[Insight-users] Question on MHD format

[Karthik Krishnan]

The position tag lets you represent subregions.

Here's the header
...
...
Position = -10.5 -10.5 -10.5
...

That means the origin of this image is at -10.5. So if you had a small 
image that represented a subregion of a larger image, you could have the 
subregion handled by itk::Image at the right physical location in the 
image by specifying its origin at the appropriate position. We do this 
often during registration where images from different modalities might 
have different physical extents.

HTH
karthik

Luis Ibanez wrote:

>
> Hi Tim,
>
> An easier way of saving disk space is by compressing
> your images.
>
> The MetaImage formal let you gzip your raw files.
>
> What you will have to do is to edit the .mhd files
> and update the name of the .raw file in order to
> include the additional extension  .raw.gz (or any
> other name that you decide to give to the compressed
> file).
>
> This compression works quite well for labeled images
> since it is based on Run Length Encoding. It doesn't
> work quite well on noisy images though....
>
> Note that gzip compression is lossless, so you shouldn't
> have any concerns about degradation of the image data
> due to the compression.
>
> Please give it a try to compress the raw files (and
> modify their name accordingly in the .mhd files) and
> let us know if you find any problems.
>
>
>
>     Thanks
>
>
>
>        Luis
>
>
>
>
> =======================
> Tim Soper wrote:
>
>> Hi,
>>    I intersted in finding a way to reduce the space
>> taken up on my hard drive by a number of raw data
>> files roughly 512^3 in size. I find that I am making
>> several images that are both clipped versions of the
>> original large image as well as creating segmented
>> images of these original images for different
>> applications.
>>    I would like to keep these large images, but I am
>> wondering if there is a way to specify a desired
>> region of an image through some sort of MetaImage
>> header tag. For example, if I wanted just a clipped
>> portion of my original image, say 256^3 in size, can I
>> simply make a new header file that specifies that
>> sub-region of the original image, but referencing the
>> same large ElementDataFile? This would preclude
>> creation of multiple data files with redundant data.
>>    Also, It would be convenient if rather than
>> creating new images of segmented regions of my
>> original image, I could add another raw data file
>> reference to the header that contained an image mask
>> of the segmented regions rather than rewriting the
>> same image data again. I have looked through the MHD
>> file formats and there doesn't appear to be any tags
>> that suit this function.
>> Please let me know if this is possible.
>>
>> Tim
>>
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