delphi - Convolve function: Apply different radius in Gaussian filter -

-

there convolve function in swissdelphicenter.ch, set kernel , resulting image blurred, there no parameter apply more blur unless call function multiple times (not desired coz of performance issue).

how apply more blur image radius parameter in photoshop gaussian filter?

i using kernel apply gaussian filter:

1    2    1
2    4    2
1    2    1

you can make larger gaussian kernel - 5x5, 7x7 etc. performance decrease proportional size^2. kernel size faster use approach fft-based convolution.

edit
fft-based convolution: have data array a, array kernel values k (same length, zero-padded). 

conv(a, k) = backfft (fft(a) * fft(k))

to make convolution, 1 can

find fourier transform of data find fourier transform of kernel multiply them element-by-element (note numbers complex) make inverse fourier transform of product real part of

look @ fast convolution algorithms section in wiki , part 13.1 of numerical recipes (almost practical manual)

if interesting in fast treatment of many images, i'd recommend use dedicated library. example, opencv fast (delphi wrapper exists 2.4.11 version), graphics32, imageen etc.


Comments

Post a Comment

Popular posts from this blog

c++ - llvm function pass ReplaceInstWithInst malloc -

-
#include "llvm/pass.h" #include "llvm/ir/module.h" #include "llvm/ir/function.h" #include "llvm/support/raw_ostream.h" #include "llvm/ir/legacypassmanager.h" #include "llvm/ir/instrtypes.h" #include "llvm/transforms/ipo/passmanagerbuilder.h" #include "llvm/ir/irbuilder.h" #include "llvm/transforms/utils/basicblockutils.h" using namespace llvm; namespace { struct replacepass : public functionpass { static char id; replacepass() : functionpass(id) {} virtual bool runonfunction(function &f) { allocainst* insttoreplace = ??? basicblock::iterator ii(insttoreplace); replaceinstwithinst(insttoreplace->getparent()->getinstlist(), ii, new allocainst(type::int32ty, 0, insttoreplace)); return true; } }; } char replacepass::id = 0; static void registerreplacepass(const passmanagerbuilder &, legacy::passmanagerbase &pm) { pm.add(new re
Read more

java.lang.NoClassDefFoundError When Creating New Android Project -

-
i've tried installing (and re-installing) android studio several times now, , each time, studio isn't able create new android project. when attempt initial android studio window (ie. basic 'create', 'open', 'import' etc options), i'm asked of questions in wizard, brief progress dialog, followed nothing @ all. if open incomplete project process creates choosing 'open' list, can try choosing create new android project menu. this has same issue, error message in output console time... java.lang.noclassdeffounderror: com/sun/xml/internal/bind/v2/model/annotation/annotationreader (wrong name: com/sun/xml/internal/bind/v0/model/qnnotation/annotationreader) note: when installed android studio, installed incompatible jdk (1.8, not 1.7). have had go default project settings change jdk uses 1.8. does know how can avoid this? there place should downloading jxb classes? missing in java paths? this appears have been caused cor
Read more

Decoding a Python 2 `tempfile` with python-future -

-
i'm attempting write python 2/3 compatible routine fetch csv file, decode latin_1 unicode , feed csv.dictreader in robust, scalable manner. for python 2/3 support, i'm using python-future including imporing open builtins , , importing unicode_literals consistent behaviour i'm hoping handle exceptionally large files spilling disk, using tempfile.spooledtemporaryfile i'm using io.textiowrapper handle decoding latin_1 encoding before feeding dictreader this works fine under python 3. the problem textiowrapper expects wrap stream conforms bufferediobase . unfortunately under python 2, although have imported python 3-style open , vanilla python 2 tempfile.spooledtemporaryfile still of course returns python 2 cstringio.stringo , instead of python 3 io.bytesio required textiowrapper . i can think of these possible approaches: wrap python 2 cstringio.stringo python 3-style io.bytesio . i'm not sure how approach - need write such wrapper or 1 ex
Read more