Basemapper sometimes has mixed jpg and png images

[spwoodcock]

Describe the bug

Issue from #266

Tile data comparison

• osm-fieldwork generates the tile table with mixed png / jpg data.
• There are also some rows with missing data.

• QGIS generates consistent image format, depending on what is specified.
• There are no rows with missing data.

Image comparison

• The quality of the embedded images is the same between QGIS and osm-fieldwork.
• The correct data is inserted in the right place:

Possible solutions

• Add image conversion jpg --> png and vice versa.
• Do not append rows with empty data.

[rsavoye]

Basemapper shouldn't be a mix of pngs and jpgs when using the same upstream source. The suffix is defined in the imagery.yaml file, and shouldn't ever change when downloading tiles. Empty rows are from networking issues with the imagery server. I often have to run basemapper 2-3 times to get everything, but it should be easy to add support to try a tile again if there are networking issuses, which would eliminate the empty tiles.

[spwoodcock]

I should have clarified to say this is for a TMS source

[spwoodcock]

Perhaps we should add a provider "oam" that is specifically configured to work well with OAM.

TMS can be quite varied, with metadata available and xy ordering.

OAM for example uses the swapped --xy format

[rsavoye]

There is an oam in imagery.yaml. I only used it for the Turkey earthquake, but didn't see any issues with mixing png and jpgs. The swapped xy is what forced me to add that setting in the config file.

[spwoodcock]

I can confirm this is only for custom TMS from OpenAerialMap.

Perhaps it's a big with OAM providing mixed image types?

Need to confirm.