[vtkusers] help for rendering a large amount of images

[Henry Blanco]

Hello David, thanks for your help and sorry for the late reply, I've
been absent for a couple of days.
Well we're newbies on vtk, ... therefore it would nice if you give us
more details on:
1- How to create a flat file from several images. I guess we have to use
some vtk classes, but we don't know which one.
2- How to achieve the mapping from the flat file memory address to the
vtkImageData.

Thanks in advance,

Henry 

On mar, 2015-11-03 at 11:03 -0700, David Gobbi wrote:
> Hi Henry,
> 
> 
> Please reply to the vtk list, not just to me.
> 
> 
> You're requirement of rendering "thousands of medical images" is
> way too vague.  Do you need to render them all simultaneously,
> i.e. will they all be on screen at the same time?  I really do not
> understand what you are trying to do.
> 
> 
> The vtkImageDataStreamer will be no help to you, because it always
> loads the entire volume.  It's job is to pull the data through the
> pipeline
> in small chunks, but the end result is still that the whole volume
> ends
> up in memory.
> 
> 
> Yes, vtkImageReslice can show a sagittal or coronal view by only
> streaming a small part of the volume into memory, but this will only
> work with certain reader classes.  For example, the vtkTIFFReader
> always reads entire slices, so it cannot read just one row of a
> slice that vtkImageReslice can then incorporate into a sagittal view.
> In fact, I think that only vtkImageReader2 can stream individual
> rows or columns of an image from disk.  The other readers can
> only stream the data slice-by-slice.
> 
> 
> You should seriously consider my recommendation of using memory
> mapping.  If you simply map a flat file to a memory address and then
> use that memory address as a pixel data inside a vtkImageData, then
> the operating system can make all the decisions about how and when
> to load the data from disk.
> 
> 
>  - David
> 
> 
> 
> On Tue, Nov 3, 2015 at 10:33 AM, Henry Blanco
> <henry.blanco at cbiomed.cu> wrote:
>         Thanks David for your soon reply. Ok, my problem is to load
>         and render thousands of medical images,
>         organized into series, by using VTK, but considering strong
>         limitations
>         in terms of RAM (e.g., only 128 or 256 MB of RAM available).
>         
>         To achieve this task, we have tried to use the
>         "vtkImageDataStreamer"
>         class, but we have failed. This class seems to load the whole
>         volume into
>         memory, therefore loading 2000 CT images (1GB) into memory may
>         fail if
>         we consider just 128 MB of RAM.
>         
>         We are thinking to partition the whole volume into K blocks
>         and to load
>         a block of images into memory just when it's needed. The
>         illusion of
>         having the whole volume loaded in memory could be achieved by
>         uploading/downloading one or more blocks of images to/from
>         memory when
>         needed. I'm wondering whether exist some vtk classes which can
>         be used
>         to picture a different view than the original (e.g., sagittal,
>         coronal,
>         or even oblique) without loading the whole volume of images.
>         
>         Henry
>         
>         On lun, 2015-11-02 at 17:29 -0700, David Gobbi wrote:
>         > What kind of views will you need?  Do you just have to view
>         the
>         > original
>         > slices?  If so, then the VTK pipeline's streaming will make
>         the job
>         > easy.
>         > If you need orthogonal or oblique views, things are more
>         difficult.
>         > Also,
>         > how is the data stored on disk?  If the whole volume is
>         stored on disk
>         > as a single flat file, then you can memory map the file.
>         >
>         >
>         >  - David
>         >
>         > On Mon, Nov 2, 2015 at 4:10 PM, Henry Blanco
>         <henry.blanco at cbiomed.cu>
>         > wrote:
>         >         Hello guys, I need some hints on how to render a
>         large amount
>         >         of images
>         >         (e.g., thousands of images) using just few RAM
>         resources
>         >         (e.g., 128 MB)
>         >         using the vtkImageReslice class for the whole
>         volume.
>         >
>         >         Thanks in advance
>         >
>         >         Henry
>         
>         
>         
>         
> 
>