Derivative generation on Heroku

Types of original images in the digital collections

TIFF
- Black and white colorspace
- RGB colorspace
PDF

Diagnostics for derivative generation software

Run the following commands in a heroku dyno. Your results may vary slightly, but anything that is way off should be seen as a red flag.

heroku run bash

mediainfo --version
# Normal output:
# MediaInfo Command line,
# MediaInfoLib - v19.09

convert -version
# Normal output:
# Version: ImageMagick 6.9.10-23 Q16 x86_64 20190101 https://imagemagick.org
# Copyright: © 1999-2019 ImageMagick Studio LLC
# License: https://imagemagick.org/script/license.php
# Features: Cipher DPC Modules OpenMP
# Delegates (built-in): bzlib djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl lzma openexr pangocairo png tiff webp wmf x xml zlib

pdfunite -v
# Normal output:
# pdfunite version 0.86.1

vips --version

# Normal output:
# vips-8.10.6-Tue Mar 23 20:52:58 UTC 2021

vips -l | grep -o '[a-z_]*pdf[a-z_]*'
# Normal output:
# pdfload_base
# pdfload
# pdf
# pdfload_buffer
# pdfload_source

cd tmp

PROFILE=`ls ../vendor/bundle/ruby/*/gems/kithe-*/lib/vendor/icc/sRGB2014.icc`
wget https://digital.sciencehistory.org/downloads/m3zcuho -O b_w.tiff
wget https://digital.sciencehistory.org/downloads/1h16b9n -O color.tiff
wget https://digital.sciencehistory.org/downloads/519ucnx -O normal.pdf

vipsthumbnail  color.tiff  --eprofile $PROFILE
vipsthumbnail  b_w.tiff    --eprofile $PROFILE
vipsthumbnail  normal.pdf

identify *.jpg | grep sRGB

# Normal output (ignore warnings):
# tn_b_w.jpg    JPEG 128x108 128x108+0+0 8-bit sRGB 23603B 0.000u 0:00.000
# tn_color.jpg  JPEG 128x96 128x96+0+0   8-bit sRGB 11880B 0.000u 0:00.000
# tn_normal.jpg JPEG 99x128 99x128+0+0   8-bit sRGB  1619B 0.010u 0:00.000

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

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.