Hi,
I've found a possible bug in GDAL 2.1 RC4 and the MBTiles driver.
I have the following image that I'm geo referencing: http://imgbox.com/tLFn3Auq
If I'm using the follwing code to warp the image based on a GeoTransform, it works well: https://gist.github.com/gunnarblom/9d73aa4358f3dafe2fd6808f7d4e9f41
...and it produces the following image which is correct: http://imgbox.com/TrzlXk4P
(note: as the target coordinate system is Apple's own in MapKit, the y-axis is reversed and therefor the negation of the two last parameters in the GeoTransform before warping)
If I'm using the following code to create MBTiles: https://gist.github.com/gunnarblom/76364b6bc8c0ff48dcf9fb81a5fdc060
...but for some images/GeoTransforms it produces artifacts: http://imgbox.com/Gd15nfaP (three artifacts along the sides)
(note: this GeoTransform is based on WGS84-coordinates instead of Apple's coordinate system above in the regular image warp)
This error can be very strong on other images, it seems stronger the more skewed the transform is (example with a dummy-test I did with a random image: http://imgbox.com/FAWJj0eC)
What do you think can cause this bug?
Thanks!
Regards,
Gunnar
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