Improve documentation of image conversion feature

* lisp/image/image-converter.el (image-converter)
(image-convert-p, image-convert):
* lisp/image.el (convert-images-externally):
* etc/NEWS:
* doc/lispref/display.texi (Defining Images): Fix recently
added documentation.

1 files changed, 2 insertions, 1 deletions

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index ec288b1c47d..a661eca13f0 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -6049,7 +6049,8 @@ If Emacs doesn't have native support for the image format in question,
 and @code{convert-images-externally} is non-@code{nil}, Emacs will try
 to determine whether there are external utilities that can be used to
 transform the image in question to @acronym{PNG} before displaying.
-GraphicsMagick, ImageMagick and ffmpeg are currently supported.
+GraphicsMagick, ImageMagick and @command{ffmpeg} are currently
+supported for image conversions.
 
 The function returns @code{nil} if images of this type are not
 supported.  Otherwise it returns an image descriptor.