[Insight-users] Volume overlay

[robert tamburo]

What's the value of your label? In your previous code, the output of the add
filter is set to unsigned char, so you may have typecasting issues as David
alluded to.

Your current code looks okay to me. Try writing bwImage to disk to determine
if there is an ITK or VTK issue.


On Thu, Feb 10, 2011 at 3:15 PM, Sara Rolfe <smrolfe at u.washington.edu>wrote:

> I'm attaching my code.  The rescale intensity filter worked great to get
> the image data in the right right range.  But I'm still having a problem
> when I try to add the regions which will be labeled with color.  I move the
> data into the intensity range 100-200, and then use the add image filter to
> add the labeled image on top, so that I can use a piecewise colormap in VTK
> to apply colors to these values.  I think the add images may be where the
> problem is.  What I would rather do is mask the image with the labels so
> that the pixels in the image were replaced with the label value for all
> non-zero labels.  Is there anything like this implemented, or would I need
> to go through pixel by pixel and change the values?  I've only seen binary
> mask filters.
>
> Thanks,
> Sara
>
>
>
>
> On Feb 10, 2011, at 10:56 AM, David Doria wrote:
>
> On Thu, Feb 10, 2011 at 1:38 PM, Sara Rolfe <smrolfe at u.washington.edu>wrote:
>
>> Hello,
>>
>> I'm attempting to overlay an image with color.  I've had trouble finding
>> documentation on this, either in ITK or VTK.  The way I'm going about it is
>> to scale the values of the image down and then use the add image filter to
>> add the labels on top.  I could then use VTK to create a corresponding
>> colormap.
>>
>> However, I'm getting stuck on something that should be very simple.  My
>> operations to combine the two images are failing.  I think the problem is
>> the SubtractConstantFromImageFilter.  I've checked the output and it
>> looks like the constant is not being subtracted.  The input to this filter
>> is an image with a value of 0 for the background and 255 for the object.
>>  I'd like to change these to 0 and 1.  The pixel type is unsigned char.  I
>> use the following:
>>
>> SubFilterType::Pointer subFilter = SubFilterType::New();
>>  InputPixelType subValue = 254;
>>  subFilter->SetConstant(subValue);
>> subFilter->SetInput( imageInverter->GetOutput() );
>>  subFilter->Update();
>>
>> But the output image is still 0 - 255.  Am I missing something simple?
>>
>> Also, is there a better way to accomplish this task, or any examples
>> showing something similar?
>>
>> Thanks,
>> Sara
>>
>> Can you provide a compilable code snippet? I'm also not sure what you mean
> by "overlay with color"?
>
> Something that jumps out is that if you subtract 254 from an unsigned char
> you will be assigning a negative value to an unsigned char which is
> undefined.
>
> If all you are trying to do is map (0-255) to (0-1) you could use
> itkRescaleIntensityImageFilter
>
> http://www.itk.org/Wiki/ITK/Examples/ImageProcessing/RescaleIntensityImageFilter
> <http://www.itk.org/Wiki/ITK/Examples/ImageProcessing/RescaleIntensityImageFilter>
> David
>
>
>
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