Derivative generation on Heroku

Types of original images in the digital collections

TIFF
- Black and white colorspace
- RGB colorspace
PDF

Software needed to generate derivatives:

See Aptfile below.

Diagnostics for derivative generation software

These are now automated in a suite of tests you can run with. ./bin/rspec system_env_spec. See https://github.com/sciencehistory/scihist_digicoll/blob/master/system_env_spec/README.md .

See the page’s history for how we did this in the past.

Software setups

We’ve been through several of these since starting to investigate Heroku.

#	Aptfile	Buildpack	Results
1	libvips-tools mediainfo imagemagick poppler-utils	heroku-community/apt heroku/ruby	`vips-8.9.1-Sun Feb 23 08:51:26 UTC 2020` Color TIFFs work B&W TIFFs do not work PDFs work
2	libvips-tools mediainfo imagemagick poppler-utils	heroku-community/apt heroku/ruby	`vips-8.9.1-Sun Feb 23 08:51:26 UTC 2020` PDFs work All TIFFS work Removing `--eprofile srgb_profile_path` from the arguments to `vipsthumbnail` in the code (docs) avoids the error described in issue 942.
3	mediainfo imagemagick poppler-utils	heroku-community/apt https://github.com/machinio/heroku-buildpack-vips heroku/ruby	`vips-8.10.2-Mon Oct 12 16:43:59 UTC 2020` At some point in 2021, `vips -l \| grep -i pdf` started returning blank - no `poppler` support, so PDFs don’t work. All TIFFS work
4	mediainfo imagemagick libglib2.0-0 libglib2.0-dev libpoppler-glib8	heroku-community/apt https://github.com/brandoncc/heroku-buildpack-vips heroku/ruby	`vips-8.10.6-Tue Mar 23 20:52:58 UTC 2021` PDFs work All TIFFS work Combined audio derivatives don’t work
5	mediainfo imagemagick libglib2.0-0 libglib2.0-dev libpoppler-glib8	https://github.com/heroku/heroku-buildpack-activestorage-preview https://buildpack-registry.s3.amazonaws.com/buildpacks/heroku-community/apt.tgz https://github.com/brandoncc/heroku-buildpack-vips heroku/ruby	`vips-8.10.6-Tue Mar 23 20:52:58 UTC 2021` PDFs work All TIFFS work Combined audio derivatives work again (see issue 1448) `libpoppler-glib8` in the aptfile may not be needed (see issue 1455 )
6	`mediainfo` `imagemagick` `libglib2.0-0` `libglib2.0-dev` `libpoppler-glib8` `poppler-utils`	`https://github.com/heroku/heroku-buildpack-activestorage-preview` `heroku-community/apt` `https://github.com/brandoncc/heroku-buildpack-vips` `heroku/ruby`	PDF on-demand stopped working in staging, so we added poppler-utils back into aptfile.
7	`mediainfo` `imagemagick` `libglib2.0-0` `libglib2.0-dev` `libpoppler-glib8` `qpdf` `tesseract-ocr` `tesseract-ocr-eng` `tesseract-ocr-deu` `tesseract-ocr-fra` `tesseract-ocr-spa` `tesseract-error-while-loading-shared-libraries-libarchive-so-13-python` `libarchive13`	`heroku/python` `https://github.com/heroku/heroku-buildpack-activestorage-preview` `https://buildpack-registry.s3.amazonaws.com/buildpacks/heroku-community/apt.tgz` `https://github.com/brandoncc/heroku-buildpack-vips` `https://github.com/fnando/heroku-buildpack-exiftool` `heroku/ruby`	OCR. Note we are removing `poppler-utils`

Note: Row 2 was a band-aid; it violated the rule implicit in the code that all TIFF derivatives should have their derivatives encoded as srgb, including the derivatives of B&W originals. I interpret the documentation as meaning that the icc profile of originals is reused in their derivatives, but further research is needed.
identify -verbose graphics_file.tiff | grep Colorspace can be used to elucidate what happens to various types of original after being processed by vipsthumbnail.