Version: 2019.2
public Texture mainTexture ;

Description

The graphic's texture. (Read Only).

This is the Texture that gets passed to the CanvasRenderer, Material and then Shader _MainTex. When implementing your own Graphic you can override this to control which texture goes through the UI Rendering pipeline. Bear in mind that Unity tries to batch UI elements together to improve performance, so its ideal to work with atlas to reduce the number of draw calls.