[osg-users] Image Resolution in VPB

Martins Innus minnus at ccr.buffalo.edu
Mon Mar 23 09:18:26 PDT 2009


Robert,

	OK, no problem, thanks.  It's pixelated just because i zoomed in to the 
image to highlight the effect i was seeing.

Martins


Robert Osfield wrote:
> Hi Matins,
> 
> Slight variations of the pixel colour may come about due to GDAL 
> interpolating data, interpolation done with VPB, or the edge boundary 
> equalization.  The small variation you are seeing might simply be down 
> to this, it's not something at this stage I'd even flag up as a 
> problem.  It certainly doesn't looked to be the corner equalization bug, 
> as this just effects the corners.
> 
> BTW, the way is there a reason for the image being pixelated?  VPB 
> typically generates databases that use linear texture filtering.
> 
> Robert.
> 
> 2009/3/19 Martins Innus <minnus at ccr.buffalo.edu 
> <mailto:minnus at ccr.buffalo.edu>>
> 
>     Robert,
>            Thanks. Using -e with appropriate options did exactly what I
>     wanted, except for a slight error on the edges of the created
>     images.  If i overlay the created image tiles from the highest
>     resolution level on top of the original source imagery, they are
>     pixel to pixel exact except for a 1 pixel strip all the way around
>     the image.
>            It appears that the edge values are an average of what the
>     pixel value actually should be and the pixel directly adjacent to it
>     but what should be the next tile.
>            If you layer the attached good and bad images on top of each
>     other in an image viewer and toggle back and forth you can see the
>     pixels changing.
>            The good image is just the original source imagery zoomed in.
>      The bad image shows the vpb generated tile overlayed  on the left side.
> 
>            I saw the "corner equalization bug" posts, but this seems
>     like a different issue.
> 
>     This is under Redhat Enterpise Linux, x86_64, with OSG 2.8 and VPB
>     svn of a couple days ago.
> 
>     Martins
> 
> 
>     Robert Osfield wrote:
> 
>         Hi Martins,
> 
>         You could try to use the -e option.  It takes lat/longs as
>         input.  I don't know if it'll pad though, as I suspect it won't
>         unless the at least some of the input data covers the region.  
>         If you want to force the resolution to be the same then just use
>         the image and height res option.  I can't recall what they off
>         the top of my head, run osgdem --help to list them all.
> 
>         Robert.
> 
>         On Mon, Mar 16, 2009 at 6:12 PM, Martins Innus
>         <minnus at ccr.buffalo.edu <mailto:minnus at ccr.buffalo.edu>
>         <mailto:minnus at ccr.buffalo.edu <mailto:minnus at ccr.buffalo.edu>>>
>         wrote:
> 
>            Hello,
>                   I'm using VPB to generate a terrain database with 2ft
>            resolution elevation data and 1 ft resolution imagery. What I'm
>            trying to do is make the imagery in the highest resolution tiles
>            have the exact same resolution as the source imagery and also
>         still
>            be a power of 2 for the image tiles.
>                   I've verified that if I take a small input area where the
>            source imagery dimensions are a power of 2, I get what i want for
>            the final model.
>                   It seems that if I could tell VPB to "pad out" the
>         extents of
>            my input data to a power of 2 that should work as well.  I don't
>            care if its black or garbage or whatever.
> 
>                   Would the "-e" option do what I want if I specify extents
>            larger than the input data?  I'm about to give that a try but it
>            takes about three days for this job to run to completion, so I
>            figured I would ask if anyone has tried to do the same thing.
> 
>            Thanks for any insight.
> 
>            Martins
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