The Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.


Math Forum » Discussions » Software » comp.soft-sys.matlab

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: sub-pixel shifting of a matrix
Replies: 14   Last Post: Feb 7, 2013 12:23 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Shalin Mehta

Posts: 6
Registered: 9/17/09
Re: sub-pixel shifting of a matrix
Posted: Sep 17, 2009 5:33 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Just found a useful solution: Use interp2 with '*linear' option. Works factor of 2.5 faster than imtransform. Any other ideas?

best
shalin
"Shalin Mehta" <shalinDOTmehtaHATESSPAM@gmail.com> wrote in message <h8ss9r$jhf$1@fred.mathworks.com>...
> Hello world,
>
> I have data defined over a grid, e.g.
> [xx yy]=meshgrid(-1:0.1:1); %each pixel represents distance of 0.1
> data=xx.^2+yy.^2 ;
>
> I need to translate this data by sub-pixel distances which will inevitably involve interpolation. I can live with linear interpolation as the data is sampled quite finely. I am using imtransform to achieve this. The shifted-data need to be obtained only over the original grid. I want extrapolated locations to be zero.
>
> xshift=0.235; yshift=-0.95; %Since shift is finer than sampling, sub-pixel shifting is required.
> xdata=[1 wt];
> ydata=[1 ht];
> T=maketform('affine',[1 0 0; 0 1 0; xshift yshift 1]);
> shifteddata=imtransform(data,T,'bilinear','XData',xdata,'YData',ydata);
>
> Results are satisfactory but slow as this shifting happens in the inner-most loop.
> Can anyone suggest a method that involves direct indexing and hence would be faster? Any neat algorithm published in the literature for sub-pixel translation?
>
> best
> Shalin




Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.