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 |
Color TIFFs work PDFs work |
2 | libvips-tools mediainfo imagemagick poppler-utils | heroku-community/apt heroku/ruby |
All TIFFS work Removing |
3 | mediainfo imagemagick poppler-utils | heroku-community/apt https://github.com/machinio/heroku-buildpack-vips heroku/ruby |
At some point in 2021, 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 |
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 |
PDFs work All TIFFS work Combined audio derivatives work again (see issue 1448)
|
6 |
|
| PDF on-demand stopped working in staging, so we added poppler-utils back into aptfile. |
7 |
|
| OCR. Note we are removing |
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 byvipsthumbnail
.