From Xojo Documentation

Read-Only Property (As RGBSurface )
RGBSurfaceValue = aPicture.RGBSurface

Supported for all project types and targets.

Provides pixel-level access to the picture’s bitmap.


Used only for pictures built with the Picture constructor with a depth of 16 or 32, otherwise it returns Nil. Returns an RGBSurface object. Calling RGBSurface is a computer-intensive process. Use it to access individual pixels of the Picture image. It is extremely fast — faster than accessing pixels through the Graphics property.