Do indexed PNG 8s use less memory when utilized by XNA

Question

I'm working on an XNA project and running into issues involving memory usage. I was curious if using indexed color PNG 8s vs PNG 24s or PNG 32s for certain textures would free up any memory. It definitely makes the app smaller, but I'm curious if when XNA's content manager loads them they somehow become uncompressed or act as loss-less images.

Answer 1

I answered a similar question just recently.

If you want to save space when distributing your game, you could distribute your PNG files (you can also use jpeg) and load them with Texture2D.FromStream. Note that you'll have to handle things like premultiplied alpha yourself.

If you want to save space on the GPU (and this also improves texture-fetch because the amount of data transferred is smaller) you can use a smaller texture format. The list of supported texture formats is available in this table.

While there is no support for palletised images (like PNG8) or 8-bit colour images at all, there are several 16-bit formats (Bgr565, Bgra5551, Bgra4444). DXT compressed formats are also available. They compress at 4:1 ratio, except opaque DXT1, which is 6:1.

You can use both techniques at once.

Answer 2

Someone just pointed to me to this link on Facebook, immediately after I posted this question.

http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh855082%28v=vs.92%29.aspx

Apparently, in XNA, PNGs of any type become uncompressed in memory and I should look at using DXTs.