Runs Tesseract on the given image, via stdin/stdout, producing hOCR data.
Runs Tesseract on the given image, via stdin/stdout, producing hOCR data.
The retval's standardOutput will contain the hOCR data.
The Future may be a Failure, too, in the following cases:
* TesseractMissingException if options.tesseractPath does not point to an executable
* TesseractLanguageMissingException if Tesseract responded that a language could not be loaded
* TesseractUnknownException if retval != 0 (for no predictable reason) -- message will contain stderr output