# Questions tagged [image-processing]

This tag is for the mathematics involved in the field of image processing. Many such questions are also appropriate for Signal Processing Stack Exchange.

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### How can I write graham scan algorithm in C# without using pre-written library?

I am trying to write the Graham Scan algorithm but I do not understand how I can write it without using pre-written library. I am researching this for a long time but I really could not find any ...
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1 vote
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### Integer algorithm to rotate a bitmap image(2d array) on small angle?

The task is - if you want to rotate a bitmap image on the small angle , so the most of the pixels will remain on its place or will be just shitted strict horizontally or vertically a little bit, is ...
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### Hough voting or RANSAC voting, which strategy is better for pixel-wise object's center location estimation?

If we know all the pixels of the object in an image and draw a unit vector from all the known pixels of the object body towards the center direction of the object, and then apply some voting ...
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### Matching nodes by comparing overlapping subsets of a graph

For an image stitching algorithm, I am trying to match keypoints of a moving object in multiple images. I thought one way to do it is to create a graph of the keypoints in the image and compare the ...
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1 vote
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### Finding object position using calibrated camera and object size

I have a calibrated camera. In other words, I calculated the extrinsic and intrinsic parameters as below using opencv (more info)...
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### Least square fit of ellipse worsens with increasing border thickness

I use the least square method to fit ellipses to data points that originate from a binary image. The least square fit minimizes the sum of squared algebraic distances between data points and the ...
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### 2d convolution in analytic form

I have an image of a 2D-sinusoidal pattern $f(x, y)$ with wavelength $\lambda$ which I would like to convolve with a 2D circular pill-box function $h(x,y)$ of radius $r$. The image is given by  f(x,...
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### A proper definition for homogeneous coordinates in geometric image formation

In my computer vision course, we apply homogenous coordinates to represent points in 2D or 3D space. However, in my course it lacks a proper definition of what homogeneous coordinates are. I have ...
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### Conflict for solving denoising problem as optimization problem by gradient descent method

I am new to image processing and optimization. Let y be a noisy image described by the relationship y = x+n, where u is a noise-free image and n is the noise. The goal is to recover x from n. min || y-...
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### How can I calculate all possible combinations between a specific ratio range?

Not sure this is the right wording for this sort of problem, but let me explain by context. Instagram displays specific image ratios when posted to a feed. These ratios are: 1:1 (square) 1.91:1 (...
1 vote
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### Jacobian Calculation with Homographic Coordinates

I'm trying to work my way through an image processing paper (Creating Full View Panoramic Image Mosaics and Environment Maps) and am stuck on how the Jacobian is calculated, especially terms (\$J_{17}, ...
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