Opinion of 8-bit PNG for Orthophotos

I generated a tilemap from a large orthophoto using gdal2tile. Looking at a file of 256x256 at dense areas, file sizes above 150kb.

This adds up a bit when loading many tiles when i compared to bingmaps etc (below 100kb) .

Tested a few tiles, i converted it to PNG 8-bit format using paint.net

Visually it looks the same but the file sizes are 1/3 of the original.

My question are

  1. Is it accepted to use 8-bit PNG. The original file is a colored orthophoto of a city.

  2. Reading up on transparency, it seems 8-bit supports it. It is needed in my application.


Cesium supports any PNG image. Second part is out of the scope of Cesium, but transparency is only preserved in 32-bit when I save out a file in paint.net.