[vtkusers] Texture Mapping Image Quality

[David Gobbi]

Hi Patrick,

You can try using vtkImageActor instead of vtkTexture and vtkActor,
I checked the c++ code and it doesn't resample the image regardless
of the size.

The vtkImageActor doesn't offer as much flexibility as vtkTexture,
but it will probably do what you need.

 - David

On Mon, 30 Aug 2004, Patrick Lowry wrote:

> David:
>
> VTK is subsampling the image.  Even for an image of less than 1000x1000
> pixels, it resamples to a power of two (as the documentation says).  For
> larger images it must resample it much more.
>
> Are we stuck with this or are there additional settings that allow bigger
> image sizes?  It seems that large memory capacity, both on the mother board
> and on the video card (128mb) would allow larger images.
>
> Thanks,
> Patrick
>
> At 02:10 PM 8/30/2004, you wrote:
> >Hi Patrick,
> >
> >VTK is subsampling the image before creating the texture, probably because
> >VTK thinks it is too large for your graphics card.
> >
> >Try using
> >atext DebugOn
> >
> >and see what kind of info it gives you.  You might have to break the
> >image into patches in order to render it at full resolution.
> >
> >  - David
> >
> >
> >On Mon, 30 Aug 2004, Patrick Lowry wrote:
> >
> > > David:
> > >
> > > The TIFF is 8-Bit Paletted.  A comparitive image is shown below.  The TIFF
> > > being loaded is on the left and a capture of the rendered texture map is on
> > > the right.  The script has the 32-bit flag setting you suggested.   It is a
> > > satellite image showing roads etc.
> > >
> > > Thanks for your help.
> > >
> > > Cheers,
> > > Patrick Lowry
> > >
> > > Comp.jpg
> > >
> > >
> > > At 01:17 PM 8/30/2004, you wrote:
> > > >Hi Patrick,
> > > >
> > > >What do you mean by "image characteristics"?  I'm guessing that your
> > > >image is either 8-bit greyscale or 24-bit RGB if it is a TIFF.  If
> > > >this is the case, then VTK will use the data as a texture without
> > > >any conversion, and the only things that should impact quality are
> > > >the 32-bit flag I mentioned, and the actor's lighting properties.
> > > >
> > > >By "low quality" do you mean the image looks noisy, or do you mean
> > > >that the contrast is poor?
> > > >
> > > >On Mon, 30 Aug 2004, Patrick Lowry wrote:
> > > >
> > > > > Hi David:
> > > > >
> > > > > Thanks for the quick reply.
> > > > >
> > > > > I tried your recommended setting and it didn't change the quality.
> > > > >
> > > > > Do image characteristics affect how they render?
> > > > >
> > > > > Patrick
> > > > >
> > > > > At 08:36 AM 8/30/2004, you wrote:
> > > > > >Hi Patrick,
> > > > > >
> > > > > >Some graphics cards default to 16-bit textures, be sure to force
> > > > > >VTK to use 32-bit textures:
> > > > > >
> > > > > >atext SetQualityTo32Bit
> > > > > >
> > > > > >  - David
> > > > > >
> > > > > >
> > > > > >On Mon, 30 Aug 2004, Patrick Lowry wrote:
> > > > > >
> > > > > > > To All:
> > > > > > >
> > > > > > > The texture mapping capabilities of VTK are amazing but I
> > noticed image
> > > > > > > quality loss from the original TIFF.  Texture mapping done by a
> > > > commercial
> > > > > > > program I have does not suffer the same quality loss.  The essence
> > > > of the
> > > > > > > image part of the TCL script are shown below.  Any ideas on
> > preventing
> > > > > > > image quality loss?
> > > > > > >
> > > > > > > Thanks in advance.
> > > > > > >
> > > > > > > Patrick Lowry
> > > > > > >
> > > > > > > .
> > > > > > > .
> > > > > > > .
> > > > > > > vtkTIFFReader readTIFF
> > > > > > >    readTIFF SetFileName "data/test1comp.TIF"
> > > > > > >    readTIFF Update
> > > > > > > vtkTexture atext
> > > > > > >    atext SetInput [readTIFF GetOutput]
> > > > > > >    atext InterpolateOn
> > > > > > > .
> > > > > > > .
> > > > > > > .
> > > > > > > vtkTextureMapToPlane test
> > > > > > >    test SetInput [normals GetOutput]
> > > > > > >    test SetOrigin $xmin $ymin 0.0
> > > > > > >    test SetPoint1 $xmax $ymin 0.0
> > > > > > >    test SetPoint2 $xmin $ymax 0.0
> > > > > > >
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