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.

Filter by
Sorted by
Tagged with
1
vote
0answers
7 views

Size filtering on binary images

I have noisy images from which I extract the contours using OpencCV's findCountours, which performs binarization internally. This results in innumerable small ...
0
votes
1answer
12 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 ...
1
vote
1answer
28 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 ...
0
votes
0answers
8 views

Questions about Optical Flow implementations

I have some doubts related to some of the optical flow implementations. How to compute angular error for optical flow algorithms? I know the formula for computing, $\theta=\arccos(\vec{v}_c\cdot\vec{...
0
votes
0answers
11 views

Extract feature points and visualize on 3d Mesh

I'm Coding with python, I have a 3d Model mesh, and I'm trying to get features and descriptors So I was able to get Zernike moments using mahotas library which gives a vector of data, I have to ...
0
votes
0answers
10 views

What is the name and theory behind a basic motion filter with background update?

I am working on machine vision task. I am using openCV in Python. I need to detect motion. Best would be if I can calculate the difference between the new image and background. However, the ...
0
votes
0answers
4 views

can I combine 2 raster with wavelet transform in R?

I Have same problem, i will combine 2 raster data with wavelet fusion r1<-brick("mask data/r1_mask_black.tif") r2<-brick("mask data/r2_mask_black.tif")
0
votes
0answers
18 views

Detect Colors in an image using opencv python

How to find different colors present in an image? Is K means clustering enough or any other simple way of doing it using opencv exist?
0
votes
0answers
12 views

Kalman Filter in Vision - Constant Velocity Model - Units

Let's assume we have series of frames with a known object. I want to track the object using Kalman filter using constant velocity / acceleration models. My questions are: (i) Which model to use? CV ...
0
votes
0answers
26 views

Weight update in particle filters

For particle filtering weight update, often the transitional prior is used for the proposal density, in which case the weight update simplifies to just the likelyhood function. However, in one ...
0
votes
2answers
25 views

Camera image pixel structure origin

I am using machine vision for industry task with opencv. I have images from a camera monitoring the process. The detailed look at the small part of the image follows: Enlarged: In the detail, it ...
1
vote
0answers
26 views

drawing a line from where the tires meet the ground

I followed these steps to write a program in Matlab to detect the edge of the wheels where they meet the ground. Step 1. read the image Step 2. k-means segmentation Step 3. Dynamic binarization ...
-1
votes
0answers
12 views

Autocorrelation of vector of images

I have a set of images (think a ball getting bigger and smaller). I want to assess the periodicity in this string of images (each data point in my signal is an image). How can I go about doing this in ...
1
vote
2answers
32 views

Making sense of indices in 2D convolution operations

Referring to the answer here: https://www.quora.com/Why-are-convolutional-nets-called-so-when-they-are-actually-doing-correlations, the equation for a discrete 2D convolution is specified as: $$C(x,y)...
0
votes
1answer
23 views

How do I detect the sharp edges in the following image?

I am looking to count the sharp pointy triangular things in the image. However I was unable to do so. One approach I did try was take a convex hull of the contour and then find convex defects but it ...
0
votes
0answers
22 views

What is a low pass kernel [closed]

Can someone tell me some common features of a low pass kernel? I have tried looking it up but i cannot find anything.
-1
votes
0answers
23 views

Which noise reduction tecnique? [closed]

What is one of the most useful noise reduction techniques of filtering the Fourier space?
0
votes
1answer
16 views

Recommended approach for extracting specific edges from image?

I have several sets of images with a typical image being: and from each image, I would like to extract the top and bottom curves of the object, shown in red here: What are some possible tools I ...
1
vote
1answer
42 views

Outlined text extraction from image using OpenCV

I have some video frames I'd like to extract some text from (for making softsubs from hardsubbed video for learning). The text in question is mostly in Chinese script (some numbers and Latin letters) ...
1
vote
0answers
37 views

Robust custom watermark algorithms?

I'm doing research on image and audio watermarking, and so far I've read some literature in order to get basic introduction and good initial understanding of this topic. Right now I'm reading book "...
1
vote
2answers
29 views

The Gradient of Least Squares of 2D Image Convolution

Given the objective function: $$ \frac{1}{2} {\left\| h \ast x - y \right\|}_{2}^{2} $$ Where $ h $ is the 2D convolution kernel and $ x $ is the 2D convolution image and $ y $ is a given 2D image. ...
0
votes
0answers
14 views

Optical flow Horn & Schunck smoothness error

I was reading about the Horn & Schunck method and they define the smoothness error as (Robot Control 1988 (SYROCO'88): Selected Papers from the 2nd IFAC Symposium p. 348): $E_{sm} = \iint{\left(...
1
vote
1answer
24 views

What impact have different types of border-handling on high pass or low pass filtering?

When high or low pass filters are being applied to an (grayscale) image, the borders need to be handled separately. They could be filled with 0's or 255's (b/w), repeat the nearest pixel value, or ...
0
votes
0answers
4 views

Why can ARSS not recreate audio from a spectrogram without sounding muffled?

Why do ARSS and all audio to spectrogram then back to audio program's create audio files that sound muffled? I know their is some physics and math with the short-time Fourier transform and etc. I ...
0
votes
0answers
15 views

Find specific feature within an image / Neural Networks

i am working in the field of image processsing and we have a certain problem which is difficult to solve by rules-defined algorithms. Is it possible to teach a certain pattern into a neural network, ...
0
votes
1answer
23 views

Are there any efficient algorithm to detect circular shape of arbitrary size in an image?

I have images that are 1278 by 1024. They are pictures of a certain product that is rectangular in shape and are about 25mm by 20mm. As a part of a quality inspection process using computer vision, ...
1
vote
2answers
768 views

Career in signal processing

I am doing my MSc in electrical engineering, and there are not many courses in my university on signal processing. I want to develop my skills in signal processing such that I have a hold in one ...
1
vote
2answers
38 views

Definition of difference between compression and filtering

I'd like to explain the motivation. It sounds like a neuroscience topic but I am after the strict Signal Processing POV. (I don't come from a Signal Processing background). Interested to learn ...
0
votes
0answers
25 views

urgent: MRI calculations question

I have a biomedical imaging exam tomorrow and I'm struggling quite a bit with this question below (from b-d). I was hoping someone could help answer these questions or at. I'll describe my approach to ...
0
votes
1answer
14 views

Similarity or Relation between Walsh Hadamard Transform and Slant Transform

Is there any relation between Walsh Hadamard Transform and Slant Transform? Or is there any common property or similarity?
0
votes
2answers
44 views

Image Brightness on 2D Fourier Transformation

What effect does the brightness have on the frequency spectrum of 2D Fourier Transformation? Example. Suppose we have a gray image and calculate 2D Fourier Transformation. Then we increase the ...
0
votes
1answer
82 views

Amplitude demodulation of sinusidal signal in matlab

AM-demodulation task and I was asked to demodulate the signal in MATLAB and the result should contain three pictures. plotting the $fft$ the (frequency spectrum)of the signal i was able to determine ...
0
votes
1answer
19 views

Linear Panorama Transform

I am trying to create a linear panorama (a series of images taken from the same plane but not the same location and not rotated) but was not sure which transform is appropriate for this task. I know ...
1
vote
1answer
30 views

How to interpret PSNR value?

Say, I have original image, noised and denoised. By PSNR value I want to find out how good does my denoising algorithm works. For which pair of the images should I calculate it? I've tried it for ...
0
votes
1answer
25 views

MATLAB Image-Processing Toolbox: asking for a roadmap!

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 ...
1
vote
4answers
72 views

Apply Principal Component Analysis for RGB Images

I've implemented a method to compute PCA on grayscale images. I haven't seen PCA on RGB images yet, which left me wondering if it is possible to perform it. With RGB images, is PCA done for each ...
0
votes
0answers
7 views

Response function for digital camera pixel

To help me with doing some signal processing on an image, I'd like to model how a digital camera works. The camera has a bunch of pixels. What is the relationship between the value of that pixel in ...
1
vote
0answers
27 views

Recreating an image from random samples?

Assume that I have samples from an image, but the samples aren't on a grid, but instead there are multiple lowres versions of the original where the sampling locations are slightly jittered, so the ...
0
votes
0answers
32 views

Camera obstruction detection

I'd like to detect if camera view is obstructed (fully or partially) by some object (paper, hand, some device, etc). Do you know any good methods for this task? I've already experimented with: RGB ...
0
votes
2answers
37 views

What do the 1D filters represent when using imfilter?

I am reading the source code of an algorithm that is used to process an image. While reading this source code (and others), I've found lines of code of the form ...
1
vote
0answers
23 views

How to create 3D signed distance function?

I am trying to segment a 3D shape using levelset. I want to track shape movement in consecutive frames. Now I want to create a signed distance function matrix for ...
2
votes
0answers
31 views

How does the “additive operator splitting” exactly work?

I am reading about the non-linear (or non-homogenous) diffusion method (aka anistropic diffusion method). There are several ways of implementing this method. In all cases, we first need to discretise ...
0
votes
1answer
17 views

Why is the anisotropic diffusion equivalent to the heat equation when using a constant diffusion coefficient?

The anisotropic diffusion is defined as $$\frac{\partial I}{\partial t} = \mathrm{div} \left( c(x,y,t) \nabla I \right)= \nabla c \cdot \nabla I + c(x,y,t) \Delta I$$ where $\operatorname{div}$ is ...
0
votes
0answers
48 views

How can I calculate homography from the room height and camera calibration matrix?

EDIT2: I've added an assumption that the camera calibration matrix is given. Other factors (rotation, camera pose) are still not given. I want to measure actual lengths of floor edges (blue lines in ...
4
votes
1answer
156 views

Efficient implementation of 2-d circularly symmetric low-pass filter

How can a two-dimensional ideal circularly symmetric low-pass filter or its approximation be efficiently implemented on data sampled on a square grid? I'm referring to an ideal filter with a spatial ...
1
vote
2answers
58 views

What Is the Relation Between Deblurring and Deconvolution in Computer Vision and Image Processing?

The deblurring problem can be modelled as follows $$ f = \phi u + \epsilon, \; \epsilon \sim N(0, \sigma) $$ where $\phi$ is a filter (e.g. a low-pass filter) and $\epsilon$ is a Gaussian noise. In ...
1
vote
1answer
28 views

is there a use for a changing kernel in image convolution

I understand the principle of image convolution. Maybe. I think it is this: You use a small matrix with numbers in it, then take a sample of an image with as many pixels as you have numbers in your ...
1
vote
1answer
32 views

Why entropy value can be used as measure of contrast of an image?

I was looking for value that can measure a contrast of an image. And I found a couple of answers like this one https://stackoverflow.com/questions/13397394/how-to-measure-contrast-in-opencv-visual-c/...
0
votes
0answers
54 views

What are the limitations of Watershed Segmentation Algorithm?

I am developing an Android application using Opencv to detect objects from images. I used Canny edge detector to detect the edges and extract contours, and it's working good so far. But I need to ...
0
votes
1answer
39 views

OpenCV warpPerspective implementation

I've implemented the least squares method to find the homomorphic image to fix the rotation and projection in an image. Now I'm trying to implement the OpenCV warpPerspective method in order to "fix" ...