[gdal-dev] Use of gdalwarp to make GeoTiff transparent is flipping the image

[Jukka Rahkonen]

Liglio <liglio <at> pobox.com> writes:


In your original file you have

> Origin = (-58.449520100000001,-34.571399100000001)
> Pixel Size = (0.020016536493374,0.020014199367660)

In the converted one you have

> Origin = (-58.449520100000001,-12.395666200632341)
> Pixel Size = (0.020015227575895,-0.020015227575895)

Notice the positive offset for the y coordinate in the original which means
that actually it is a south-up image and latitude is growing when you go
downwards from the up-most row of the image. Gdalwarp is turning the image
into common north-up image which is also changing the origin because the
native origin is now in the bottom-left corner.

If the original image is not really a south-up one then it has wrong
georeferencing. Gdalwarp is doing what it is supposed to do.

-Jukka Rahkonen-