# Questions tagged [image-processing]

In general, image processing is any form of signal processing for which the input is an image, such as a photograph or video frame.

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### How Do Steerable Pyramids Work?

I'm reading a paper about texture synthesis using pyramids, and the very first section mention two methods for constructing pyramids, one is the Laplacian Pyramid (which I'm quite familiar with), the ...
3answers
655 views

### Image Pyramid Without Decimation

I have an image processing algorithm which uses Gaussian and Laplacian Pyramid Decomposition. At each level of the pyramid the algorithm decimates the previous level by a factor of 2. The LPF the ...
1answer
233 views

### Band Limit in Gaussian Pyramid

In the paper The Laplacian Pyramid as a Compact Image Code, it says The pyramid algorithm reduces the filter band limit by an octave from level to level. How is the conclusion drawn? Is this related ...
1answer
97 views

### Critically Sampled Laplacian Pyramid from 2nd Generation Wavelet

I'd like to know if a technique I have in mind is already used and has a name I can look up, and whether it is likely to work and be useful! My aim is to produce a discrete wavelet transform that is ...
2answers
328 views

### Can Aliasing Happen in Laplacian Pyramids?

I want to use the Laplacian pyramid framework for representing images. The The Laplacian Pyramid as a Compact Image Code's language seems to provide freedom in the choice of blurring/interpolation ...
1answer
88 views

### Energy Preserving Laplacian Pyramid

Both Discrete Wavelet Transform (DWT) and Undecimated DWT possess an important property of energy preservation: on each level $$\sum_i W_i^2 + \sum_j V_j^2 = \sum_k X_k^2$$ where $W$ and $V$ are ...
0answers
96 views

### Understanding Upsampling Filter in Laplacian Pyramid

For the construction of a laplacian pyramid, images are downscaled and then upscaled again. My question is what is a wise decision of the kernel mask for the upscaling task ? In more detail, lets say ...
1answer
419 views

### SSIM(YUV) vs. SSIM(Y): Values Are Very Different

I'm seeing some weird results when trying to compare image qualities in a few different color spaces. Have a look at my graph: I want to compare with another publication, which reported PSNR(YUV) and ...
1answer
331 views

### How to Validate Bilateral Filter Implementation?

For this may be a X-Y question, I'm providing the full background story: I'm trying to test for the correctness for a fixed point implementation of bilateral filter written in C. My current approach ...
1answer
2k views

### Improving Canny Edge Detection and Contours Image Segmentation

I am working on an image segmentation project to identify playing cards on varying backgrounds. For my use case I care most that I accurately extract all the cards in the image; false-positives are ...
1answer
939 views

### What's the Difference Between UQI and SSIM Measures for Image Similarity / Quality?

I'm studying image quality assessment (IQA) problem and I'm currently learning about quality measures UQI and SSIM, I know UQI is a predecessor of SSIM, but they look exactly the same for me...
1answer
114 views

### Which Noise Reduction Algorithms Are Used in Commercial RAW Image Processors?

I'm trying to guess what noise reduction algorithms are used in commercial processors for raw images from digital cameras. I find this fairly easy to do for the sharpening algorithms (most use unsharp ...
2answers
27 views

### Restore RGB Values from Luminance Value?

I am not sure, but can we get RGB (Red-Green-Blue) values from calculated luminance value for each pixel? ...
3answers
71 views

### Can the colors of an image be interpreted as “virtual” Doppler effect? [closed]

In astronomy, the Doppler effect is used to estimate approximate distances to stars and other celestial bodies. Using the same principle, lets say we divide an image (photograph) in pixels and that ...
1answer
85 views

### How Does Mean Centering Affect the Result of Using SVD to Compress Images?

I have been learning about using the Singular Value Decomposition to find low rank approximations to matrices. I had an image which I converted to a matrix. I regarded each row of the matrix as a '...
1answer
352 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 ...
1answer
44 views

### How to recognize for small video sequence with a large sequence?

I'm working on the idea of recognizing a small video sequence (a sequence of 18 seconds) within a long one (a sequence of 15 minutes), the first idea that come to mind stats that I have to ...
2answers
81 views

### Image Interpolation Using the Yule Walker Equations

I have been studying about the Yule-Walker equations for prediction of a time series data from knowledge of past values of the series. Is there any way I can use the same in an image to exploit the ...
1answer
105 views

### What is the meaning of the sum of kernel components in digital image filtering?

When analyzing an image signal as a series of Dirac impulses in the continuous spatial domain, I applied continuous low pass filters (to reconstruct or smooth it) with area equal to 1 to preserve the ...
2answers
145 views

### How would you interpret the pattern in this picture? (generated by re-sorting pixels based on their RGB value)

Was playing with some pictures and ran the ruby code below. The code reads an input image using the ImageMagick library, gets an array of pixels, re-sorts the pixels and then writes out an image with ...
1answer
1k views

### Why a Convolution Matrix Is Called a Kernel?

According to Wikipedia: In image processing, a kernel, convolution matrix, or mask is a small matrix. I am wondering, why the matrix is called a kernel? Does it has anything to do with kernel ...
1answer
555 views

### In Plain English, What 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 "...
1answer
146 views

### Given a Horizontal Derivative Kernel What Would Be the Output Image?

Hi, im solving this problem and everything went well until i went and solved the position p(5,3) and i got the answer of 0. However, the solution guide lists the solution as 150 which is pointed at ...
3answers
1k views

### The Effect of a Kernel on an Image By Filtering

I am going through an old exam paper and trying to understand this question where they ask us to tell them what effect the following image filter would have if its convolved with an image: ...
1answer
18 views

### What is the difference between positive matrix coefficients and negative matrix coefficients of an audio?

I have turned an audio file into an one dimensional array by using audioread function in matlab and found several positive and negative fractional coefficient values.What is the basic difference of ...
1answer
50 views

### How can I detect the tree rings?

I'm looking for the way to detect the tree rings automatically in the wood dist image. Using the matlab, I have removed the background, and binarized the image. How can I detect the white and black ...
1answer
230 views

### Facing problem in plotting histogram of DCT coefficient of an image

In digital image forensic, it is assumed that the histogram of DCT coefficients of the un-compressed natural image has the smooth histogram. However, the histogram of DCT coefficients of the ...
1answer
73 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 ...
3answers
69 views

### Calculating the numerical gradient of a volume in one direction at a time

I want to calculate the gradient of an image volume in one direction at a time. Using the built-in function of Matlab gradient() I can get the ...
0answers
33 views

### Fast and Slow motion video detection using Optical Flow

I'm trying to calculate a "video motion" value in a given video sequence, meaning how fast or slow motion the video is. For instance, if a video is about a car racing, the value is high. Whereas if ...
2answers
338 views

### Chroma key algorithm with unknown background color

Suppose that I have an image with a foreground subject and a monochrome background. The image is a real world picture so the pixels belonging to the background do not share the same exact value. I ...
2answers
197 views

### Scratch Detection On Noisy Textured Surface

I wish to extract long thin scratches from the noisy background image.I have tried several ways such as stacking smoothed image with input image to remove some of the noisy background patch before ...
1answer
65 views

### What is meant by product of two images?

I would like to compute the product of two images. I tried with the code below. But the result is not like I expected. Can you tell me where is the problem in my code? https://ibb.co/Njc8w3b ...
0answers
57 views

### Implementing rotation in frequency domain and map it back to spatial domain

Please consider the following small example: ...
0answers
10 views

### What are the Red-Black Wavelets transformation for color (RGB) images?

I am looking for Red-Black Wavelet transform implementation on internet but I am unable to find it. Or How wavelets can be used for Images. Please help if you know how wavelets can be used for images.
0answers
21 views

### How to make ground-truth image for document image binarization task?

The two images are from DIBCO (Document Image Binarization Contest). The objective is to find a solution to binarize the top image (original image) to be similar to the bottom one (ground-truth image)....
2answers
69 views

### Digital Image Processing Textbook with Specific Topics

I am looking for a Digital Image Processing and analysis textbook, but there are specific topics that I would like the book to cover. Among other topics, I would like it to include a discussion of: (...
0answers
19 views

### Image processing and object detection in sales force automation

We have a specific requirement in our sales force automation product. Requirement in merchandising module There is one shelf check activity in merchandising where salesman is capturing which ...
0answers
9 views

### Logical Steps to segmenting Lung Fissure Structures

I am given the task to do the Lung Major Fissure Segmentation in a CT image to find it's position in an image. This is what a Major Fissue looks like: https://www.med-ed.virginia.edu/courses/rad/cxr/...
1answer
39 views

### morphological processing : Hit or Miss shape detection

I am currently looking at shape detection for Hit or Miss. I am having a bit of trouble with the concept of the window that they have you to detect the shape. Up till now reading about hit or miss ...
0answers
16 views

### need tool to identify most focussed image in a series

I have a situation where I am sent a series of photographs of hand-written documents (quite old, from 1850-s). Each photo is done just as you and I would photo a page from a book, so not a ...
2answers
53 views

### Transforming RGB images including NIR to LAB

I'm relatively new to image processing, so I hope I don't ask trivial questions. I have some images that I want to use in a machine learning context. The images have four color channels: RGB and NIR (...
1answer
91 views

### What is the point spread function and optical transfer function and what uses are they in image processing

So I seem to really be struggling with the concepts of the point spread function (PSF) and optical transfer function (OTF) and what they are used for in image processing. Everything I seem to google ...
1answer
20 views

### Gender classification using Periocular Region [closed]

I have a dataset of the periocular region, I have images of the male and female periocular region but they are only labeled as left and right periocular region, Folder is a mixture of male and female ...
0answers
34 views

### Thermal image based segmentation [duplicate]

I'm working on a project to do segmentation of thermal images. So far, the methods have produced limited segmentation performance (k-means, Otsu's Method, Sobel, Canny, LoG). I am trying to achieve ...
0answers
7 views

### BRIEF feature vector random point sampling 3rd method

When using the BRIEF algorithm to generate a feature vector, 5 methods are provided for selecting 2 random points inside a feature point patch. The 3rd method is described as follows: Let consider ...
1answer
610 views

### What does Smoothness Prior mean in the context of image processing?

I can quote from an article: "The first category of methods, known as diffusion-based inpainting, introduces smoothness priors via parametric models or partial differential equations (PDE) to ...
0answers
21 views

### Removing striped noise from an image

I was just wondering if anyone could explain to me the approach one would take to removing striped noise from the fourier domain of an image. I was reading an article about MRI image from 1 just ...
5answers
467 views

### Auto Detection of Rotation Angle on Arbitrary Image with Orthogonal Features

I have a task at hand where I need to detect angle of an image like the following sample (part of microchip photograph). The image does contain orthogonal features, but they could have different size, ...
10answers
16k views

### Is deep learning killing image processing/computer vision?

I'm looking forward to enroll in an MSc in Signal and Image processing, or maybe Computer Vision (I have not decided yet), and this question emerged. My concern is, since deep learning doesn't need ...