Derivative generation on Heroku (obsolete)
- Eddie Rubeiz
- Jonathan Rochkind
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
# | 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 |
All TIFFS work Removing | |
3 |
At some point in 2021, All TIFFS work | ||
4 |
PDFs work All TIFFS work Combined audio derivatives don’t work | ||
5 |
|
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 Colorspacecan be used to elucidate what happens to various types of original after being processed byvipsthumbnail.