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Questions tagged [downsampling]

231 questions
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fast downsampling of huge matrix using python (numpy memmap, pytables or other?)

As part of my data processing I produce huge non sparse matrices in the order of 100000*100000 cells, which I want to downsample by a factor of 10 to reduce the amount of data. In this case I want to average over blocks of 10*10 pixels, to reduce…
Gert
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ghostscript downsampling of pdf images, downsample factor error

I issue the following command: gs \ -o downsampled.pdf \ -sDEVICE=pdfwrite \ -dDownsampleColorImages=true \ -dColorImageResolution=180 \ -dColorImageDownsampleThreshold=1.0 \ And get the following errors: Subsample filter does not support…
Admiral Tso
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Max-pooling vs. zero padding: Loosing spatial information

When it comes to convolutional neural networks there are normally many papers recommending different strategies. I have heard people say that it is an absolute must to add padding to the images before a convolution, otherwise to much spatial…
Daniel Falk
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How we can down sample a 1D array values by averaging method using float and int window sizes?

I am trying to down sample a fixed [Mx1] vector into any given [Nx1] dimensions by using averaging method. I have a dynamic window size that changes every time depending upon the required output array. So, in some cases i get lucky and get window…
Nomiluks
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C++ How to best scale image by dropping pixels

I am capturing a frame of data from an imager with a resolution of 102 x 77. I want to downsample this to 80 x 60. Quality is not the main concern but ease of implementation and speed are. I believe I can accomplish this by roughly dropping every…
PhilBot
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How to downsample a texture

(I'm doing this in Apple Metal, but I think the question applies to OpenGL and DirectX too. Code examples from Metal or OpenGL are highly welcome.) I have one texture smallTex whose size is a multiple of the size of another texture bigTex. For…
Jonas Sourlier
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Downsampling a 2d MATRIX in matlab, by taking average block wise

Say I have a matrix A, which is of dimension 4x4. Now I want to downsample this matrix by a factor 2 to get a new matrix B of dimension 2x2. I want to downsample in the following way : Let A be 1 5 9 13 2 6 10 14 3 7 …
Adithyan Ilangovan
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How to simply downsample a triangular mesh?

This requirement occur when I show the surface mesh in Matlab by trisurf, because the mesh is dense (high-resolution) and it is rendered slowly and can not be rotated. So I am wondering there is some intuitive method to downsample the mesh while…
nicozuo
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Downsample PCM audio 44100 to 8000

I've taken over maintaining an android application that records an audio source using AudioRecord in 44100, 16-bit mono. I need to downsample it to 8000. The current app has a downsample algorithm in it that I'm not sure is working correctly. …
mjsalinger
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How does OpenTSDB downsample data

I have a 2 part question regarding downsampling on OpenTSDB. The first is I was wondering if anyone knows whether OpenTSDB takes the last end point inclusive or exclusive when it calculates downsampling, or does it count the end data point…
Classified
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Downsampling 96 to 44.1 kHz audio fast (realtime) in a VST instrument

I'm trying to make a fast downsampling function in my VSTi (c++), but I'm having some hard time to get it to work. This is what I have and what I'm trying to do. First off is the low-pass filter.. void resetFilter() { c = 1.0 /…
Magnus
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GLSL 330: down sample texture

I want to down sample an input texture from 800x600 to one quarter itself (200x150 pixel). But if I do that I can see only a little bit of the image. It seems that the frament shader doesn't down sample the whole texture. The following example is to…
Tobias
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Ghostscript: how to reduce file size of large PDFs without changing smaller PDFs

I am using GhostScript to convert large batches of PDF to PDF to reduce file size. The original PDFs vary in size and quality. Where there is a low quality, small file size (<350kb) PDF the output from Ghostscript is often poor. Is there a way I can…
vix
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Downsampling: Audible Clicks

In a C++ Program, I am trying to downsample blocks of 8192 audio samples (-32768...32767). The original Sampling Rate is 48kHz, and I'd like to have 16kHz. The ratio 16/48 should yield roughly 2731 samples if the original number of samples is…
Nox997
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Python - Downsampling of a list of points, with given coordinates and distance between two adjacent points in the list

I really hope someone can help me with this! I'm trying to make this script run as I want, but I cannot seem to get the hang of it. The file with the data to be handled is input from a GPS and looks like this: Line…
user1059822
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