java - Scale 2D-Array using Bicubic Interpolation -

-

i want scale arbitrary double[][] double[][] different dimensions. values of resulting array should calculated based on input array using bicubic interpolation.

i know done in image processing decades now, unable find library or @ least working code snippet works 2d-array rather specific image objects, that's why i'm asking here.

more specific requirements:

as far i've understood, value of point between corners of 3x3-grid can calculated directly using bicubic interpolation, first function need 

double interpolate(double[][] grid3by3, double x, double y)`

where x , y between 0.0 , 1.0

the next step of course ease process 3x3 grid chosen every point automatically , can like

`double[][] interpolate(double[][] input, int newwidth, int newheight)`

this me new array specified dimensions same borders input array.

where want this:

`double[][] interpolate(double[][] input, int newwidth, int newheight,                         double minx, double miny, double maxx, double maxy)`

the min , max values define bounding box can subset of initial array not need start or end @ exact index value of input array (e.g. corner can @ (5,3) or (5.25, 3.7), can't cut off input array @ index value). bounding box become extent of new array , values interpolated input array.

oh, , fyi: digital elevation models, please tell me if approach totally wrong in first place ;)

just wanted share how solved problem (or rather, didn't):

for while, tried own bicubic interpolation algorithms started (get inspiration here), , @ point, looked work, , if want decent approximation work numbers, it's fine.

but: if scale image fancy new algorithm, see how crappy results are. unless math behind , know you're doing (and don't, because that's why read this), don't try , code yourself.

and here's workaround: imagej , this:

// works same for: byte, short, int float[] mydata;      // create new image. change 32 16 short or 8 byte imagestack stack = imagestack.create(width, height, 1, 32); stack.setpixels(mydata, 1); imageprocessor processor = new imageplus("", stack).getprocessor(); // crop , scale processor.setroi(x, y, rwidth, rheight); imageprocessor result = processor.crop().resize(newwidth, newheight); // retrieve results float[] myscaleddata = (float[]) result.getpixels();

i know, it's not it's intended for, , unfortunately, there no functions 64 bit datatypes, results of high quality , imagej not of weight carry around... still, copy , paste relevant code parts, imagej in public domain.


Comments

Post a Comment

Popular posts from this blog

c++ - Function signature as a function template parameter -

-
i'd use function signature template argument. works great classes, when try same trick function templates, msvc throws error: error c2768: 'func' : illegal use of explicit template arguments here's code: template <typename signature> void func(); template <typename r, typename a1> void func<r(a1)>(); what should make work? you cannot partially specialize function template, not supported language. can create partially specialized class template static member function, , possibly trampoline function instantiate class template , invoke static function. something this: namespace detail { template<typename signature> struct helper; template<typename r, typename a1> struct helper<r(a1)> { static void call() { // stuff r , a1... } }; } template<typename signature> void func() { detail::helper<signature>::call(); }
Read more

algorithm - What are some ways to combine a number of (potentially incompatible) sorted sub-sets of a total set into a (partial) ordering of the total set? -

-
i have sorting problem i'm pretty sure doesn't have canonical "answer" - has number of different approaches, each pros/cons. i'm interested in hearing different approaches. suppose bunch of people {p_i | i=1,...,m} ranking favorite ice cream flavors. in total there n different flavors, single person p_i ranks n_i << n flavors or familiar with. i'm interested in combining these sub-rankings plausible overall ranking of n flavors. for concrete situation: m , n both 1000 (by coincidence), , each n_i 20 . can assume there's enough overlap in flavors people rank such no flavor "isolated". again, i'm interested in hearing different ways approach this, if there isn't single clear answer. thanks! one way approach problem construct directed cyclic graph representing of constraints on ordering of elements. nodes in graph represent different elements compared , have edge first node second node if had ranked first e...
Read more

How to call a javascript function after the page loads with a chrome extension? -

-
there's function on page want call after loads. not own page, can't insert html it. can please provide specific examples how chrome extension or greasemonkey? (function submitaction() ). both chrome extensions , greasemonkey offer ways specify when script inject if executed. in chrome extension, you set in manifest : "content_scripts": [ { "run_at" : "document_idle", in greasemonkey compatible userscripts, set in metadata // @run-at document-end in both cases, have add script if want ensure resources loaded when function executed : document.addeventlistener('load', submitaction);
Read more