Archive | September, 2016

How to convert images to PDF with paper and image size, without ImageMagick

ImageMagick’s convert tool is handy for converting a series of images into a PDF. Just for future reference, here is one method how you can achieve the same without convert. It is useful if you have 1-bit PBM images (e.g. scanned text) at hand:

This command concatenates all .pbm files, pipes the data to pnmtops to create an […]

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Digitizing books 
(International Dunhuang Project, CC BY-SA 3.0)

Digitize books: Searchable OCR PDF with text overlay from scanned or photographed books on Linux

Here is my method to digitize books. It is a tutorial about how to produce searchable, OCR (Optical Character Recognition) PDFs from a hardcopy book using free software tools on Linux distributions. You probably can find more convenient proprietary software, but that’s not the objective of this post. Important: I should not need to mention that depending […]

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'Hashed' brown potatoes. Hashing is important on more than just one level (picture by Jamie Davids, CC-BY-2.0)

Hashing passwords: SHA-512 can be stronger than bcrypt (by doing more rounds)

On a server, user passwords are usually stored in a cryptographically secure way, by running the plain passwords through a one-way hashing function and storing its output instead. A good hash function is irreversible. Leaving dictionary attacks aside and by using salts, the only way to find the original input/password which generated its hash, is to simply try all possible […]

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