[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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