/usr/share/gem/examples/04.pix/ is in gem-doc 1:0.93.3-5ubuntu4.
This file is owned by root:root, with mode 0o755.
..
/usr/share/gem/examples/04.pix/01.image.pd
/usr/share/gem/examples/04.pix/02.multiimage.pd
/usr/share/gem/examples/04.pix/04.ImageInPlace.pd
/usr/share/gem/examples/04.pix/05.film.pd
/usr/share/gem/examples/04.pix/05.movie.pd
/usr/share/gem/examples/04.pix/06.PixRect.pd
/usr/share/gem/examples/04.pix/07.PixSet.pd
/usr/share/gem/examples/04.pix/08.PixDump.pd
/usr/share/gem/examples/04.pix/09.Histogram.pd
/usr/share/gem/examples/04.pix/10.PixDataSimple.pd
/usr/share/gem/examples/04.pix/11.PixDataComplex.pd
/usr/share/gem/examples/04.pix/12.add.pd
/usr/share/gem/examples/04.pix/12.blending.pd
/usr/share/gem/examples/04.pix/12.composite.pd
/usr/share/gem/examples/04.pix/12.pix_multiply.pd
/usr/share/gem/examples/04.pix/13.maskDancer.pd
/usr/share/gem/examples/04.pix/14.takeAlpha.pd
/usr/share/gem/examples/04.pix/15.pix_alpha.pd
/usr/share/gem/examples/04.pix/16.alphaGrey.pd
/usr/share/gem/examples/04.pix/16.pix_2grey.pd
/usr/share/gem/examples/04.pix/17.pix_gain.pd
/usr/share/gem/examples/04.pix/18.Curves.pd
/usr/share/gem/examples/04.pix/19.colorMatrix.pd
/usr/share/gem/examples/04.pix/20.convolve.pd
/usr/share/gem/examples/04.pix/22.biquad.pd
/usr/share/gem/examples/04.pix/23.gravity.pd
/usr/share/gem/examples/04.pix/24.time-filtering.pd
/usr/share/gem/examples/04.pix/25.buffer.pd
/usr/share/gem/examples/04.pix/26.framebuffer_readback.pd