Fix high zoom 512/256 tile size #357
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We generate "overzoomed" tiles at the maximum zoom - i.e: if we normally generate 512px tiles, then at nominal zoom 16 we also generate 256px tiles. However, we were previously comparing nominal zoom with metatile coordinate zoom, and so were generating the 256px tiles for nominal zooms 13-16 (meta coord zooms 10-13). This fixes that issue, adds a test to catch regressions, and adds documentation explaining that the `max_zoom` parameter is coordinate zoom, not nominal zoom.
iandees
approved these changes
Nov 20, 2018
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The code was passing the coordinate max zoom to
calculate_sizes_by_zoom. For example, with 8x8 metatiles and a max nominal zoom of 16, it would pass 13. This meant that 256px tiles were being generated for 3 more zoom levels than we really needed.Added comments saying it's coordinate zoom and fixed the tests to pass in the coordinate zoom, with a one-line update to the method itself. This should mean we only get 256px tiles at max zoom, and not before.