Questions tagged [image-processing]

For questions related to the collection, processing and interpretation of pixel data from imaging systems.

3
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1answer
36 views

Poisson image blending artifacts

I am trying to implement Poisson image blending as in the paper Poisson Image Editing. This is the task of filling in a masked region of an image by minimizing $$\min_f\int_\Omega \left | \nabla f - \...
2
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0answers
24 views

Cell-segmentation from overstaining images Ask [closed]

I am currently trying to segment cells from digital pathology images. The method I use is an algorithm based on color distance. This works for most of the cases, however, when dealing with the images ...
2
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1answer
39 views

Algorithm to determine flat surfaces and camera orientation without specialized hardware

Modern augmented reality platforms such as Google's ARCore and Apple's ARKit seem to only operate on mobile devices, I'm guessing, because their underlying algorithms require specialized hardware that ...
0
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0answers
14 views

Finding Duplicate Pixel/Objects along Image seams

I have a seam of two images joined by merging algorithm that on occasion generates duplicated pixels/objects/artifacts on both sides of the seam. The images are large and currently the seams are ...
2
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0answers
77 views

Find points that form curve segments in a point cloud

I have an ultrasonic image represented by a point cloud as shown below: I need to extract features from this image. These features can be easily recognised by a human brain since they form continuous ...
1
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0answers
32 views

How to numerically transform a 2D Fourier spectrum with arbitrary frequency shift to center frequency?

Suppose $F(u,v)$ is the center frequency Fourier representation of some $f(x,y)$ in 2D. $$ f(x,y)=\int\limits_{-\infty}^{\infty}\int\limits_{-\infty}^{\infty}F(u,v)e^{2\pi i (xu+yv)}dudv $$ In ...
2
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2answers
62 views

Is there an efficient algorithm for matching objects in one image to objects in another?

Suppose I have two images that contain many objects that are identical, or nearly so. Specifically, say the objects are shifted and scaled, but by differing amounts, from one image to the other. Is ...
2
votes
1answer
63 views

Polygon approximation with a circle

There is an article describing how to detect a pupil from an eye photo. A.-H. Javadi, Z. Hakimi, M. Barati, V. Walsh, and L. Tcheang, "SET: a pupil detection method using sinusoidal approximation," ...
3
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2answers
158 views

Image hash similarity matching possible?

I have the following question: We have two face image files (JPEG), a Matrix of $128\times 128$ with values between 0-255. We would like to hash both image files using a function $f(x, key)$. Where I ...
1
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0answers
81 views

computing dual matrix trace norm and tensor gradient in python

I'm trying to write the following function in python: $$ f_\mu(\mathcal X) = f_0(\mathcal X) + \sum_{i = 1}^n \max_{||\mathcal Y_{i(i)}|| \leq1} \alpha_i\langle \mathcal X_{(i)},\mathcal Y_{i(i)} \...
3
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0answers
112 views

Methods to implement floor dirt detection algorithm

I'm trying to detect dirty floor areas in a series of images, using MATLAB and its Image Processing Toolbox, like the one that follows: In the image above, there are two distinct areas, the whiter ...
3
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0answers
209 views

Open source implementation of Multiscale Combinatorial Grouping

I would like to use Multiscale Combinatorial Grouping for my PhD research. However, I am restricted to use open-source implementations and this one runs on Matlab. Does anyone know of an equivalent ...
1
vote
1answer
427 views

Iterative camera calibration - No convergence

I am trying to implement the algorithm from the research paper "Accurate Camera Calibration using Iterative Refinement of Control Points" from Datta et al. Running many iterations does not show a ...
0
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2answers
84 views

Which image filter acts like “surface tension”?

I'm looking for an image filter that does the following operation: In my first image, I have two spheres. After applying the filter, I'd like to have them "glued together" which something that kind ...
1
vote
1answer
38 views

Filter coefficients for convolutional inpainting

I'm working on a project that requires unknown image elements to be filled in, and am using a simple inpainting algorithm, which I would like to understand better. It works by repeatedly convolving a ...
0
votes
2answers
79 views

Which technique to use for signal/image processing or noise removal?

I have an image that looks like this (it might appear low res in a browser because it is 16 MB). This image was taken with a scanning electron microscope, but because the equipment is outdated there ...
1
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0answers
74 views

Can x-ray back-projection be converted to hard-field magnetic induction tomography?

This is a question about hard-field back-projection as used in x-ray tomography, applied magnetic induction tomography. Al-Zeibak and Saunders have shown that x-ray filtered backprojection can be ...
2
votes
2answers
444 views

Finding intersections of curves in a binary image

I am trying to find the intersection points in images like the one posted below. The intersections I'm trying to find are circled in red in the image below it. My most succesful approach: Thin the ...
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0answers
45 views

Mathematical physics applications in present-day image processing

During the past few years several important areas of image processing and image classification or generation became dominated by convolutional neural networks. I'm interested if there are any methods ...
0
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1answer
70 views

Is the inverse radon transform considered a linear operation?

I wanted to know if practically the inverse radon transform operation is considered linear and would be a good candidate for the application of compressed sensing. To my understanding it should be ...
1
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0answers
145 views

Integral image resizing

I'm trying to find an approach for integral image resizing. I found out that I can do it with a bilinear interpolation method, but with this approach I can only resizing by the factor which is a power ...
0
votes
1answer
36 views

Is there a common way to decribe voxels and greyvalues in formulars

I need to write a report about some image processing topic. I want to describe some kind of density, e.g: $\rho = \frac{\text{voxels with greyvalue 128}}{\text{number of voxels}}$. Is there a common ...
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0answers
158 views

How to obtain projections from sinogram in ART reconstruction technique?

I'm kind new in the Computed Tomography field and I'm trying to understand and implement ART technique. Said it, I started to read the book The Mathematics of Medical Imaging - A Beginners Guide by ...
1
vote
1answer
105 views

What is a good algorithm, and framework, to calculate centres of gravity or mass (cog)?

I'd like to take an photograph, subdivide it into a tesselation, either of squares, or (ideally), hexagons, and then find the centre of gravity (or, if you prefer, centre of mass) of each cell of the ...
1
vote
2answers
59 views

Automatic motion recognition

How difficult is it to program an automatic software using C that is able to read astronomy images of up to 4096x4096 pixels (or other sensor geometries), search ...
2
votes
2answers
449 views

Fitting rectangle to segments in image

I have the task to fit a rotated rectangle of known size into an image like This is a synthetic test case, in the real application, everything is rather blurred. The rectangle has to cover as much ...
1
vote
0answers
66 views

Convolutional Neural Nets for Large Scale Image Classification on Windows?

I need to build some CNN's using very large numbers of photos, to classify which photos contain certain features. I've run into a number of road blocks. As much as I love both Linux and ...
1
vote
1answer
62 views

What are the most popular wavelet or tight frame regularizers for image reconstruction problems?

A common approach to image reconstruction is to solve the convex optimization problem \begin{equation} \text{minimize} \quad \frac12 \| Ax - b \|^2 + \gamma \| Dx \|_1 \end{equation} where $b$ is a ...
6
votes
2answers
2k views

discrete definitions of curl $\nabla \times F$?

I have some data defined in an array (an image) and I need to find the curl of a certain function. Wikipedia has an integral definition of curl that I like, maybe it can be discrete. $$ \nabla \...
6
votes
1answer
460 views

Open Source MRI Image Stacks

I'm working on a voxel-based modelling application and one of the features that I've implemented is a method to do a 3D mesh reconstruction from a series of 2D image slices (similar to an MRI). I've ...
3
votes
0answers
92 views

FFT-based Image Rotation Algorithms More Accurate Than Chirp-Z?

We're currently using a Chirp-Z based implementation: R. W. Cox and R. Tong, "Two- and three-dimensional image rotation using the FFT," IEEE Trans. Image Processing, vol. 8, no. 9, pp. 1297–1299, Sep....
3
votes
2answers
210 views

How to separate text from the paper on a black and white page?

I tried to discretize an image into black and white and came into some difficult. The difference between the letters and paper is pretty clear to our eyes: However a simple thresholding trick doesn'...
1
vote
1answer
511 views

Calculate the area and perimeter of a hand-drawn shape

I need to know whether my idea for my final year project could be achieved or not. If its achievable please guide me with the relevant language and other frameworks. The idea I have a piece of paper ...
3
votes
2answers
217 views

What are the numerical methods for testing for dissimiliarity between image based probability histograms?

I have several probability distribution histograms of images that I am comparing to test for dissimilarity. Each histogram has 256 bins, the bins are common for all histograms. The images are taken ...
3
votes
1answer
102 views

Estimating Regions of Flow in Grayscale Video

I am looking to find an algorithm/method by which I can detect regions of flow in a video. The video is that of a grayscale heatmap where the majority of the image is not in motion. The areas that are ...
1
vote
1answer
178 views

Compare reconstruction of matrices using SVD

I'm interested in how much 'signal' is retained from including k singular values in a Singular Value Decomposition, but I'm having trouble conceptualizing (or ...
0
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0answers
135 views

1D fit on a surface in matlab

I have a problem fitting a $N\times N$ ($32\times 32$ in this case) matrix in Matlab. Here is the deal I have this image, and I want to create 1 dimensional fit between the points and then be able ...
1
vote
1answer
659 views

Convert Image of Map to 2D Grid in Python

I have this map showing the geography of Europe (below), and I wish to convert it to a matrix in python that would be a 2D approximation of this image where 0's would represent the ocean and 1's would ...
3
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0answers
176 views

Shape measure for C-shaped objects

There are many well defined measures for many basic geometrical objects such as rectangularity (area coverage of minimum bounding rectangle), triangularity (area coverage of minimum enclosing triangle)...
1
vote
1answer
211 views

Natural spline conditions for 2D cubic splines

I am currently working on 2D interpolation and I am using cubic splines. In 1D given N points one would use N+2 splines and would have to apply additional constraints in order to achieve a square ...
1
vote
1answer
110 views

Is it possible to locate an image in a video using MATLab?

I'm not a huge programmer, but if it'll save me lots of time, that's when I code (given that it's possible). I know MATLab has a Computer Vision Toolbox, so my question is: is it possible to program ...
3
votes
0answers
111 views

Creating FEM mesh for image region — what is the most suitable shape function?

I wish to create a FEM mesh to solve an inverse elasticity problem, for an irregular domain. This domain is given by a medical image, so it is discretised and each square on the grid has one scalar ...
0
votes
1answer
67 views

How can we compute the exact value of some rotational symmetric n-by-n convolution kernel

The commonly used $3\times 3$ Laplacian convolution kernel $\frac{1}{6}\begin{bmatrix}1 & 4 & 1\\4 & -20 & 4\\1 & 4 & 1\end{bmatrix}$ is only an approximation of rotational ...
1
vote
1answer
50 views

What is a general method for identifying how connected parts of a binary volume are?

I have a binary volume consisting of a number of disconnected objects. (coming from a noisy, anatomic dataset) However, some of the objects are 'somewhat' connected. Picture a big cylinder and a ...
0
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0answers
191 views

Histogram separation energy equation based on Bhattacharyya

I am working in level set method, specially Lankton method paper. I try to implement Histogram Separation (HS) Energy problem (Part III.C). It based on Bhattacharyya to control the evolution of ...
3
votes
2answers
280 views

Cloud solutions for microscopy image analysis

At our research facility we routinely perform what are called PALM (Photo-activated localisation microscopy) or STORM (stochastic optical reconstruction microscopy) experiments. You can read all ...
1
vote
1answer
462 views

How to minimize the artefact of a cartesian to polar transform followed by a polar to cartesian transform?

I'm transforming cartesian images into polar images. (x,y) => (angle, radius) I fill the polar image by iterating on each of its pixels and filling them by doing the reverse polar transform. For a ...
1
vote
2answers
595 views

Intel's OpenCL SDK for image processing

I'm working on an image processing project and have written some of my algorithms in OpenCL. At the moment I'm using Cloo. I'm at the stage now where I want to optimise my program, as it currently ...
0
votes
1answer
60 views

Behaviour of folding matrix on image borders (Gaussian Blur)

In one step of image evaluations I need to apply a gaussian blur to pixel data. I do this by folding each pixel with a gaussian folding matrix. This is no problem unless I try to do this with pixels ...
1
vote
1answer
559 views

What is Precision-Recall Curve? [closed]

I have a data mining assignment where I make a content-based image retrieval system. I have 20 images of 5 animals. So in total 100 images. My code returns the 10 most relevant images to an input ...