# Questions tagged [histogram]

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39 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 ...
9 views

### Measure that Compares an Actual Old Document from a Synthetic Old Document

I have collected dirty background images, below is the sample: I have also a collection of an actual image of a dirty document with text on it, just like below: My problem with my actual image of a ...
35 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 ...
20 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: ...
31 views

### How to apply logarithm-power histogram modification?

I'm trying to implement logarithm-power histogram modification using this formula: and here is my try: ...
140 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 ...
33 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 ...
21 views

### Hisotgram equalisation error, help with my code

Iam working on implenting a histogram equalisation of an image without using inbuilt functions specifcally imhist and histeq, I have, for the most part understood what do during a histogram ...
81 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 ...
70 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 ...
93 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 ...
44 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 ...
99 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 ...
142 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. ...
64 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 ...
276 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 ...
112 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. ...
644 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 ...
852 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 ...
57 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 ...
347 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 ...
2k views

### Measuring sharpness/contrast for autofocus

For the implementation of an auto-focus for the raspberry cam I need some measure of image sharpness. I used the following sample picture: The first approach was to compute the shannon entropy of the ...
93 views

### 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 ...
186 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 ...
491 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 ...
79 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 ...
154 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 ...
545 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 ...
5k 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 ...
105 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 ...
91 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 ...
488 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?
438 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 ...
116 views

### Gonzalez question solution

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 $\sigma$ ...
3k 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 ...
133 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 ...
12k views

### Histogram matching of two images using cdf

I have already calculated the cdf values of each image now i have to map the reference image values to target . I cannot use histogram equalization or interpolation I simply have to map them . ...
2k views

### Histogram and binary image in opencv? [closed]

I would like to compute how many zeros and ones (e.i. 255) in a binary image. The following code to generate a binary image by using Matlab. ...
434 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 ...
936 views

### What steps come after finding the gradients of the SIFT key points?

I am using a SIFT algorithm to extract features from an image. I understand that the SIFT descriptor first finds the extrema and then finds the gradient and direction of each of these interest points....
556 views

### Distance-metric for SIFT descriptors matching

Will using Cosine-Similarity or Histogram Intersection as distance-metric, for matching SIFT descriptors, help to get better results? Anybody tried on that ever?
473 views

### How to create a band limited signal of sine waves that is nearly uniform distributed

I would like to create a signal that is nearly uniform distributed (as depicted in Figure 1). It must consist of some single sine waves (e. g. 400 Hz, 430 Hz, 500 Hz) or a random band limited signal (...
154 views

### Encoding the HOG features

I have got a video containing 200 frames and i am extracting low level features at pixel level. Then i am dividing the entire frame in to small spatial patches (say of size 7x7) and creating a feature ...
7k views

### Why is histogram equalization called as “equalization”?

When output histogram is not same as reference histogram, why is the method called histogram equalization? For example below are two figures from http://en.wikipedia.org/wiki/Histogram_equalization. ...
771 views

### Image Contrast Enhancement based Sub-histogram Equalization Technique without Over-equalization Noise

I'm a computer science student and I have an assignment requiring me to implement the algorithm proposed by this paper but I'm hitting a roadblock trying to understand the implementation of one of the ...
1k views

### Calculating an HSV histogram

I have to compute an HSV histogram of a colored image. Is it same as an H-S histogram? I have found H-S histogram computation code everywhere. What is the method to change an H-S histogram to an ...
554 views

### Histogram evaluation for image quality concerning illumination

I'm currently trying to develop an algorithm to control the camera characteristic of a camera (the camera characteristic can be controlled to adopt it to the different lightning situation which can ...
160 views

### Histogram operation for improving visual object tracking

I'm developping a people tracking with nearest neighbour data association technique and kalman filter for smoothing/predicting. The tracker works quite good but sometimes it mismatch objects if they ...