$ VIPS_TRACE=1 irb
irb(main):001> require 'vips'
=> true
irb(main):002> x = Vips::Image.black 10, 10
irb(main):003> x.pngsave "x.png", keep: [:icc, :xmp]
vips cache*: cast in=((VipsImage*) 0x63d8ec4851c0) out=((VipsImage*) 0x63d8ecc90770) format=((VipsBandFormat) VIPS_FORMAT_UCHAR) shift=FALSE -
vips cache : copy in=((VipsImage*) 0x63d8ecc90770) out=((VipsImage*) 0x63d8eca264f0) -
vips cache+: cast in=((VipsImage*) 0x63d8eca264f0) out=((VipsImage*) 0x63d8ec583ca0) format=((VipsBandFormat) VIPS_FORMAT_UCHAR) -
vips cache+: colourspace in=((VipsImage*) 0x63d8eca264f0) out=((VipsImage*) 0x63d8ec47f0e0) space=((VipsInterpretation) VIPS_INTERPRETATION_B_W) -
vips cache : pngsave in=((VipsImage*) 0x63d8ec4851c0) filename="x.png" keep=((VipsForeignKeep) VIPS_FOREIGN_KEEP_XMP | VIPS_FOREIGN_KEEP_ICC) -
=> nil

image.pngsave "x.png", keep: :icc
image.pngsave "x.png", keep: "icc xmp"
image.pngsave "x.png", keep: ["icc", "xmp"]
image.pngsave "x.png", keep: [1 << 3, 1 << 1]

module Vips
  # Savers can be given a set of metadata items to keep.
  #
  # *   `:none` remove all metadata
  # *   `:exif` keep EXIF metadata
  # *   `:xmp` keep XMP metadata
  # *   `:iptc` keep IPTC metadata
  # *   `:icc` keep ICC profiles
  # *   `:other` keep other metadata

  class ForeignKeep < Symbol
  end
end