[Dcmlib] Signed Images

[Mathieu Malaterre]

As a side note it seems NVidia has already a notion of scalar range in 
the ARB_Imaging extension.

HTH
Mathieu

On Jun 14, 2005, at 12:24 PM, Aris Basic wrote:

> I guess you miss understood me. Applyig W/L transformation to the 
> pixel data for display.
> and yeah OpenGL gives me range 0..1 but for some reason the textures 
> with signed pixel values
> have very small range in my case and i guess its not becasue of gdcm 
> butbecasue fo me or how opengl read it but ill
> continue to hunt :)
>
> thx for your help
> Aris
>
> Mathieu Malaterre wrote:
>
>> you're the boss ! I don't think opengl is giving you access to the 
>> scalar range, I believe it always assume texture are [0,1]
>>
>> Anyway he fastest ever solution would still be reading the value from 
>> the DICOM tags, by any chance do you have those values in your images 
>> ?
>>
>> Mathieu
>>
>> On Jun 14, 2005, at 12:07 PM, Aris Basic wrote:
>>
>>> applying it to the image in fastes possible way :)
>>> and correspodning formula is why i went towards OpenGL (should 
>>> allowe me to use GPU to do it)
>>> dont get how VTK adn some other libraries do it very fast withouth 
>>> GPU :(
>>>
>>>
>>> Mathieu Malaterre wrote:
>>>
>>>> For the window/level is is pretty easy:
>>>>
>>>> double range[2];
>>>> my_function(range, image);
>>>> // range now contains the pixel value min and pixel value max.
>>>>
>>>> level = (range[1]+range[0] )/2
>>>> window = range[1]-range[0]
>>>>
>>>> In theory there is a window/level tag in DICOM but I don't trust 
>>>> them :P
>>>>
>>>> HTH
>>>> Mathieu
>>>>
>>>> On Jun 14, 2005, at 11:38 AM, Aris Basic wrote:
>>>>
>>>>> I have some of my images havnot tested it with gdcm provided 
>>>>> images will probably do it and compare with vtkgdcmViewer.
>>>>> IM trying to display them with OpenGL (creating and RECT texture 
>>>>> from pixel data [ opengl supposedly shoudl be able to
>>>>> deal with signed pixel data , but doesnt look like its doing )
>>>>> (i tryed too figgure out how is VTK donig the W/L transfomration 
>>>>> and rest but did not have luck finding that piece of code quickly 
>>>>> :)
>>>>>
>>>>>
>>>>> Jean-Pierre Roux wrote:
>>>>>
>>>>>> Aris Basic wrote:
>>>>>>
>>>>>>> is gdcm doing any conversion on pixel data from signed 
>>>>>>> (pixelrepresentation == 1) images ?
>>>>>>> pixelrepresentation == 0 images i can display nicely but 
>>>>>>> representation 1 they come up strange :(
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> gdcm doesn't make any transformation for 'signed pixels'.
>>>>>> It's up to the user to deal with the sign.
>>>>>> How do you display the image?
>>>>>> Did you try with vtkgdcmViever? (of course, you need VTK ...)
>>>>>>
>>>>>> In our test data set ( gdcmData), there are a few 'signed pixels' 
>>>>>> images :
>>>>>>
>>>>>> MR-MONO2-16-head.dcm CT-MONO2-16-chest.dcm
>>>>>> CT-MONO2-16-ankle.dcm  CT-MONO2-16-ort.dcm
>>>>>> CT-MONO2-16-brain.dcm
>>>>>> GE_RHAPSODE-16-MONO2-JPEG-Fragments.dcm 
>>>>>> GE_GENESIS-16-MONO2-Uncompressed-UnusualVR.dcm
>>>>>> GE_GENESIS-16-MONO2-WrongLengthItem.dcm 
>>>>>> PICKER-16-MONO2-No_DicomV3_Preamble.dcm
>>>>>> 012345.002.050.dcm
>>>>>>
>>>>>> Did you try to display them?
>>>>>> HTH.
>>>>>>
>>>>>> Jean-Pierre
>>>>>>
>>>>>>>
>>>>>>> jsut trying to find a bug :) not pointing fingers
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Thx for reporting it.
>>>>>> Could you send us one of your images, so we can check 'at home' 
>>>>>> if there is any problem.
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Aris
>>>>>>> _______________________________________________
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>>>>>>> Dcmlib at creatis.insa-lyon.fr
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>>>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>
>>>
>>
>