Re: [Vxl-users] confused how to get and manipulate the different planes of an image

[Amitha P. <ami...@us...>]

On 02/04/2011 04:30 PM, Michael Repucci wrote:
> But now I need to know what the different planes are, so I can know
> which ones to use when I need to display the image or combine
> information across planes.
[...]

vxl does not have a way to attach semantic labels to the plane indices.


> If not, then let's assume I can get that information from somewhere
> else. Question (2): how can I create a view from nativeView that looks
> at only the (e.g.) second plane.
[...]

To get an image of a single plane:
   vil_image_view<X> pl = vil_plane( im, plane_index );
Note that pl will share memory with image, and the pixels of pl may not 
be contiguous. Certainly will not be contiguous if im stores the 
planes/channels in an interleaved fashion. (I.e., RGBRGB instead of RRGGBB.)


> And question (3), if I'd like to reorder the representation in memory of
> (a possible subset of) the planes, say from BGRA to RGB, what do I have
> to do so that (e.g.) myRgbView.top_left_ptr() will point to contiguous
> memory?
[...]

To get a contiguous memory subset of the planes, you will have to deep 
copy. You can use vil_plane to make your life easier:

   vil_image_view<X> tgt(ni,nj,np,1); // for interleaved store
   // vil_image_view<X> tgt(ni,nj,1,np ); // for planar store

   for i = 1 to num planes to copy {
     vil_plane(tgt,i).deep_copy( vil_plane( src, map[i] ) );
   }


None of the snippets above have been compiler tested, let alone run, but 
it should get you started.

Hope this helps.

Amitha.