Add simple test showing issues in grdimage #4204
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The plotting of this 5x5 PNG file reveals problems in master.
joa-quim
approved these changes
Sep 12, 2020
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The plotting of this 5x5 PNG file reveals problems in master. The original plots were made using the grdimage-part1 branch and make it clear the mismatches reported on #4163 is due to a (long-lived) bug in grdimage in master. Because those images are larger the offsets are very small, but this 5c5 revels a large shift, as indicated below (note: the shift only applies to the unprojected images on bottom row, not the Mercator projection on top row). It is clearly a pixel vs gridline-registration shift. While the PNG is pixel registered, in master it is treated as gridline and shifted by half a pixel.
Test output on the grdimage-part1 branch
Test output on the master branch