Control the export of WMF images

Padmasiri e-mailed me from Sri Lanka:

“I draw diagrams in AutoCAD and export them as Windows Metafiles(WMF). After that I import them to an MS Word document. Unfortunately they are imported with the background. But I want them without background (only the line work). How do I overcome this problem?”

This is a common task. You create WMF files by choosing File>Export. WMF is a vector format, so it’s ideal for creating images from AutoCAD objects. By default, you should not get the background. The system variable WMFBKGND controls the background. Set it to Off to make the background transparent. This is the default value, so either it was changed, or perhaps the version of AutoCAD is pre-release 2000.

Another system variable, WMFFOREGND, works only when WMFBKGND is Off and controls the line color. By default it’s value is 0, which swaps the foreground and background colors to make the objects darker than the background. If you use a black screen and your object is white, you don’t want the object to export as white, but as black. So AutoCAD would convert the black to white and vice versa.

With WMFBKGND at its default Off value, here is a cylinder after inserting it into a Microsoft Word document. I used a black drawing area.

With WMFBKGND set to On, here is the result:

Notice the large area included in the image in both cases, even though I only selected the cylinder. You get rid of this by displaying the Picture toolbar in Word and using the Crop button, like this (done with WMFBKGND set back to Off):

By default, the image doesn’t cover the text, so although the background is white, you can’t tell if it’s transparent. If you want to overlay text, double-click the image to open the Format Picture dialog box and click the Layout tab. You can choose the Behind Text or the In Front of Text option.

I chose the Behind Text option and formatted the text to be more legible. Here you can see that the background of the image is transparent, because the text and the image overlap.

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