[vtkusers] vtkImagePlaneWidget contrast control

[Jérôme]

Hi,
I think that the rmin/rmax value are directly related to the fine
ascii chart you
drawn, that is in fact the lookup table (Displayed_value in function
of pixel_value).
It means that:
rmin = L - W/2
rmax = L + W/2

HTH,
Jerome

2010/4/30 Jothy <jothybasu at gmail.com>:
> I think the rmin and rmax should be your scalar value minimum and maximum.
>
> Jothy
>
> On Fri, Apr 30, 2010 at 5:18 PM, somi <seesomi at gmail.com> wrote:
>> Hi Jothy,
>> On digging further, I found the right click was linked to
>> vtkImagePlaneWidget::WindowLevel
>>
>> Where window size and leve of the histogram were calculated and modified
>> based on mouse movements, to get rmin and rmax .
>> Finally , the lookuptable was modified LookupTable->SetTableRange( rmin,
>> rmax ); to adjust brightness/contrast.
>>
>> So, I am planning to do the following:
>>
>> from my vtkImagePLanewidget I would  GetLookupTable () and set its table
>> range rmin/rmax based on the Qt slider.
>> However I am not very clear between the relation of brightness/contrast
>> and   rmin/rmax in  LookupTable->SetTableRange( rmin, rmax );
>>
>> I think the window/level refer to the following in a histogram:
>>
>>              ____________
>>
>>             /
>>            /
>> __________/
>>          | ^ |
>>            L
>>          <-W->
>>
>> and they are related to brightness/contrast by the following:
>>
>>    minval = min(image)
>>    maxval = max(image)
>>    level = (1-brightness/100.)*(maxVal - minVal) + minVal
>>    window = (1-contrast/100.)*(maxVal - minVal)
>> where brightness/contrast can vary from 0 to 100.
>>
>> So what value should I use for rmin/rmax in LookupTable->SetTableRange(
>> rmin, rmax ); ?
>>
>> Regards,
>> Somi
>>
>> On Fri, Apr 30, 2010 at 11:29 AM, Jothy <jothybasu at gmail.com> wrote:
>>>
>>> I don't have exact answer for this. But , I think you need to
>>> manipulate the observers.HAve a look at this
>>>
>>> http://www.cmake.org/Wiki/VTK_Examples#User_Interaction
>>>
>>> Jothy
>>>
>>> On Fri, Apr 30, 2010 at 3:58 PM, somi <seesomi at gmail.com> wrote:
>>> > Hi Jothy,
>>> > I want the brightness/control through a user control slider (in Qt). I
>>> > also
>>> > show the surface overlaid over the image plane widget
>>> >
>>> >  Which function should I override to implement my own
>>> > brightness/contrast
>>> > control ? I didn't find anything specific @
>>> > http://www.vtk.org/doc/nightly/html/classvtkInteractorStyleImage.html
>>> >
>>> > Also while playing with the interactor, I noticed that if my mouse is
>>> > over
>>> > an image and I drag left/right I can adjust contrast and if I click and
>>> > drag
>>> > up/down I can adjust contrast.
>>> > Do I have to imement my own interactor style and override right click ?
>>> > Isn't there any SetContrast/SetBrightness interface ?
>>> >
>>> > Regards,
>>> > Somi
>>> >
>>> >
>>> >
>>> > On Fri, Apr 30, 2010 at 10:44 AM, Jothy <jothybasu at gmail.com> wrote:
>>> >>
>>> >> I think by  setting Interacto Style to InteractorStyleToImage
>>> >>
>>> >> Jothy
>>> >>
>>> >> On Fri, Apr 30, 2010 at 3:31 PM, somi <seesomi at gmail.com> wrote:
>>> >> > Hi,
>>> >> > I have a 3D volume (vtkImage) which I show through 3 orthogonal
>>> >> > vtkImagePlaneWidgets. How can I add brightness and contrast control
>>> >> > to
>>> >> > this
>>> >> > widget ?
>>> >> >
>>> >> > Regards, Somi
>>> >> >
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>>> >
>>> >
>>
>>
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