




The 
convert-external-image
 function returns an image derived from 
external-image
. The image is ready for drawing to the given graphics port. 
If 
cache
 is non-
nil
 image conversions are cached in the 
external-image
. The default value of 
cache
 is 
nil
.
If 
force-new
 is non-
nil
 a new image is always created, and put in the cache. The default value of 
force-new
 is 
nil
.