gl.useProgram( this.programMarker );
            gl.uniform1f( this.programMarker.sizeLocation, 2.0 );
            gl.runProgram( this.programMarker, this.ping.tex, null );
            //-------------------------------------------------------------------------------

            // read processed image pixels async through buffer
            //-------------------------------------------------------------------------------
            // gl.bindBuffer( gl.PIXEL_PACK_BUFFER, this.pbo );
            //
       