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77 lines
2.2 KiB
Markdown
77 lines
2.2 KiB
Markdown
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title = "Extract Text from Files"
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weight = 120
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# Context and Problem Statement
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With support for more file types there must be a way to extract text
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from all of them. It is better to extract text from the source files,
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in contrast to extracting the text from the converted pdf file.
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There are multiple options and multiple file types. Again, most
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priority is to use a java/scala library to reduce external
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dependencies.
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# Considered Options
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## MS Office Documents
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There is only one library I know: [Apache
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POI](https://poi.apache.org/). It supports `doc(x)` and `xls(x)`.
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However, it doesn't support open-document format (odt and ods).
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## OpenDocument Format
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There are two libraries:
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- [Apache Tika Parser](https://tika.apache.org/)
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- [ODFToolkit](https://github.com/tdf/odftoolkit)
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*Tika:* The tika-parsers package contains an opendocument parser for
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extracting text. But it has a huge dependency tree, since it is a
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super-package containing a parser for almost every common file type.
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*ODF Toolkit:* This depends on [Apache Jena](https://jena.apache.org)
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and also pulls in quite some dependencies (while not as much as
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tika-parser). It is not too bad, since it is a library for
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manipulating opendocument files. But all I need is to only extract
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text. I created tests that extracted text from my odt/ods files. It
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worked at first sight, but running the tests in a loop resulted in
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strange nullpointer exceptions (it only worked the first run).
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## Richtext
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Richtext is supported by the jdk (using `RichtextEditorKit` from
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swing).
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## PDF
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For "image" pdf files, tesseract is used. For "text" PDF files, the
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library [Apache PDFBox](https://pdfbox.apache.org) can be used.
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There also is [iText](https://github.com/itext/itext7) with a AGPL
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license.
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## Images
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For images and "image" PDF files, there is already tesseract in place.
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## HTML
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HTML must be converted into a PDF file before text can be extracted.
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## Text/Markdown
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These files can be used as-is, obviously.
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# Decision Outcome
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- MS Office files: POI library
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- Open Document files: Tika, but integrating the few source files that
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make up the open document parser. Due to its huge dependency tree,
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the library is not added.
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- PDF: Apache PDFBox. I know this library better than itext.
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