# Questions tagged [image]

This tag covers signal processing where input is an image, such as a photograph or video frame and the output could be an improved or altered image, parameters related to the image or information about features within the image.

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24 views

### Image Z Coordinate Clarification

I'm trying to understand 3D image reconstruction, and want to clarify how we can find a z image coordinate. Is the z coordinate for image coordinates (x,y,z) the focal length since that's the distance ...
20 views

### What exactly is "connectivity" between pixels in an image?

So, my professor says that two pixels are connected if: they are neighbours; and their intensities satisfy a specified criterion of similarity. And depending on the type of neighbours they are, they ...
12 views

### Convert pictures from the same camera with different FOV to pictures with same FOV

I have a camera device that produce two pictures at the time: depth picture with FOV: 87° × 58° RGB picture with FOV: 90 × 65° I expect that they "share" the same objective so their origin ...
30 views

### Image conversion - raw ultrasound data to convex image

As a project, I'm trying to decipher raw data coming from a medical ultrasound device. The data contains a 128x1008 matrix. Each one of the 128 columns represents a sensor element. Each row in each ...
14 views

### how to identify the main segmentation step in a paper?

I am trying to summarize the segmentation methods submitted in the Cell Tracking Challenge. Currently, I'm having a problem in identifying the main segmentation step used in each paper. How to ...
38 views

### How to Remove Temporal and Fixed Pattern Noise and Apply Tone Mapping?

I have a video, whose frames I have extracted and require to work with. 16 bits and grayscale images. My task is to improve the quality of the images, by removing the noise + adding tone mapping and ...
15 views

### What are some good references that define images from a statistical point of view?

I know that images can be studied and understood as 2 dimensional signals. However, I hope you can point me towards references that define and present images rigorously in terms of realisations of a ...
86 views

### Is there a way to find the contours of instances in a binary mask image by color?

I need to find the contours for each of the instances of microscopic cells in a binary image mask of dimensions 256 x 256 shown below. My approach involves thresholding the image to get a binary mask ...
159 views

### Locate Non Homogenous Areas in an Image

I need to choose some points on an image. These points should be chosen more where there is lots of color changes, transitions and variations. Which techniques can I use for determining where most ...
65 views

### Basic Wiener application

I'm trying to filter this $g(x,y)$ WGN added image My Wiener filter is: $$H(u,v) = \frac{P_{f}}{P_{f}+P_{n}}$$ Where the image power spectral density $P_{x}$ is estimated as $\frac{|X(u,v|^{2}}{N^{2}}$...
77 views

### How to enhance thermogram image in grayscale?

I'm trying to do some image processing to improve the image below but I'm having some trouble. I already tried to do histogram equalization followed by laplace sharpening, I tried to implement a ...
27 views

### How would you process this image?

I got this image: I need to keep only the part in the center (I mean, the circle with texture inside). How would you do it in Python? I'm trying to use Hough Transform, but some times it detect wrong ...
31 views

### What is Label Refinement in the Context of Image Segmentation

I have been reading the paper entitled Measures of Similarity by Unnikrishnan and Herbet, in which they discuss some metrics to evaluate image segmentation. They use the word refinement of labels/...
52 views

### Removing feature matched outliers within same image using RANSAC

I'm a student working on a copy move forgery detection algorithm. I have a forged image. By far I have, Found keypoints and descriptors from the image Matched the descriptors using 3 Nearest ...
16 views

### How can i center the optical mark image?

I want to recognize optical mark using image processing algorithms. There is a wide variety of optical paper and i want to recognize all off them. For example; If i create a template I can superimpose ...
36 views

### Image downscaling methods

I am researching downscaling methods for image downscaling. I've both read and found area-averaging to work well in Python using CV2, but the settings in MATLAB allow for it's bicubic interpolation ...
57 views

### What exactly is a connected componnent in an image?

The following is a paragraph from "Digital image processing, 4th edition, Gonzalez and Woods". Let S represent a subset of pixels in an image. Two pixels p and q are said to be connected in ...
56 views

### Image convolution using FFT

I just can't get my head around Fourier transform and convolution in 2D. I am trying to implement image convolution using fast Fourier transform (in julia). So the first thing I need to do is to pad ...
33 views

### T1 Mapping in Python?

I'm trying to write a simple program to perform T1 mapping of a few MRI Images. My understanding is that all I need is to plot the pixel intensity values by inversion time then fit a curve. The output ...
77 views

### Beginner Educational Resources

New member here. Recently got hired into a mid level EE position. Have a BSEE but performed more radar performance analysis at a higher system level previously. In my new group we're doing a lot of ...
33 views

### How to calculate the magnitude while calculating Blur in an image using using OpenCv based on Fast Fourier Transformation

I am working on image blur detection and found 3 methods for it. One is Laplacian Method but it works good with Gaussian, average, median and other distribution ...
51 views

### How is non-integer upres downres (1080p game on a 1440p screen etc) calculated

Please redirect me if this is not the right place to ask. I was unable to find a straightforward answer to this question. What I am wondering is, if I am playing a 1080p game on a 1440p display, what ...
11 views

### Correlated signal components from uncorrelated and incoherent source after reflection

To this point, it has been assumed that the point sources composing the source are uncorrelated, generating fully incoherent signals. Thus, capturing the reflected signals and after sufficient time ...
77 views

### How to come true the convolution with a 2-D array in frequency domain with python

I use the pretty simple example used in many books to understand the convolution in the frequency domain. But I cannot find the real results. ...
15 views

### How to obtain height above ground, angle the pixel’s local surface normal makes with the inferred gravity direction from depth map of image?

For extraction of the HHA features from the image depth map we need to calculate the height above ground, angle the pixel’s local surface normal makes with the inferred gravity direction. How to ...
40 views

### SAR spotlight raw signal database

For practicing spotlight processing, i am looking for I/Q baseband signal from a SAR airborne or spaceborne system. In my research I have only found processed image from : eoweb geoportal https://...
789 views

### How to make a contour smooth in OpenCV

I am using OpenCV(4.5.1) and trying to extract a smooth contour of an object on my image. Firstly I got the contour by: ...
68 views

### How to find a pixel's image coordinates by its rgb value in MATLAB? [closed]

How would one find the pixels that match an RGB value in a matrix in MATLAB? Let's suppose that I want to find the image coordinates of pixels whose value is $RGB=(144,127,11)$ for a given image in a ...
152 views

### kernel to calculate second order partial derivative of digital image

im working on image stacks, and I need to calculate second order partial derivatiatives of it. I already know how to calculate derivative on x and y axis, using coefficients calculator: https://web....
29 views

### What is the between spatial frequency of an image and pixel size of the sensor?

In my lecture notes about the sampling of an image I've written that: Since pixels have a finite dimension the spatial frequency response is attenuated before the "ideal" Nyquist frequency ...
36 views

### Multivariate Histogram 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 ...
42 views

### Where 2-D DFT is necessary in image processing applications instead of 2-D DCT?

As we know the 2-D DCT is a real-valued kernel and less computational complexity and it used in several image processing applications like image compression etc. 2-D DFT is a complex kernel and high ...
453 views

### Is the Laplacian Filter an High Pass Filter (HPF)?

Is this kernel name as mean difference kernel or Laplacian filter? Is mean difference just a method?
22 views

### Feature extraction for IRIS recognition

What are types for feature extraction in iris recognition? How can I divide it on types which detect phase, edge, etc.?
28 views

### LPF and HPF filters in ENVI

Since we know about convolution filter in image processing, it is basically a matrix applied to an image and a mathematical operation comprised of integers and it works by determining the value of a ...
24 views

### feature extraction techniques for iris recognition

I want to ask how I can divide feature extraction techniques to feature detectors and feature descriptors. I have big problem how to understand it. For example I can use Gabor filters (feature ...
29 views

### Where do you recommend getting "standard" images for testing algorithms?

I've noticed that there are a LOT of websites which claim to have a standardized repository of images (for image processing algorithms). However, I don't know which ones are actually trusted by the ...
95 views

### Should Edge Detection Be Applied in Spatial or in Frequency Domain?

I want to ask why everywhere is used to do edge detection in spatial domain and not in frequency domain with FFT of image and apply HP filter. Thank you.
23 views

### How can I compute the result of the magnitude of edges of an image?

I have a random image with 11x11 pixels. In the center of the image is a square of 5x5 pixels. The gray level of the background is 0 and the gray level of the square is 50. How can I compute the ...