fax: Improve quality of grayscale to black-and-white conversion.
Sending faxes from material that is not pure back-and-white results in very bad image quality due to the way ghostscript rasterizes images by default. There are two things to improve the image quality:
- Use a different dithering algorithm
- Apply thresholds to map very bright colors to white and very dark colors to black:
I made a very simple test case:
The first line is pure black, second line is red, third line is a very dark gray.
Currently Roger Router produces this result:
With this change the result becomes:
