Comment # 11 on bug 1088463 from Petr Gajdos

On the system with ghostscript fonts installed:

$ convert /home/abuild/rpmbuild/BUILD/ImageMagick-7.0.7-28/images/logo.jpg
-annotate +0+10 'logo' logo-annotated.jpg
$ identify logo-annotated.jpg
logo-annotated.jpg JPEG 123x118 123x118+0+0 8-bit sRGB 18999B 0.000u 0:00.000
$

On the system without ghostscript fonts installed (just dejavu-fonts there per
corresponding build requires):

$ convert /home/abuild/rpmbuild/BUILD/ImageMagick-7.0.7-28/images/logo.jpg
-annotate +0+10 'logo' logo-annotated.jpg
convert: unable to read font `helvetica' @
error/annotate.c/RenderFreetype/1432.
$

So some sort of fallback is used, which is not translated to correct font file,
it seems. Obviously FT_Open_Face() is not supposed to handle such sort of
fallback.

Just note, on both systems obviously:

$ fc-match helvetica
DejaVuSans.ttf: "DejaVu Sans" "Book"
$