[Dcmlib] PixelPaddingValue

[Aris Basic]

Dono i just think it would be probably easier for gdcm lib to do the 
chanegs like pixelpadding and conversion from signed to unsigned pixel 
data this is what i ment with std (Notes):

C.7.5.1.1.2 Pixel Padding Value
Pixel Padding Value (0028,0120) is used to pad non-rectangular images to 
rectangular format.
The native format of some images is not rectangular. It is common for 
devices with this format to
pad the images to the rectangular format required by the DICOM Standard 
with a specific pixel
value that is not contained in the native image. This attribute 
specifies the value of this padding
value.
Notes: 1. When the relationship between pixel value and X-Ray Intensity 
is unknown, it is
recommended that the following values be used to pad with black:
0 if Photometric Interpretation (0028,0004) is MONOCHROME2.
2BitsStored - 1 if Photometric Interpretation (0028,0004) is MONOCHROME1.
2. When the relationship between pixel value and X-Ray Intensity is 
known (for example as
defined by Pixel Intensity Relationship (0028,1040) and Pixel Intensity 
relationship Sign
(0028,1041)), it is recommended that a value equivalent to air be used.

btw when newer gdcm give out message that pixeldata has to bin downshift 
what actualy happens ?
(was looking at gdcm code but i all i've seen is the printing of the 
Warn message).
(i noticed that with JPEG Lossless compresed 12bit images (packed in 16) 
i personaly have to multiply each pixel value with 256 (16*16)
and for LEI images its enoigh to multiply it by 16 (in order to adjust 
its 12bit range value in 16bit space)
(at least that gives me results (on display) comparable to other dicom 
viewer [efilm,...] ))

Aris


Jean-Pierre Roux wrote:

> Aris Basic wrote:
>
>> Just a question shouldnt  gdcm replace PixelPadding value with the 
>> either black or something else (according do DICOM std) ?
>
>
> Hi, Aris.
> What do you mean by "according do DICOM std"?
>
> The PPV (0028,0120) is used mostly to fill in the corners of round 
> images , just to tell the user no to loose time making computations on 
> those meaningless pixels . Any pixels in the image that have this 
> value are not to be treated as meaningful objects - but as background 
> color.
>
> It's up to the user to deal with this information, don't you think so?
>
> Well ...
> Probabely 'vtkgdcmViewer' doesn't deal with it, that can be a problem 
> if the PPV is a  very high value (image will be displayed very dark, 
> the first time)
> But vtkgdcmViewer is just a little (*very* usefull, but little) tool , 
> side of gdcm.
>
> Jean-Pierre
>
>>
>> Aris
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