When JMP mapping, how can I load an image with a transparent background to keep the background transparent?

[#1]

JMP maps the following JSL and then loads the transparency image with a transparent background.

Save as a new image, how to use JSL?

dt=Open("$SAMPLE_DATA/Big Class.jmp");
p1 = dt << Graph Builder(
	Variables( X( :weight ), Y( :height ), Group X( :age ), Color( :sex ) ),
	Elements( Bar( X, Y, Legend( 5 ), Response Axis( "X" ) ) )
);

Thanks!

[#2]

Maybe something like this

When exporting graph as image the background of the graph box remains white even when set as "transp... 

There is also a wish list item Transparent background color for graphs