Loads the file by passing filename and flags to wxBitmap::LoadFile. If a bitmap had previously been specified with SetBitmap, that bitmap will no longer be used. If filename is NULL, then the current image is cleared.
If relativePath is TRUE and filename is a relative path, then the file will be read using the path of the owning buffer's filename.
If inline is TRUE, the image data will be saved directly to the file or clipboard when the image is saved or copied. The source filename is no longer relevant.