Comments on: Resetting my expectations: What do users know about new product features?

By: Steve

Steve — Fri, 31 Mar 2006 13:09:16 +0000

Jani – I assume you are asking how to multiply an integer array by some floating-point scalar. In MATLAB 7, this works fine; you don’t need to convert to double first. In earlier versions, use the Image Processing Toolbox function immultiply.

By: jani

jani — Thu, 30 Mar 2006 06:43:04 +0000

please tell me how to do multiplication in image processing without using im2double conversion ?

By: Steve

Steve — Mon, 06 Mar 2006 13:33:26 +0000

Greg – imtransform can handle many types of spatial transformations. However, it’s meant for transforming from one Cartesian grid to another. If you have image samples in polar coordinates and want to create an image on a Cartesian grid, I suggest you look at griddata.

If these first few blogs are successful, then I predict there will be more.

By: Greg

Greg — Fri, 24 Feb 2006 08:53:45 +0000

Hi Steve,
I’m another of those who didn’t follow the tform introduction. However, I’m casting around in the documentation now because I’d like to do polar and back to cartesian transformations of images. Is there something that will do non-affine transforms? Any pointers? Google is letting me down…

Cheers,
greg

PS more blogs from TMW would be great.

By: Richard

Richard — Tue, 21 Feb 2006 22:43:52 +0000

Hi Steve

I am one of those people who wasn’t aware of the tform functionality, despite having used the image processing toolbox for the last year and a half for some of my PhD work.

I suppose it’s because most of the time the transformations I work with are at worst projective, so I only ever need to use constant matrices (and their inverses). Because I tend to work with points extracted from images, rather than images themselves, points are easily transformed by simple matrix multiplication. However, from reading the documentation, imtransform looks like a very useful function!