List of ImageMagick types that should never be treated as images.
This should be a list of symbols, each of which should be one of
the ImageMagick types listed by `imagemagick-types'. The listed
image types are not registered by `imagemagick-register-types'.
If the value is t, inhibit the use of ImageMagick for images.
If you change this without using customize, you must call
`imagemagick-register-types' afterwards.
If Emacs is compiled without ImageMagick support, this variable
has no effect.