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I've got a lot of single-band Geotiff files with the GDT_Float32 format and I need to present these over the web, hopefully using a webmap leaflet/mapbox/googlemaps widget where clients can hover over the map and explore the values.

I've been looking at gdal2tiles.py but it resamples everything down to 8-bit png. Converting to 8-bit isn't going to work for me since I need to retain the precision.

Is there a solution out there for creating 32-bit png tiles for a web viewer? Should I be thinking about this another way?

  • Just out of curiosity, what sort of information does Geotiff store in the 32 bits? Is this 32-bit color? – barrycarter Apr 30 '16 at 18:06
  • It's a single band so that's functionally grayscale. Think a single 2D array filled with Float32. – Raychaser Apr 30 '16 at 19:10
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    OK, so you really have/need over 4 billion shades of gray? Most people can only distinguish like 50 (I've heard...) – barrycarter Apr 30 '16 at 20:24
  • A fair point. I think visually 255 values would be enough but I don't want to lose the actual values of the raster which correspond to experimental results. Maybe I need to store that information separately? Not really sure how though – Raychaser Apr 30 '16 at 23:46
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    Yeah, you just need to have a set of "original" files at 32-bit colour channels, and a set of "web-ready" files at 8-bit colour. Keep them separate, and have a script to quickly produce the 8-bit ones from the 32-bit ones. – IvanSanchez May 1 '16 at 13:02
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As per @IvanSanchez' suggestion I'm going g to have web-ready 8-bit rasters with accompanying json metadata files.

The metadata files have max and min values from the original 32-bit rasters which we use to interpolate the 0-255 values from the 8bit rasters so we can explore the values in real time.

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