[gdal-dev] problem with ArcSDE raster (negative values)

[Kor de Jong]

Hi Bart,

On Tuesday 08 December 2009 10:45:25 bartvde at osgis.nl wrote:
> I've debugged the problem to the following part of
> frmts/sde/sderasterband.cpp:
>
>     if (bits_per_pixel >= 8) {
>         memcpy(pImage, pixels, block_size);
>         GByte *p = reinterpret_cast<GByte*>(pImage);
>     } else {
>
> The values in the pixels variable are still okay, and contain mostly
> negative values as well as 0 (for example -42).
>
> The p variable only contains positive values and 0 values.

What differences do you see when reading the data using ArcMap and
reading it using gdal?
- Is it only the no-data values that get truncated?
- Do all negative values get converted to a positive value?
- Something else?

The piece of code you're showing only deals with copying bits and bytes
from one buffer to another. These buffers have types that are convenient
for doing that and have no relation with the real type of the values in
the buffers. Using these pointers to test the values is not very useful,
I think. Why do you think this piece of code must contain a bug?

BTW, the current trunk version of this module looks different. Maybe
upgrading gdal solves your problem already?

Sorry, more questions than answers...

Kor