ST_SetPixelSize behaving unpredictably

[robe]

Okay perhaps it is my misunderstanding.

I have 2 elephants — one I brought in whole and one I chopped into pieces.

-- we let this one live
python gdal2raster.py -r pele.png -I -t ch13.pele -o pele.sql

- we sacrifice this one
python gdal2raster.py -r pele.png -I -k 50x50 -t ch13.pele_chunked -o pele_chunked.sql

Both come in upside down, which I assume is becasue I imported with gdal 1.6. No problem.

— run this command

UPDATE ch13.pele SET rast = ST_SetPixelSize(rast,1,-1);
UPDATE ch13.pele_chunked SET rast = ST_SetPixelSize(rast,1,-1);

The single row whole one flips over correctly to line up with the image as I expect. The second one just shifts down one row.

I would have expected the sacrificed elephant to also line up with the image after flipping.

See attached files.

[robe]

before

[robe]

after flip

[robe]

On closer inspection, I think this is just my misunderstanding. It seems that each tile is being flipped separately is all which makes perfect sense now that I think about it. I did a polygonize of each. I guess I have to change the upperleftx and upperlefty of each.

See attached.