Using the following LaTeX-Code:
\documentclass[a4paper]{article}
\usepackage[pdf]{pstricks}
\usepackage{pst-barcode}
\begin{document}
\begin{pspicture}(0.7in,0.7in)
\psbarcode{01234567890}{eclevel=L}{qrcode}
\end{pspicture}
\end{document}
and pdflatex with "shell-escape" option
pdflatex -shell-escape QRCode.tex
a PDF containing the QR-Code is created. However, the QR-Code is anti-aliased. How can I turn off anti-aliasing?
I am using MacTeX (TeX-Live 2010) on Mac OS X 10.6
The Barcode Writer in Pure PostScript (BWIPP) library that pst-barcode uses would generate matrix-style barcodes using the PostScript imagemask operator which certain viewers (such as Preview on Mac) incorrectly* choose to interpolate.
For a bit of history, BWIPP switched away from the PostScript image operator in version 2008-12-07 because an increasing number of PS and PDF previewers began to interpolate its output. The replacement imagemask operator worked better for a time, but was clearly not perfect, so BWIPP has switched to using a filled path in version 2014-01-06 which should finally resolve the issue.
Until pst-barcode is updated, users who wish to use their existing pst-barcode with the latest version of BWIPP should replace their barcode.pro file with barcode.ps from the monolithic or monolithic-package distribution of BWIPP.
Update
This issue is resolved in pst-barcode 0.14.
Interesting Diversion
In a similar vein to Malipivo's intriguing answer which constructs a filled path using autotrace against the 2D barcode bitmap, BWIPP now includes a significant imaging improvement since version 2016-07-19.
Whereas the matrix renderer previously constructed the path-based image as a set of filled squares with each representing a single dark module of the symbol, we now construct the path as a minimal set of complex polygons describing the dark and light regions within the image – taking great care to handle the non-zero winding rule to ensure that enclosed regions are plotted correctly. This allows us to provide advanced imaging features such as compensating for inkspread in 2D barcodes by contracting the edges of dark regions by a fixed amount as described in this mailing list post.
The PostScript implementation of this can be seen here.
*: An imagemask should be applied as a bitmap stencil mask without "interpolation", unless requested.
AFAIK anti-aliasing is a feature of the PDF viewer and not influenced by LaTeX. You need to manually switch it off in your viewer. See also the related post My pixel perfect picture gets blurry when compiled in LaTeX, which is about images which look blurry.
Unrecommended way
I would like to share my solution for historical purposes only and as a new version of postscriptbarcode is not a part of the TeX distributions, yet (April 2014). The presented solution in this question works well for me.
I don't want to scare you, especially TeX beginners, but from time to time you might face a serious deadline even when working with TeX. It happened to me in November 2013 when a Mac OS X user complained about barcode preview in PDF and I had two hours to fix it before production and making PDF file publicly available. I needed solution fast and a working one on Windows, Linux and Mac OS X. I was permitted by publisher to use any (dirty) trick.
At that time I found patch for diff but I didn't tested that as there were so many different releases of this project. The official release solving the issue didn't exist at that time. I was thinking to convert the PDF file somehow. I tried Inkscape with no desired success. I had no time for pstoedit experiments.
As a FontForge user I started to think about raster to vector conversion. There are several projects, two major ones are autotrace and potrace. I installed them and started reading documentation followed by my first experiments.
Let me make this story short, I am presenting you a solution right away with GraphicsMagick + autotrace, where:
pst-barcode the usual way (auto-pst-pdf).-corner-surround 1 which helps to find 90 degree corners.\IfFileExists).The presented solution works for one page/barcode only, it would require additional setup for a temporary PDF file with more pages/barcodes. In addition to that, it would be possible to do such a conversion on-the-fly (\write18). As I am using primarily 90 degree corners, it may not work for other barcode types.
I run these commands (it works with pdf-, xe- and lualatex; TeX Live):
lualatex --shell-escape mal-qrcode.tex
gm convert mal-qrcode-pics.pdf mal-qrcode-pics.bmp
autotrace -output-format pdf -output-file pst-qr.pdf -corner-surround 1 -background-color FFFFFF mal-qrcode-pics.bmp
pdfcrop --hires --margins 0 pst-qr.pdf mal-qrcode-pics-vector.pdf
lualatex --shell-escape mal-qrcode.tex
I enclose the TeX file (mal-qrcode.tex) and a preview of the result in a web browser (Firefox using pdf.js). Picture on left introduces the problem, picture on right shows the solution.
%! *latex mal-qrcode.tex
% with shell escape on
\documentclass[a4paper]{article}
\pagestyle{empty}
\usepackage{pst-barcode}
\usepackage{auto-pst-pdf}
\pagecolor{blue}
\begin{document}
\def\malfile{mal-qrcode-pics-vector.pdf}
\begin{pspicture}(0.7in,0.7in)
\psbarcode{01234567890}{eclevel=L}{qrcode}
\end{pspicture}
\IfFileExists{\malfile}{\includegraphics{\malfile}}{%
% The pspicture environment goes here if we want permanent replacement...
}% End of \IfFileExists...
\end{document}
