[vtkusers] bit wise operations for vtkImageData

[Jonathan Morra]

Your understanding is correct, however I cannot
use GetScalarComponentAsDouble and SetScalarComponentAsDouble because they
are way too slow in Java.  Do you have any other suggestions for how to do
this or will I have to write it myself in C++?

On Fri, Mar 25, 2011 at 12:29 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Jonathan,
>
> If I understand correctly, you have several binary images with exactly
> the same dimensions.  And you want to collapse them into a single
> image, by storing a bitfield in the pixels of that image.  So:
>
> To set bit "i" in pixel "xyz" (C++ code):
> int a = int(image.GetScalarComponentAsDouble(x, y, z, 0));
> a |= (1 << i);
> image.SetScalarComponentAsDouble(x, y, z, a);
>
> To clear bit "i" in pixel "xyz":
> int a = int(image.GetScalarComponentAsDouble(x, y, z, 0));
> a &= ~(1 << i);
> image.SetScalarComponentAsDouble(x, y, z, a);
>
> To test bit "i" in pixel "xyz":
> int a = int(image.GetScalarComponentAsDouble(x, y, z, 0));
> return ((a >> i) & 1);
>
> But I'm not sure if this is what you are trying to do.  I didn't fully
> understand your pseudocode.
>
>  - David
>
>
>
> On Fri, Mar 25, 2011 at 1:08 PM, Jonathan Morra <jonmorra at gmail.com>
> wrote:
> > I'm in Java and storing a large number of binary vtkImageData's.  I know
> > this is inefficient, and am searching for a better way to store them.
>  Right
> > now I have a hash of the vtkImageData's and a get/put function.
>  Basically I
> > want to mimic this get/put but with better storage.  I was thinking one
> way
> > to do this is to use bitwise logical operations to store the information
> in
> > the binary masks.  For instance, if we have 2 binary images, then we
> could
> > store that information in 1 vtkImageData using the following pseudo code.
> > private static final int IMAGE1_BIT_CHANNEL = 0;
> > private static final int IMAGE2_BIT_CHANNEL = 1;
> > private vtkImageData storedImage;
> > vtkImageData get(String image)  {
> >     int channel = image eq "image1" ? IMAGE1_BIT_CHANNEL :
> > IMAGE2_BIT_CHANNEL;
> >     vtkImageData return = new vtkImageData();
> >     foreach (pixel in storedImage)
> >         if (pixel at bit channel)
> >             return[pixel] = 1;
> >         else
> >             return[pixel] = 0;
> >     return return;
> > }
> > void put(String image, vtkImageData binaryImage) {
> >     int channel = image eq "image1" ? IMAGE1_BIT_CHANNEL :
> > IMAGE2_BIT_CHANNEL;
> >     foreach (pixel in binaryImage)
> >         if (pixel)
> >             storedImage at bit in channel = 1;
> >         else
> >             storedImage at bit in channel = 0;
> > }
> > This could be extended easily for 8 channels for a char image for
> instance.
> >  This operation would have to be very fast though cause it is done often
> on
> > the UI thread.
> > 1.  Is there a way to do this in VTK with Java?
> > 2.  Is this the best scheme for accomplishing my goal?
> > 3.  Is there a better scheme for doing this?
> > Thanks.
> > _______________________________________________
> > 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
> >
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20110325/6115e080/attachment.htm>