Using 16-Bit textures

WP7 textures are supported in the Reach-Profile that WP7 devices falls into. But XNA converts all my ressources upon adding them to a project to RGBA8, that's insane, the displays of WP7 devi开发者_如何学JAVAces are 16 Bit!

Information: WP7 SDK 7.1 (XNA 4), Visual Studio 2010

Question part 1: How can I add a RGB565 texture to a XNA project and what is the correct way to load them inside a game?

Question part 2: Is there a reasonable 16 Bit texture format (within Reach) that supports alpha with MORE than 1Bit?

Question part 3: Is the normal rendertarget (I think that's what the screenbuffer is?) already 16 bit?

Part 1:

change surfaceformat like graphics.PreferredBackBufferFormat = SurfaceFormat.Color; (XNA) OR (in Silverlight/XNA Project) SharedGraphicsDeviceManager.Current.PreferredBackBufferFormat = SurfaceFormat.Color; //supports 32bit ARGB each color 8bit

Part 2:

PNG should work... it supports 8bit (256) and 16Bit alpha channel(65.536 possibilities)