# Tagged Questions

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27 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 ...
59 views

### Threshold value for a sparse signal

I want to calculate the threshold value for a sparse signal. So what is the method to calculate the threshold value? I have random signal with $N=1024$ and $K=20$. I down-sample my signal after that ...
38 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 ...
33 views

### Quantization threshold selection

I have the 256-bin histogram representing a distribution of the values taken by a certain descriptor element. This descriptor element takes the values in 0-255 range, hence 256 bins. I want to ...
35 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 ...
324 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: ...
159 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 ...
52 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 ...
47 views

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: ...
121 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 ? ...
90 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 ...
48 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 ...
76 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 ...
254 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....
892 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 ...
273 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 ...
235 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 ...
119 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 ...
463 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 $\mathbf{y}( = \mathbf{A}\mathbf{x}), \mathbf{A}$, ...
49 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 ...
723 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 ...
38 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 ...
580 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 ...
106 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 ...
341 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 ...
382 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 ...
202 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 ...
628 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 ...
389 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 ...
20k 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 ...
3k 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 ...
604 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) ...
4k 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 ...