[vtkusers] Loading images from memory *not files*

[David Gobbi]

Hi Robert,

Your situation is fairly rare, very few users would ever read PNG
format from memory.  So this functionality has not yet been added to
VTK.

There is a class called vtkImageImport class for reading uncompressed
images into VTK, and it would be nice if someone could write a
vtkPNGImport and vtkJPEGImport for handling compressed data.

A possible quick-and-dirty fix is to write the data to a pipe and read
it back in through the vtkPNGReader.  That way it can be decompressed
without having to go back to disk.

   David


On Wed, Feb 24, 2010 at 6:35 AM, Robert Haines <rhaines at manchester.ac.uk> wrote:
>> PNG is a file format and PNGReader implements it. Nothing crazy here.
>
> No, PNG is a data format. A PNG file is simply a file with that data format in it. I have some PNG data in memory that I would like to decode and use rather than load it from a file. Given that when you load a PNG file you would load it into memory to decode it I was hoping that you could do that with PNGReader or similar, that's why I thought I was going crazy when I thought that the only way of loading PNG data into vtk was to have it in a file on disk.
>
> So my question was, can I do this with vtk?
>
>> You need to create a vtkImage and populate its data via write pointer.
>
> I can't see a vtkImage class (5.4.0) but if I was to use something like that (vtkImageData?) then it looks like I would have to do the PNG decode myself. Is that right? Even when vtk already links libpng and can do this if it's in a file?
>
> Cheers,
> Rob
>
>> Robert Haines wrote:
>>> Hi all,
>>>
>>> Subject says it all really. I have an image (a PNG in this case but I'd like to be general here really) in memory and I'd like to use it in the normal VTK way - as if it had been read in by vtkPNGReader, for example. Is this possible? I've looked at the code for vtkPNGReader and it looks like the only way to read a PNG is from a file, which seems crazy! Have I missed something? Is there another way to do what I want?
>>>
>>> Thank you,
>>> Rob
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
>