[vtkusers] Bug in vtkTIFFReader reading multi-paged tiff file
David Gobbi
david.gobbi at gmail.com
Fri Jan 17 14:50:04 EST 2014
Are you doing anything that would interfere with the alpha blending,
like using depth peeling?
On Fri, Jan 17, 2014 at 12:26 PM, Maarten Beek <beekmaarten at yahoo.com> wrote:
> Setting the opacity in the callback would enable me to check the order in
> which they were added to the renderer:
>
> if( m_pWidget->m_pDrrActor && m_pWidget->m_pTIFFActor )
> {
> vtkPropCollection* props =
> m_pWidget->m_pRenderer->GetViewProps();
> props->InitTraversal();
> vtkProp* prop = NULL;
> while( prop = props->GetNextProp() )
> {
> if( prop ==
> vtkProp::SafeDownCast(m_pWidget->m_pDrrActor) )
> {
> m_pWidget->m_pDrrActor->SetOpacity(1.0);
> m_pWidget->m_pTIFFActor->SetOpacity(0.5);
> break;
> }
> if( prop ==
> vtkProp::SafeDownCast(m_pWidget->m_pTIFFActor) )
> {
> m_pWidget->m_pTIFFActor->SetOpacity(1.0);
> m_pWidget->m_pDrrActor->SetOpacity(0.5);
> break;
> }
> }
> }
>
> Didn't solve to problem though....
>
> I have made an algorithm that adds an alpha value to the tiff image:
>
> vtkImageIterator<T> inIt(inData, outExt);
> vtkImageIterator<float> outIt(outData, outExt);
> int numIn = inData->GetNumberOfScalarComponents();
> float alpha = self->GetAlpha();
>
> // Loop through ouput pixels
> while( !outIt.IsAtEnd() )
> {
> T* inSI = inIt.BeginSpan();
> float* outSI = outIt.BeginSpan();
> float* outSIEnd = outIt.EndSpan();
> while( outSI < outSIEnd )
> {
> // now process the components
> for( int i = 0; i < numIn; ++i )
> {
> *outSI = static_cast<float>(*inSI);
> ++outSI;
> ++inSI;
> }
> *outSI = alpha;
> ++outSI;
> }
> inIt.NextSpan();
> outIt.NextSpan();
> }
>
> in order to go through vtkImageActor::HasTranslucentPolygonalGeometry()
> successfully.
>
> Didn't solve it either.
>
> I checked an older app of me in which I overlayed a transparent binary image
> on top of its original image. This worked fine using vtkActors. But in the
> example both images had the same extent and the order of the actors was
> predetermined.
>
> Maarten
>
>
> On Thursday, January 16, 2014 5:30:47 PM, David Gobbi
> <david.gobbi at gmail.com> wrote:
> On Thu, Jan 16, 2014 at 3:13 PM, Maarten Beek <beekmaarten at yahoo.com> wrote:
>> I think I want to blend 50/50, so I could set the opacity accordingly in a
>> callback initiated by a StartRender event?
>
> You can set the opacity anywhere. You just have to make sure that the
> opacity
> is set correctly, and you have to make sure that the images are in the
> correct order. The thing about the images being in the correct order
> is non-negotiable. You have to do it. Playing with depth isn't going
> to help. The images actually have to be rendered in the right order
> (an opaque image first, and a 50% opacity image after).
>
>> I have played around with vtkImageStack; I seemed to get only the first
>> (or
>> last) image of the stack or (with transparency) all images blended
>> together... I want one image of the stack blended with another (2d) image.
>> Secondly, I thought creating 100 actors and adding them to a stack was
>> quite
>> slow.
>
> Were you setting layer numbers (in the vtkImageProperty) for the images that
> you added to the stack? Were you setting VisibilityOff for the images that
> you
> didn't want to show, and setting the correct Opacity for the images that you
> wanted to blend?
>
> David
>
>
>
>
>> On Thursday, January 16, 2014 4:58:53 PM, David Gobbi
>> <david.gobbi at gmail.com> wrote:
>> On Thu, Jan 16, 2014 at 2:45 PM, Maarten Beek <beekmaarten at yahoo.com>
>> wrote:
>>> vtkImageActor::HasTranslucentPolygonalGeometry() seems to want image data
>>> of
>>> type unsigned char and 2 or 4 components in order to do transparency. I'm
>>> using vtkImageShiftScale to get unsigned char and am working on an
>>> algorithm
>>> to add an alpha component to my one component tiff data. Curious if this
>>> does the trick.
>>
>> I strongly suggest that you use vtkImageSliceMapper and vtkImageSlice
>> to display your images instead of using vtkImageActor.
>>
>>> I can understand the order is important if one of the actor is opaque,
>>> but
>>> why would this still be important when both are 50% transparent.
>>
>> That's not how alpha-blending works. If both images are 50%, then the
>> frontmost image is displayed at 50%, and the second image gets 25%,
>> and the background gets the remaining 25%. That's how translucency
>> works, both in real-life and in computer graphics.
>>
>> If you want to blend images 50/50, then the frontmost image should have
>> 50% opacity and the backmost image should have 100% opacity.
>>
>>> In my app the loading of each image is initiated through a button. I
>>> would
>>> like to create an app which is independent of the order in which the user
>>> clicks these buttons.
>>
>> Order is crucial. That's why I recommend that you use vtkImageStack.
>> It makes it possible to explicitly set the layer number for each image.
>>
>> - David
>>
>>
>>
>>> On Thursday, January 16, 2014 3:25:11 PM, David Gobbi
>>> <david.gobbi at gmail.com> wrote:
>>> Are you using vtk-master (or perhaps a vtk 6.1 release candidate)?
>>> The TIFF reader had a serious multi-frame bug in older versions.
>>>
>>> First, note that the vtkTIFFReader doesn't just give you the raw data
>>> from the files, it seems to pass it through a lookup table sometimes.
>>> And I'm not sure exactly how it deals with alpha, and to be honest,
>>> I wouldn't trust it.
>>>
>>> I'm really not sure what you mean when you say "The order of adding
>>> the actors to the renderer matters, but I try to avoid this by using
>>> transparency." The order in which you add images is _crucial_ when
>>> you are using transparency.
>>>
>>> Are you using the vtkImageStack? It's a class that is designed
>>> specifically to handle layered rendering of images.
>>>
>>> David
>>>
>>>
>>>
>>> On Thu, Jan 16, 2014 at 12:40 PM, Maarten Beek <beekmaarten at yahoo.com>
>>> wrote:
>>>> Hi David,
>>>>
>>>> Is it possible to show all images in a multi-paged tiff transparently?
>>>>
>>>> Only when I show the 1st image (page), I see a 2nd 2d image (both are
>>>> transparent).
>>>> As soon as I move to another tiff image (page), the 2d image disappears.
>>>> It
>>>> returns when I move back to the 1st tiff page.
>>>>
>>>> The multi-paged tiff is one component, and I am thinking of an algorithm
>>>> to
>>>> add an alpha component, but can hardly believe this would be required...
>>>>
>>>> The order of adding the actors to the renderer matters, but I try to
>>>> avoid
>>>> this by using transparency.
>>>>
>>>> Moving one image in front of the other by changing its z-coordinate
>>>> using
>>>> vtkImageActor::SetPosition() doesn't help.
>>>>
>>>> Maarten
>>>>
>>>>
>>>>
>>>> On Friday, November 8, 2013 4:36:06 PM, Maarten Beek
>>>> <beekmaarten at yahoo.com>
>>>> wrote:
>>>> Hi David,
>>>>
>>>> Using VTK 6.0.0, sorry ;-)
>>>>
>>>> Should I send you the tiff file so you can play with it?
>>>>
>>>> Now I seem to have your attention:
>>>>
>>>> - How do I display a multi-page tif? I don't seem to see the different
>>>> images using a vtkImageSlice.
>>>>
>>>> - What would be good values for the window and level parameters? I am
>>>> using
>>>> window = range[1]-range[0] and level = 0.5*(range[0]+range[1]) which
>>>> works
>>>> ok for this multi-page tif, but gets me nowhere when I try to display a
>>>> drr.
>>>>
>>>> Thanks - Maarten
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Friday, November 8, 2013 4:23:23 PM, David Gobbi
>>>> <david.gobbi at gmail.com>
>>>> wrote:
>>>> Hi Maarten,
>>>>
>>>> Which version of VTK are you using? I believe that this bug has been
>>>> fixed in the master branch by a commits in the following topic merge:
>>>> http://vtk.org/gitweb?p=VTK.git;a=commitdiff;h=7e3d5270
>>>>
>>>> It was not fixed in time for VTK 5.10, however.
>>>>
>>>> David
>>>>
>>>>
>>>> On Fri, Nov 8, 2013 at 2:12 PM, Maarten Beek <beekmaarten at yahoo.com>
>>>> wrote:
>>>>> Hi all,
>>>>>
>>>>> vtkTIFFReader crashed for me while loading a multi-paged tiff file.
>>>>>
>>>>> The crash occured in vtkTIFFReader::ReadGenericImage(), because
>>>>> this->OutputExtent was not set (still NULL).
>>>>> The scalar type for the image I was loading was unsigned short, so it
>>>>> happened at line 1368.
>>>>>
>>>>> I changed void vtkTIFFReader::ReadVolume(void* buffer) into void
>>>>> vtkTIFFReader::ReadVolume(void* buffer, int outExt[6]) and added the
>>>>> line
>>>>> this->outputExtent = outExt.
>>>>>
>>>>> This solved my crash.
>>>>> I am not sure I am on to something, but thought to let you know.
>>>>>
>>>>> Maarten
>>>
>>>
>>
>>
>
>
More information about the vtkusers
mailing list