning that it chews food that ...
0
votes
0answers
18 views

Extracting overlapping features in an image when individual features are known

Consider this image: Which is a sum of two different sets of features: The first is a collection of overlapping squares with value of 5 and the second is a collection of overlapping squares with ...
1
vote
0answers
31 views

Binarization, and then thinning/skeletonization

I have pictures of networks, like the one below, and my goal is to obtain the network's skeleton from processing those images. My approach lies in two steps, first I convert grayscale image to binary ...
1
vote
2answers
38 views

Double Threshold Mechanism

I was studying an article about optical music recognition. Somewhere in segmentation section is mentioned that The final step consists of isolating the note heads. This is performed by using a ...
0
votes
0answers
10 views

Segmenting objects using colour thresholding

I'm using intensity-based thresholding as the first step in a method to segment typically white objects from a dark grey background. It works well, but some image have another particle that is dark ...
3
votes
0answers
56 views

Energy Detection in Presence of Colored Gaussian Noise

Before asking my question, let me introduce the context: For spectrum sensing based on energy detection, which has been widely studied in presence of AWGN, the optimal detection threshold is computed ...
0
votes
0answers
18 views

What is the best way to select pixels with a specific color?

I want to select all yellow pixels from an image. The first idea that comes into one's mind is to consider a reference RGB value as yellow, and to calculate the L2 norm between every pixel and this ...
0
votes
1answer
38 views

Why is it called 'multi-level thresholding', if only the best threshold is selected?

I'm referring to Otsu's thresholding, and saw this from his paper: When he says he's trying to maximize the between class variance of thresholds k* 1 and 2, is it the threshold with maximum value ...
0
votes
1answer
177 views

In plain English, what exactly are the within and between class variances in Otsu's thresholding?

For the past week I've been through numerous research papers and tutorials on Otsu's thresholding. Even wrote to the authors, but every single one of the explanations are in terms of "Class" and "...
2
votes
1answer
49 views

Is document image binarization a closed research field [closed]

A lot of work has been done in the field of document image binarization. Is it a closed research field or still an interesting challenge area? I am new in the field, and just curious.
0
votes
1answer
121 views

select local maxima in energy signal

I have the following plot which represents the RMS energy of a signal over time. The energy goes up and down with varying maximum amplitude. I want to keep the portions of the signal where the energy ...
0
votes
2answers
257 views

Optimal Level of wavelet decomposition for denoising

If a certain mother wavelet is defined and the optimal threshold shall be defined via Donoho, how can I define the optimal decomposition level to achieve the best denoising results.
1
vote
1answer
115 views

Motion detection one threshold over dataset

We're working on a project where we have to detect the moments where motions happen in a medical scene. I have a data set of 20 videos that are closely resemble (Same camera & configuration used, ...
1
vote
0answers
91 views

Fast greyscale image segmentation on 16x16 image

I have a 8-bit greyscale 16x16 image where I want to extract coherent shapes with a more or less consistent pixel arrangement if possible (like: a rectangle, staircase, line). Currently, I'm doing ...
1
vote
0answers
71 views

How to classify images based on the amount of colors in the image?

I have a problem where all images have the same object; however, these objects can either have number_of_colors<=3 OR number_of_colors>3 and images are not labeled. My attempt starts by ...
0
votes
0answers
40 views

Is this a valid thresholding approach?

I am using a wavelet transform and am testing the following approach to thresholding: All coeffients (whatever their value) after the first N are set to 0 So if my timeseries window is 128 ...
1
vote
4answers
1k views

implementation of Fourier denoising with hard threshold

I just tried the Fourier denoising method with a hard threshold and my code is as follow: ...
0
votes
2answers
263 views

Diagonal vs non diagonal processing for audio denoising

I am going through a technique for audio denoising by block thresholding. Here is the paper: http://www.di.ens.fr/~mallat/papiers/AudioBlock.pdf According to the definition in the paper for ...
1
vote
1answer
94 views

Locally Adaptive Thresholding - How to Detect if Image Block is Uniform

I need to implement a locally adaptive threshold algorithm on a grayscale image in matlab. I use a sliding window over the image and calculate the threshold for the block using Otsu's method, which ...
3
votes
0answers
61 views

Clarification about wavelet thresholds

I am trying to wrap my head around the original wavelet shrinkage papers of Donoho and others from the mid-90s. There are a couple of curious things that confuse me, and I'd appreciate some input: ...
0
votes
1answer
270 views

How to choose suitable segmentation process for image processing

Hello I'm new on image processing. I know there are a lot of threshold and region growing algorithms to use. But I would like to know what is the trick for choosing suitable method for an image ? ...
1
vote
1answer
120 views

Re sizing and thresholding small font scanned Arabic words

I am working on an arabic OCR for printed scanned documents ... Some of the scanned documents may written with font size of height 8 which is quite small ... I want to resize the height to 60 pixels ...
0
votes
1answer
95 views

Binary classification of grayscale image with little texture

I want to carry out a binary classification/segmentation on a grayscale image with very little texture. The only prior knowledge that's supposed to be available is that the object of interest is ...
1
vote
1answer
103 views

Thresholding a difference image with a very high kurtosis

I have an difference image produced by substracting two images of a certain location taken a two different time steps. The resulting image of this operation shows a histogram with a very large peak ...
0
votes
1answer
748 views

What are the various techniques for detecting Walls in the Building(Architectural) floor plan Images?

I have to process building floor plan images to extract Walls from the structure. It is trivial in case of binary images; but the images in our case are colored, and each have different color of walls....
0
votes
1answer
2k views

Otsu Thresholding : Why 'minimum within class variance' gives the optimum threshold?

I was trying to understand the Otsu thresholding algorithm in image processing. For that purpose I found a useful link. I got the algorithm flow, but a fundamental doubt arises. Why 'minimum within ...
1
vote
0answers
391 views

GLOBAL THRESHOLDING using histogram

There is a recursive way of finding threshold in the image using histogram that are biomodal, and is as follows: An automated procedure for bimodal histograms : Select an initial estimate of T ...
2
votes
0answers
401 views

Shifting of Shift-Invariant Wavelet Transforms

Main Question: Why would iterative wavelet/inverse-wavelet transforms cause a shift along the x-axis for undecimated (shift-invariant) wavelet transforms? I am attempting to remove backgrounds from ...
1
vote
2answers
168 views

make a threshold frequency based on percentage of frequencies less than that?

Using MATLAB signal processing toolbox, I have created signals like dirichlet, chirp and etc and and obtained their fourier and cosine fourier transform. Now I want to find the frequency where for ...
4
votes
2answers
976 views

Iterative Hard Thresholding python implementation [closed]

I'm trying to implement the Iterative Hard Thresholding recovery algorithm for compressive sensing in python. It is a very simple algorithm, given $ \mathbf{y}( = \mathbf{A}\mathbf{x}), \mathbf{A}$, ...
1
vote
0answers
53 views

Thresholding for Movement Classification

I have an application which creates a Gaussian model of the background based on consecutive frame difference and auto-generates a threshold for separating no-changes to movements. The application ...
3
votes
1answer
1k views

Onset Detection Peak Picking

I have a guitar music signal and I want to detect the onset points via energy. This is the signal example: This is the energy plot: My question is what would be the best method defining the ...
0
votes
1answer
42 views

Scaling down the modal value when thresholding

I have a piece of code that I am translating and I am trying to understand the reasoning behind it. The application here is thresholding medical (cellular) images. The function in question takes a ...
6
votes
1answer
790 views

Deblurring algorithm to precede thresholding - speed over accuracy

I'm writing an app that recognizes Sudoku puzzles from a camera input. I'd like to remove camera blur from the images to improve recognition. Here is an example image: Since I'm processing a ...
0
votes
1answer
119 views

Image thresholding while retaining “underneath” contents

I have sample images, and I need to extract certain features that depend on color. Images are more like line art, contours, and consist of various line forms, and several colors. I can extract ...
5
votes
1answer
442 views

Adaptive thresholding based on number of pixels

I'm thresholding an image where the threshold value is a count of the pixels such that for instance if the threshold value is 100, any color value which has less than a 100 pixels is classified black ...
7
votes
1answer
468 views

White Road Sign Detection [duplicate]

Possible Duplicate: How to extract traffic signs from a photograph? I am working on a project which involves detecting north american speed signs (black/white) using a 720p HD camera. My problem ...
2
votes
1answer
229 views

Will binarization / thresholding of image yield better results when performed in a linear color space?

All thresholding algorithms I have read about make no mention about color space, except sometimes using pixel values between 0 and 255 as an example. But since the intensity output by a monitor of a ...
9
votes
3answers
1k views

Segmenting pills from the background

I just recently started out with Image processing and taken up a course related to it in Grad school. But I already have a project to do without too much information about the subject, however I've ...
6
votes
3answers
597 views

DCT and Hard Thresholding

If I have an Image and i find the DCT and then apply hard thresholding on the coefficients and then IDCT then I have attenuated the noise. Can someone please explain in detail or point me to the ...
32
votes
3answers
37k views

What are the most common algorithms for adaptive thresholding?

Adaptive thresholding has been discussed in a few questions earlier: Adaptive Thresholding for liver segmentation using Matlab What are the best algorithms for document image thresholding in this ...
6
votes
2answers
4k views

Otsu binarization with value preservation

I'm trying to implement a modified version of the otsu binarization algorithm. I'm trying to binarize document images. But in the binarization procedure I want the object (in this case the text) to ...
8
votes
3answers
958 views

Determining optimal binary decision rule threshold from observations with unknown priors?

Given only observations of a binary signal perturbed by Gaussian noise with unknown prior information, how can I estimate the optimal decision threshold? ( No, this is not a homework question) ...
5
votes
3answers
5k views

How do I compare two resultant images from different binarization algorithms?

I have a binarized image to which i add noise and then try to filter out the noise using various thresholding algorithms such as otsu and niblack.How can i compare the resultant image with the ...
9
votes
4answers
2k views

How to do De-Houghing of a Hough transform'ed Image?

I'm working with code found at Rosetta Code for creating a Hough transform. I now want to find all the lines in an image. To do so I need the ρ and θ values of each of the peaks in the Hough space. A ...
45
votes
6answers
16k views

Best way of segmenting veins in leaves?

I have done a lot of research and found out methods like adaptive thresholding , watershed etc that can be used of detecting veins in leaves . However thresholding isn't good as it introduces a lot of ...