[Gdal-dev] Problem transforming PNG, BMP, JPEG datasets using GDALWarp API

Tue Apr 20 10:38:35 EDT 2004

Frank, 

Never mind, I found the problem. The reason it failed to work for the
datasets with world files was because I was opening these datasets read
only. While setting up the transformation I was trying to set the
projection of a read-only dataset because the projection was not set.
Then later when I was calling GDALCreateGenImgProjTransformer with the
GDALGetProjectionRef from the readonly dataset, it was getting an empty
string because the SetProjection failed and I didn't catch it because
I'm a bad boy and wasn't looking at the return type of SetProjection.

Sorry for the diversion.

Thanks,

Brian

-----Original Message-----
From: gdal-dev-admin at remotesensing.org
[mailto:gdal-dev-admin at remotesensing.org] On Behalf Of Brian Marchand
Sent: Tuesday, April 20, 2004 10:19 AM
To: gdal-dev at remotesensing.org
Subject: RE: [Gdal-dev] Problem transforming PNG, BMP, JPEG datasets
using GDALWarp API

One more item, I'm using the logic as outlined in the Warp tutorial.

-----Original Message-----
From: gdal-dev-admin at remotesensing.org
[mailto:gdal-dev-admin at remotesensing.org] On Behalf Of Brian Marchand
Sent: Tuesday, April 20, 2004 8:52 AM
To: gdal-dev at remotesensing.org
Subject: RE: [Gdal-dev] Problem transforming PNG, BMP, JPEG datasets
using GDALWarp API

Frank,

Sorry, I failed to mention that the new "warped" data sets were created
with the TIFF driver. Originally I was trying to stick with the driver
of the original dataset but came up against the "create" restriction for
these datasets. 

It seems as if the failure occurs when I transform from a UTM to GCS. It
works if I just change the datum. The WKT is below. I also took your
suggestion and tried it with the gdalwarp utility using the below WKT in
prf files and it worked! So now I need to see what the utility is doing
that I'm not.  

I'm guessing this has nothing to do with the PNG, BMP, or JPEG drivers
but more to do with the fact that these formats come with world files.

Thanks,

Brian

Source SRS:

PROJCS["UTM Zone
17",GEOGCS["NAD83",DATUM["North_American_Datum_1983",SPHEROID["GRS
1980",6378137,298.257222101,AUTHORITY["EPSG","7019"]],TOWGS84[0,0,0,0,0,
0,0],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","89
01"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AXIS["L
at",NORTH],AXIS["Long",EAST],AUTHORITY["EPSG","4269"]],PROJECTION["Trans
verse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_me
ridian",-81],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",
500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

Target SRS:

GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS
84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,
0],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901
"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AXIS["Lat
",NORTH],AXIS["Long",EAST],AUTHORITY["EPSG","4326"]] 

-----Original Message-----
From: gdal-dev-admin at remotesensing.org
[mailto:gdal-dev-admin at remotesensing.org] On Behalf Of Frank Warmerdam
Sent: Monday, April 19, 2004 3:38 PM
To: gdal-dev at remotesensing.org
Subject: Re: [Gdal-dev] Problem transforming PNG, BMP, JPEG datasets
using GDALWarp API

Brian Marchand wrote:
> Hello,
> 
> I've come across a problem where PNG, BMP, and JPEG datasets are
zeroed 
> out during a GDALWarp transform. I'm not sure if other formats do
this, 
> but I've seen this happen on these types. I have no problem with TIFF 
> files so as a temporary work around for these types; I copy them to 
> geotiff datasets before the transform. I'd prefer not to do this, so
I'm 
> wondering if anyone else has seen this and if this is a bug or am I 
> missing a step. No errors are generated during the warp setup and
execution.

Brian,

I'm not sure how you are warping directly to PNG or JPEG.  These are
both
"createcopy" formats, that have to be written out sequentially from an
input file.  The warper cannot normally use these formats at all as
direct
output formats.  How did you?

Can you provide a specific example demonstration with the gdalwarp
commandline program?  If so, could you file it in bugzilla?

Best regards,
-- 
---------------------------------------+--------------------------------
------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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