My pixel perfect picture gets blurry when compiled in LaTeX

This is just an effect of the display settings of your PDF viewer. In Acrobat Reader 9, for example, there is an option "Edit | Preferences | Page Display | Smooth images". If you uncheck this box, the picture will not be anti-aliased. When printing, your image should look fine regardless of the smoothing effect you see on screen.

Here's your file in Acrobat Reader 9, zoomed to 800%, left half with the default "Smooth images", right half with the option unchecked. Note the tick mark and the red X:

One option for forcing a pixel-perfect image in pdf viewers with unreliable interpolation settings is simply to scale the image up by a few multiples without interpolation, so that each pixel simply becomes several pixels on the new image. Then in latex, set the image scale to the inverse of the multiplier.

So, in the example below, I took the original, pixel-perfect image and scaled it up by 4x so that the result was 4 pixels per pixel in the original image. I then set the include scale to 0.25:

\includegraphics[scale=0.25]{wulfenbach.png}

This isn't perfect, but it is an improvement.

The reason this works is because the pdfviewer still does image interpolation as usual, but it does it over a larger image. So most of the "pixels" are now several real pixels wide, and mainly get blurred with themselves, so the apparent amount of antialiasing is smaller.

Here is a comparison on my system of the PDF output side by side with your original PNG. The PDF is on the left and the PNG on the right. I can see some slight differences, but I would not describe the PDF as blurrier.

PNG may be lossless, but it's still a bitmap format, and hence will look bad when zoomed in on, especially for a very small image like yours. Does Pixen have the option for exporting to a vector format, like EPS or PDF (or SVG, which you could then convert using other tools)? That would be better than PNG.