# Questions tagged [histogram]

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32 views

### How to make frequency histogram from raw measurements?

I have a quadcopter with some motors. I'd like to run the motors at different speeds and analyze the different frequencies of the chassis vibration. A gyroscope+accelerometer in the center, measures ...
17 views

### Why is Histogram of Oriented Gradients only 0 to 180 degrees and not 0 to 360 degrees?

Why is Histogram of Oriented Gradients only 0 to 180 degrees and not 0 to 360 degrees? I can see in many videos that it's very common that atan which results values ...
• 417
1 vote
151 views

### main idea of Adaptive histogram equalization (AHE)

I want to understand the main idea behind AHE and the way for applying it manually with my hands. Wikipedia says: In its simplest form, each pixel is transformed based on the histogram of a square ...
239 views

### Mathematically show the problem of Histogram Equalization

Wikipedia - Adaptive Histogram Equalization says about classic Histogram Equalization: This works well when the distribution of pixel values is similar throughout the image. However, when the image ...
285 views

### purpose of histogram equalization

What is the main purpose of histogram equalization on image? Is it used to enhance contrast of image or is its goal finding a transformation which gets a more uniformly histogram? Although Wikipedia ...
1 vote
59 views

### Help on choosing compatibility test for classification algoritm

I have designed an algorithm for classification and I need to add a suitability or compatibility test for accepting a signal as an input. Basically, not all signals are suitable for processing by my ...
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444 views

### How to binarize an image using the triangle method?

I'm a college student taking an image processing class. My homework is to apply the "triangle method" on a grayscale image and binarize the image using the result. The problem is that I ...
1 vote
94 views

### How fast is an histogram suppose to decay?

I am working on a software which receives streaming audio data, is expected to process that data on the fly, and then outputs the results. The module I'm working on is expected to adjust the audio ...
• 111
215 views

### Inverse of filtering and inverse of equalization

Is comb filtering a reversible operation? If applied to a signal, can I restore the original signal from the filtered image? What about the histogram equalization operation? Is it reversible?
• 349
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### How to find the minimum no of bits required to express the filter coefficients in fixed point format from Histogram plot?

I have designed a filter in MATLAB and now I have to convert the filter coefficient in fixed point format from floating point format. For that my professor asked me to find histogram first and then ...
1 vote
1k views

### How can I create a histogram showing the RMS amplitude for each frequency bin of an audio file

Using Python or Matlab, how can I create a histogram in which each bin is equal to a proportional frequency range (e.g. one octave) and the data added to each bin is a count of the number of samples ...
335 views

### What is the x and y axis showing for this matplotlib.pyplot histogram of a .wav file?

The python code below generates a histogram from a .wav file, but what exactly does the histogram show? Is the x axis amplitude binned by sampling rate? Is the y axis a count of how many samples are ...
141 views

### Multivariate Histogram / CDF Matching for Image Color Matching

Suppose X is random variable that is spatial position in finite range, which its Cumulative Distribution Function (CDF) could be calculated easily, then if I have two random variable X and Y spatial ...
1 vote
291 views

### The Math of Histogram Matching

Please help solve the problem in the picture. I am confused due to the piecewise nature of the density functions. If it was a simple curved PDF, I would simply integrate over full range and use the ...
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27 views

### Which are the rules of choosing a target image for histogram matching?

With histogram matching we can transform an image's intensity distribution. But this idea is very subjective. Sometimes for choosing a target image we have options no better than a guess. But is their ...
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208 views

### 'Combed' Histograms

I have two FLIR Blackfly cameras that are identical outside of one being color and the other being mono. I set the ADC of both to 10 bit, and save the images in 16 bit. This results in the combed ...
1 vote
166 views

### Making images taken under daylight conditions appear as if they were taken at night using image processing elementary techniques

I know that these days' style-transfer GANs should be able to style-transfer day images into night images. I however prefer to do it using a set of elementary image processing manipulations, so I can ...
125 views

### Lightweight test for bimodal distributions?

Here, and in the stats stackexchange, seem to be answers that reference tests for bimodal distributions that involve iterative binning or iterative curve fitting methods. However "eyeballing" a plot ...
• 35.7k
132 views

### How to plot histogram of difference of two images using MATLAB

i would like to calculate difference of two images. Then, histogram of difference of two images. So I can plot a histogram but I am not sure whether it is true or not? Also, I am not sure about what ...
1 vote
181 views

### I can't implement plateau limit histogram equalization algorithm using MATLAB

i tried to implement this research paper using MATLAB. Unfortunately, my result is not same with the original result. Here is my try step by step: ...
1k views

### What Information Is Lost by Histogram Equalization?

I cannot think of a way to restore an original image after histogram equalization. But this latter seems to "enhance" (= increase contrast of) the image's details. What information is then lost by ...
1 vote
64 views

I plant trees in the north of BC for a living and have next to none sp experience, please be gentle :^] TLDR: The problem is essentially this: tracking and calculating the "height" of three ...
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200 views

### What Is a Weighted Local Histogram?

I'm reading through a couple of academic papers, and this terms often comes up "local weighted histogram". An example of quote is the following: First, cumulative histograms are built for every ...
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158 views

### Harmonics in Quantal Histogram

I'm studying what I believe to be a system that produces a (noisy) quantal response (i.e. there should be a minimum increment of response). To do this, I've plotted a histogram of some ~6000 amplitude ...
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207 views

### Image Histogram - What Is the Interpretation of PDF

For digital images (assume 2D gray scale image), the normalised intensity histogram is often treated as the probability distribution function of the intensity ie., intensity is treated as a random ...
• 43
1 vote
313 views

### From Uniform to 2D gaussian

I have a 2D uniform distribution. I would like to assign probability-weights in the distribution, according to the standard deviation to convert the distribution into a 2D gaussian. I know how to do ...
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203 views

### Image Contrast Enhancement Threshold Selection

I have a a set of 24bit images with bright reflective spots washing out the underlying detail. While I'm interested in tone mapping algorithms, since these bright spots are purely noise I would like ...
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282 views

### Histogram Counts of a 2d Matrix

I am currently working on a project in which I have a 10 x 2 matrix: A. I want to find the top 3 number of occurrences of each row using MATLAB. ...
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1 vote
174 views

I have a question regarding histogram equalization and adaptive histogram equalization. In which circumstance would it be preferable to use adaptive histogram equalization over histogram equalization ...
1 vote
472 views

### Entropy of enhanced image more than the original image

It is said that the entropy of an image is the information that it contains. Let us assume, that the entropy of an image f(x,y) is ...
• 265
133 views

### Histogram estimation (from sub-set of image pixels)

Problem: How to find gray-scale image histogram without iterating all pixels and binning them. Description: Suppose that I have large set of images with no common scene and of different resolutions. ...
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1k views

### Histogram Equalization Ignoring zero in Python

I wrote a small python code for histogram equalization (ignoring zero values) for an image but it is taking too long to run. Code is written with reference to wikipedia article on histogram ...
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1k views

### Python: How to calculate image perimeter orientation histogram?

I would like to find the perimeter orientation histogram of an object inside an image. The object is returned into an array but I don`t know how to find the orientation of its perimeter. I think the ...
• 103
1 vote
77 views

### Watermark insertion process in image

I'm new in the field of image processing and I'am trying to implement a watermarking algorithm (for medical images in DICOM format) based on this paper. As written in the paper, this algorithm is ...
• 229
1 vote
456 views

### How to Generate a vector map for histogram equalization

Assuming I have a gray scale image Im with $0:255$ levels of gray, I want to generate a vector map that will preform a histogram equalization on the image. I have ...
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### Histogram Equalization

I am reading the etext on Digital Image Processing by Gonzalez and under the section on Histogram Equalization, an equation which is apparently basic is shown. I have no clue what the equation means ...
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280 views

### MATLAB: get members of histogram populations EXCLUDING those inbetween

The Problem I have a (noisy) square wave signal and need to extract the data points that make up the 'baseline' and 'plateau' ONLY. I do not want data from the rise and fall. So far I have ...
• 41
1k views

### How to detect whether a signal is unimodal or bimodal?

I have to kinds of signals. The first type of signals are such that their histograms are unimodal (one-peaked). The second type of signals are such that their histograms are bimodal (two-peaked). How ...
• 41
1 vote
88 views

### How to gather similar objects in an image?

I am working in a traffic tracking app, I am using a background subtraction approach to obtain information about the moving vehicles. After some morphological operations I obtain blobs of the moving ...
369 views

### Equalization and then Sharpening vs Sharpening and then Equalization

This was a question from an exam of digital image processing: "Working with low contrast images, an elective method to enhance details and improve contrast is to apply in cascade an equalization of ...
1 vote
771 views

### CLAHE - Redistributing excess pixels among histogram bins

In order to clip an image's histogram to a maximum value, according to the CLAHE algorithm, the excess pixels (above the clip limit) will be distributed equally among all the histogram bins (While ...
• 121
1 vote
6k views

### Histogram matching (specification) in Python

I'm trying to implement an algorithm in which I first pad each row of the image with a fixed amount of new pixels in a certain range, apply Gaussian smoothing to the row cumulative histograms in ...
297 views

### How do i detect if an image has a gradient or not?

I have coloured images, some may be just clipart, some may be artwork, both could be with or without gradients. Before i run a colour counting algorithm on them, i want to detect if the image has ...
114 views

### Noise in Digital image

in Digital Image Processing restoration ,from my understanding after reading articles , it's seems that the noise must be dominant in the histogram of the image , which is make it possible , to get ...
• 113
579 views

### Does anyone know how to overlay a equalized CDF plot with equalized histogram in matlab?

I am willing to overlay a equalized cdf with equalized histogram in matlab. But it's really hard to find any recommends. so if you can, would you please let me know about that?
• 101
555 views

### Getting 16 bit image statistics in Photoshop

The histogram in Photoshop for a 16-bit image downsamples to 8 bits, showing a tonal range of 0 to 255. I appreciate to show tonal ranges for a 16 bit image a horizontal zoom function would be ...
• 101
1 vote
138 views

### Convert Gaussian Like Histogram into Uniform Analytically

If I have the histogram of an input image as Gaussian probability density function of the form: $$P_r(r)=\dfrac{1}{\sqrt{2\pi}\sigma}e^{-\dfrac{(r-\mu)^2}{2\sigma^2}}$$ where: $\mu$ and $\sigma$ ...
• 11
4k views

### Histogram Intersection with two different bin sizes?

I have two images: A and B. Image A is a screenshot of image B, the original image. While there is noise in image A, the original features are still distinguishable. Histogram intersection tells us ...
• 141
1 vote
391 views

### float image to integer type image

I have a multispectral satellite image and I would like to "transform" each of the image bands into one with integer values. For example to stretch? the image between 0 and 255. Not sure how to ...
• 121
1 vote