Converts office files for Overview using LibreOffice.

Methodology

This program always outputs 0.json and 0.blob.

The output 0.json has wantOcr:false.

These metadata fields from the input document will be written to the output PDF:

• /Title
• /Author
• /Subject
• /Keywords
• /CreationDate
• /ModDate
• /Creator (program name that produced the document)

And these metadata fields will be written to the output JSON metadata (since there is no equivalent field in PDF):

• Modified By (akin to Author)
• Comments (text)

We use custom C++ with LibreOfficeKit and QPDF. This is painful and janky. Here's why:

• soffice.bin is slow to load, imposing big overhead (hence LOK).
• soffice.bin does not preserve metadata when converting to PDF (hence QPDF).
• soffice.bin cannot even extract metadata. The only move is to convert to .odt and then read the result as a zipfile -- costing a second invocation of soffice.bin just to read metadata (hence not using soffice.bin).

We create the LibreOffice profile directory once and reset it with every conversion. This is for security: once an invocation is complete, all its data is wiped.

Testing

Write to test/test-*. docker build . will run the tests.

Each test has input.blob (which means the same as in production) and input.json (whose contents are $1 in do-convert-single-file). The files stdout, 0.json and 0.blob in the test directory are expected values. If actual values differ from expected values, the test fails.

PDF is a tricky format to get exactly right. You may need to use the Docker image itself to generate expected output files. For instance, here is how we build test-odt/0.blob:

1. Wrote test/test-odt/{input.json,input.blob,0.json,stdout}
2. Ran docker build .. The end of the output looked like this: Step 12/13 : RUN [ "/app/test-convert-single-file" ] ---> Running in f65521f3a30c 1..1 not ok 1 - test-odt TODO do-convert-single-file wrote /tmp/test-do-convert-single-file912093989/0-thumbnail.jpg, but we expected it not to exist TODO ... TODO1. docker cp f65521f3a30c:/tmp/test-do-convert-single-file912093989/0-thumbnail.jpg test/test-jpg-ocr/ TODO1. docker rm -f f65521f3a30c