Figures much clearer in the internal PDF-Viewer

I have a problem:

In my thesis I added some figures via:

\begin{figure}[H]
\begin{center}
\includegraphics[width=\textwidth]{figure.png}
\caption{blablabla}
\label{Abb.1}
\end{center}
\end{figure}


My problem is, that the internal PDF-Viewer (I use TexMaker V4.1.1 under Debian Wheezy x64) displays the figures much, much clearer than any external PDF-Viewer.. But I am opening the same (!) file.

The following link shows a screenshot. On the left side one can see the internal Viewer from TexMaker and on the right side my external. http://i.imgur.com/Apia4fx.png

Thank you in advance!

Edit: What I have tried so far:

• As suggested here I installed cm-super. But it didn't change anything. (This might not have been the right approach.. I mean the fonts look fine, it's just the figures. But I wanted to try it anyway.)

• Also this solution didn't bring any changes...

-
Your pictures are bitmaps (.png) and so fonts doesn't matter. Recreate your pictures in a better quality (eg. as vector graphics). –  Ulrike Fischer Jan 29 at 11:14
It seems that Texmaker's viewers doesn't do antialiasing, while the external viewer does. –  egreg Jan 29 at 14:00
Thank you both! Thank you Ulrike, your workaround worked fine for me! And thanks egreg for pointing out the reason for the differences between those two appearances. –  Stephan Jan 29 at 14:58
Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. –  Martin Schröder Jan 30 at 9:50