# First use of mathbbm prints out unreadable

When applying \mathbbm to a letter for the first time in a document and then producing a PDF, the letter appears correct on the screen but is shaded away and almost unreadable on a printout from a printer. This only applies to the very first letter \mathbbm is applied to in a document. Has anyone had the same problem? Does anyone know how to fix it?

Here is an MWE:

\documentclass[a4paper,11pt,oneside]{article}
\usepackage{bbm}

\begin{document}
$$\mathbbm{P}[X]=\frac{1}{2}$$
$$\mathbbm{N}$$
\end{document}


The P appears normal when the PDF is viewed on the screen but once the document is printed off, it is shaded. The N, however, prints out correctly.

• Welcome to TeX.SE...Can you post your code as MWE? It will helps to do a detailed analysis... – MadyYuvi Sep 5 '19 at 9:21
• (1) Welcome, to TSE, (2) can you please provide some code that generates a document what when printed should give this. I've never heard of such a problem before. – daleif Sep 5 '19 at 9:22
• The font used by \mathbbm is only available in bitmap form, so it will be jagged on high resolution printers. – egreg Sep 5 '19 at 10:23
• Thank you very much for the comments, I've added an MWE to the question. – Mikolaj Sep 6 '19 at 7:36

This is the image of the output I get from your example, taken from a magnified view.

You can clearly see that the letters P and N from the bbm font are jagged, whereas the others characters show very cleanly.

The fonts used by the bbm package are only available as bitmaps. The package hasn't been maintained for 20 years.

Note that the P has “more chances” to be printed badly, because of the curve. To the contrary, N has mostly straight paths.

You may be able to reduce the amount of jagging by adding

\pdfpkmode{ljfzzz}
\pdfpkresolution=1200


at the very beginning of your document (see https://tex.stackexchange.com/a/336216/4427). Resolution can also be made higher, but for your printer 1200 should suffice.

In my opinion it's better to switch to a different “blackboard bold” font.