[gdal-dev] JPEG2000 / GMLJP2: parameters seem to be ignored (offset location)

[Philippe Ghesquiere]

Hi all,

I have some questions about GMLJP2 parameters concerning location.


*1) Description*Some JP2K images have a pixel origin different than (0 ; 0)
(DIMAP products for example).

In such cases, the GML header looks like like:
<gml:GridEnvelope>
    *<gml:low>7 7</gml:low>  <========== Different than "0 0"*
    <gml:high>1000 1000</gml:high>
</gml:GridEnvelope>

This origin coordinate should be taken into account for pixel location (See
OGC 05-047r3  p93):
<element name="startPoint" type="gml:integerList" minOccurs="0">
    <annotation>
        <documentation>
             Index position of the first grid post, which
             shall lie somwhere in the GridEnvelope. If absent, the
startPoint is equal
             to the value of gridEnvelope::low from the grid definition.
        </documentation>
    </annotation>
</element>

It seems that this offset is not taken into account by GDAL location
function.

*2) How to reproduce*
2.1) Data creation
Reference (no offset) image:
gdal_create -of JP2OpenJPEG -co GMLJP2=YES -outsize 100 100 -bands 3 -burn
0 -burn 255 -burn 0 -a_srs epsg:32632 -a_ullr 500000 500100 500100 500000
Offset_0.jp2

Image with offset:
sed s/"<gml:low>0 0"/"<gml:low>7 7"/g Offset_0.jp2 > Offset_7.jp2

2.2) Location test
echo "0 0" | gdaltransform Offset_0.jp2 Offset_7.jp2
0 0 0

*3) Question:*
Shouldn't we have a 7 pixels offset between the 2 images

Cheers
Philippe
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