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Questions tagged [back-projection]

The back-projection step can be visualized as a set of rays with base ad−1 and which are extended from projections The value of a voxel on the grid of the reconstructed structure is the sum of the ray values which intersect the voxel.

The back-projection step can be visualized as a set of rays with base ad−1 and which are extended from projections The value of a voxel on the grid of the reconstructed structure is the sum of the ray values which intersect the voxel.

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Save tensors as images in TensorFlow

This might be a simple question. I am just trying to do radon transform of an image and save it using functions in TensorFlow. But the result is not right. I know I can use plt.imsave() to save the image correctly, but I want to know how to do it in…
ddxxdds
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Implementing a filtered backprojection algorithm using the central slice theorem in Matlab

I'm working on a filtered back projection algorithm using the central slice theorem for a homework assignment and while I understand the theory on paper, I've run into an issue implementing it in Matlab. I was provided with a skeleton to follow to…
2fly2try
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Qualitative and Quantitative analysis of filtered back projection / iradon in matlab

I was wondering if anyone encountered this issue. I can reconstruct images from matlab that resembles the original image, however, the actual values are always different. For example, original image have values in the matrix ranging from 0 to 1,…
Tofo
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Issue with BackProjection and Opencv

I am trying to implement a backprojection algorithm with opencv to detect hands. This algorithm is composed from multiple sources. I have tried multiple methods such as morphologies and adding backgroundSubtraction to the projection to try to get a…
dylan7
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MeanShift formula understanding

I'm implementing MeanShift algorithm for object tracking, using ideas from here: http://www.cse.psu.edu/~rtc12/CSE598C/meanShiftColor.pdf Now I have backprojection image for consequent frame. Each pixel in such image marks the probability of…
olha
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OpenCv RGB Histogram Back-projection not working as expected

I use backprojection to locate a person in an image knowing the person's histogram. The issue is that it is not working on skin or on clear clothes. Here is what I get : Back-projection result Here is the code I use to compute the BGR histogram of…
Mai Kar
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CamShift only tracks object sometime, even though BackProjection is very good

edit: it seems like the side of the frame the object enters from matters. Not sure why it would, but entering from the right it always get picked up, from the top, it never does, until it gets close to the right side. In short, I'm trying to track…
cirea22
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How to determine point's 3D coordinates in a 3D triangle with knowing it's 2D coordinates

I have this code in a VB Class which converts a 3D point to 2D point to draw on screen: Dim N As Point3D, Triangle As Point3D N.X = 20: N.Y = 30: N.Z = 40 For I = 0 To 2 With N ZX = .X * CosZ - .Y * SinZ - .X ZY = .X * SinZ +…
Abuzanona
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Failure in coordinate transformation for projecting global position in camera coordinate frame

For a project I'm working on I have written a function which should take position and rotation in global coordinate frame of a robot and a camera, and project the postion of the robot into the camera coordinate image pane. The intrinsics of the…
Chris
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Filtered BackProjection Matlab

I have already implemented the code for BackProjection and it works. Now I have to implement the code for the filtered version, using first ramlak filter and then hamming window. My sinogram has dimension 144x180. My idea is…
Edoardo De Gaspari
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Implementation of Landweber iteration for dynamic Radon Transform in MATLAB

I am working on Dynamic Inverse Problems and Radon transforms. By the term "Dynamic," I mean the object (which eventually I am going to reconstruct its image by having the its measurements), deforms as time evolves. You may imagine the Heart or the…
Siamak Rabienia
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Why iradon returns negative pixel values?

I took 200 projections at a step angle of 1.8 degrees using LabVIEW software. The size of the image is 2748 x 2748 pixels, uint16. Then using Matlab, I load the projection images, do the flat field correction, resize the image by 1/3 and save the…
user8443638
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2D edge to 3D modelspace via glm::unproject - ray not intersecting with model

I try to do ray picking with collision, which means a 2D position on the screen is transformed into a 3D position in model space. My problem is, that the ray doesn't always intersect with the model to result in a valid 3D position. Here's what I…
Michael
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Edge orientation histogram back projection

I am working on an object detection module using opencv , and I am using the "Edge Orientation Histogram" as the object descriptor. after generating the histogram, I back project it onto the original image (after calculating the orientations in it…
Islam Alaa
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