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Questions tagged [lanczos]

25 questions
24
votes
5 answers

Android: Bitmap resizing using better resampling algorithm than bilinear (like Lanczos3)

Is there any way or external library that can resize image using Lanczos (ideally) or at least bicubic alg. under Android? (faster is better of course, but quality is priority, a processing time is secondary) Everything what I've got so far is…
Jolinar
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1 answer

Image 2x downsampling with Lanczos filter

I'm trying to implement image downsampling with Lanczos2. However, the kernel seems to have zeros everywhere (since sin(pi*x)=0 if x is integer) except at the center pixel. Thus, if the downsampling factor is an integer number (e.g. the output size…
Yoav
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3
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0 answers

implicitly restart Lanczos method

I want to write simple toy code for implicitly restart Lanczos method. Without implicit restarting, the code is perfectly working but when I turn on the restart, I cannot get proper solution To my knowledge, newly constructed w should be orthogonal…
SungHwan Choi
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3
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1 answer

Simple Lanczos algorithm code to obtain eigenvalues and eigenvectors of a symmetric matrix

I would like to write a simple program (in C) using Lanczos algorithm. I came across a Matlab example which helped me to understand a bit further the algorithm, however from this piece of code I can't find the way of getting the eigenvalues and…
Manolete
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2
votes
1 answer

Eigenvalue Probem

I'm trying to diagonalize a matrix in julia, but the matrix is itself too large to calculate. But I can efficiently calculate the matrix vector product. I'm looking for a solution so that I can use the matrix vector product into eigs and solve using…
Gaurang Parkar
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2
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1 answer

Lanczos SSE/AVX implementation

Does anybody have any tips on how to implement Lanczos image resampling (upscaling and downscaling) algorithm using SSE/AVX (either intrinsic functions or assembly)? I looked on some C implementations but there is lot of branching and I don't really…
David Novák
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2
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1 answer

Delphi Fast(er) Lanczos resample

I'd like to find some code for a very fast bitmap resampling using Lanczos filter. Currently using this: http://pastebin.com/JxuqLXB9 I've been looking for a faster implementation, to no avail. Tried some implementations from GraphicsEx, Graphics32,…
hikari
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1 answer

How can I implement Lanczos resampling after every canvas transform without having to make a new canvas?

UPDATE: Once I got this demo working... holy smokes, it's SLOW, like 12-16 seconds for only a level 2 render (when image is around 1000x2000 pixels). This is not even worth bothering with. I found this really awesome and hopeful looking code in the…
CloudMeta
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1
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0 answers

Implementing the Lanczos algorithm into C++ for a quantum anharmonic oscillator

Firstly, I would like to mention that I am a complete beginner when it comes to coding, let alone C++, so bear with me, as I need complete guidance. My task is to implement the Lanczos algorithm for the case of a 1-D anharmonic oscillator in C++,…
Cia
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1
vote
2 answers

How to Pass a Large Data Set to a Function Without an Argument in C

I'm trying to create a general Lanczos algorithm that takes in an operator (function pointer) and prints a certain number of eigenvalues from that operator in C. I'm using the GNU Scientific Library to handle vectors and matrices. Specifically, the…
PaulPhy
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0 answers

LANCZOS interpolation in OpenGL

Is it possible to implement LANCZOS interpolation on the GPU in OpenGL for android or would you say it is a task for OpenCL? Time performance and device support are important issues. Best regards, David
David
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1 answer

How can I fix a Core Image's CILanczosScaleTransform filter border artifact?

I want to implement an image downscaling algorithm for iOS. After reading that Core Images's CILanczosScaleTransform was a great fit for it, I implemented it the following way: public func resizeImage(_ image: UIImage, targetWidth: CGFloat) ->…
Dirty Henry
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1 answer

SIMD-exploiting implementation of Peterson and Monico's Lanczos algorithm over the field with two elements

(This question is probably flirting with the "no software recommendations" rule; I understand why it might be closed). In their paper F_2 Lanczos revisited, Peterson and Monico give a version of the Lanczos algorithm for finding a subspace of the…
gspr
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1 answer

Rough Edges With Lanczos Resampling in Golang

I've been writing some basic methods to resize images in Golang. I've seen several posts about resizing images, but for the life of me I can't figure out what I'm missing... Essentially, my issue is that when resizing an image in Golang, my results…
Anish Goyal
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2 answers

Lanczos scale not working when scaleKey greater than some value

I have this code CIImage * input_ciimage = [CIImage imageWithCGImage:self.CGImage]; CIImage * output_ciimage = [[CIFilter filterWithName:@"CILanczosScaleTransform" keysAndValues: kCIInputImageKey, input_ciimage, …
Logioniz
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