PDF to EPUB Conversion Tools Score Low on Accuracy in VIGC Test

“A good example is the combination of the letters ‘f’ and ‘I’,” continues Hagen. “In the text we wrote, there were the word profiles where the ‘f’ and ‘i’ were replaced by one glyph, the ligature. But in some EPUB files we found ‘profles’ instead of profiles’—the ‘i’ had been dropped.

“Some conversion tools didn’t recognize the ligature and made an incorrect conversion. The automatic use of ligatures is the default in Adobe InDesign—i.e. InDesign will automatically replace certain combinations with the ligature—so you can imagine how often this happens in a document, and how often this will go wrong with some tools. You need to scan the converted files manually to check for missing letters, which simply isn’t feasible.”

Validation misses the mark
According to Hagen, validation tools pose an even bigger problem. “What amazed us the most was the validation of the EPUB files. Validation was a standard practice in our test, a simple way to partially check the quality of the conversion. We used four different validation tools and got different results.