Graphics, Figures & Tables ⇒ Avoid png resampling by pdfLaTeX

[qubyte]

Hello all. This is my first post so I hope I'm not going to ask something stupid.

I have some code that is generating bitmaps for me (pseudocolor plots), and I'm using pgfplots to wrap the bitmap portion in nice axes etc. These bitmaps that I'm producing are saved as png files so that they don't suffer from compression. However, when pdflatex compiles a document with a png in it, it resamples the graphic. I'd like to be able to include the png file in such away that nothing is added or taken away. I'm a bit OCD about information being added or taken away from plots...

As a simple example:

Code: Select all

\documentclass{article}
\usepackage{graphicx}
\begin{document}
\includegraphics{124_cropped}
\end{document}

The attached file is an example png. Compare the png with the generated pdf at the pixel level of the png.

Ultimately this is not a deal breaker for me, but it would be nice to see the plot I generated come out of the process without being mangled. If there is an easy way of avoiding this, perhaps by converting the png to a pdf in a lossless manner first, then I'd appreciate any advice.

Thanks!

[frabjous]

Does whatever program you're using to generate the PNG have the option to output to a vector format like PDF or EPS instead?

[qubyte]

I'm using Matlab for this, and it seems not without the same thing happening. Even if I could, I need to crop the output to get rid of whitespace and this is only practical with a bitmap as far as I know. I guess fiddling around with the bounding box of an eps is an option if I could get a nice plot in that format. I'll check this tomorrow at work.

That aside, I'd still like to know if there's a way of getting a png into a document without it being altered.

[frabjous]

I've never noticed the problem you're discussing personally, so I don't know what's causing it, but I don't understand how the problem would also apply to eps or pdf figures, since the concept of "resampling" doesn't apply to vector graphics.

You should be able to crop pdf graphics using the pdfcrop perl script that came with your LaTeX distribution. (Personally I'd just convert eps to pdf for use with pdflatex using epstopdf from ghostscript, which you probably already have installed.) If you need a GUI, you could use BRISS.

[qubyte]

Ah, you see, normally I'm a vector graphic purist. However, this is one of the few cases when a raster graphic is better. The bitmap contains exactly the right information, and a vector graphic version is only going to be bloated and scrolling the resultant pdf will be laggy. No, I want this to be raster graphic. PDF and EPS can serve as containers for those (of course) so this is the optimal solution.

[qubyte]

This is why I'm using pgfplots to contain the bitmap. Then I get all the vector graphic goodness from the box around the plot outwards. The best of both worlds!

I've attached an example pdf of what comes out of this arrangement. Using a vector version of the pseudo colour plot would have resulted in the pdf being several MB in size, and added nothing. Whilst this looks grainy, that's because I've had to calculate each pixel. A future version of this plot will be higher resolution most probably and even if it's not, this is how it is supposed to look.

[localghost]

In case this represents a solution, please mark the topic accordingly as written in Section 3 of the Board Rules (to be read before posting).


Best regards and welcome to the board
Thorsten

[qubyte]

This is not a solution. The problem remains open; I've simply demonstrated what I'm doing and why it is important.

I read the board rules before posting.

Cheers

[qubyte]

Ok, so I just took a look at this again, and it turns out there was a problem, just not where I was looking.

The problem is actually in Preview in OSX. It displays the png files properly, but with pdf files it interpolates for no reason. Opening this up in Acrobat Reader revealed that the pdf files that I've produced are in fact totally fine.

Macs... -_-