Display images from a grid in an exported PDF

Is it me or can you not display images from a grid in an exported PDF? I have in onRecord Event

if ({field1} == '1')
	{
		{field1} = "<img src='../_lib/img/yes.png'/>";
			}
elseif ({field1} == '0')
	{
		{field1} = "<img src='../_lib/img/no.png'/>";
			}

In the grid it shows the images in each record row depending on the value of the field (1 or 0). When I export it to a PDF, regardless of the JS execution time (started at 2000 then set to 12000 and then down to 4000), I get little gray boxes where the images should be. Is it not possible to show images in a PDF? Seems like this should be standard functionality!