Colorize external pictures using pdflatex

Question

I have several greyscale-pictures that I would like to get colorized within pdflatex (so it will be automatically colorized to a given color, from black-to-white lets say black-to-red).

Is there a way to manipulate external graphics in pdflatex directly?

If this is not possible what way would you recommend to do this for a hundreds of pictures on a linux system? (maybe imagemagick?)

Example:

Should be something like:

Answer 1

As far as I know, you can't alter raster images in LaTeX itself. You can, however, call ImageMagic, like you suggested, to transform the image just before it's included. Here's a macro that allows you to write

\redify{image.jpg}

to convert and include the image (shown here in comparison to the unaltered image which is included using \includegraphics{image.jpg}:

ImageMagick is called every time the \redify macro is called, regardless of whether the image has already been converted. If you have many and very large images, you might want to compile the document once with the conversion enabled, and comment out the conversion line from the macro on subsequent runs:

\documentclass{article}
\usepackage{graphicx}
\newcommand{\redify}[2][]{%
\immediate\write18{convert #2 -fill red -tint 40 blurred#2}%
\includegraphics[#1]{blurred#2}%
}

\begin{document}
\includegraphics{image.jpg}\redify{image.jpg}
\end{document}

Answer 2

This answer is an improvement of Jakes previous answer, please read his answer if you're not satisfied with mine.

Using ImageMagick is probably the only way of manipulating raster pictures the way I need.

This output is produced by putting

\includegraphics{image.jpg}\redify{image.jpg}

But as Jake mentioned there could be a speed problem:

ImageMagick is called every time the \redify macro is called, regardless of whether the image has already been converted. If you have many and very large images, you might want to compile the document once with the conversion enabled, and comment out the conversion line from the macro on subsequent runs.

Therefore I added the executeifnewer-routine that will check if the source image is newer than the redified one. If so, it will call the conversion, and if not, it will just include the picture. This might save you much time and can easily ported to other (not only conversation) applications.

Here is the code:

\documentclass{article}
\usepackage{graphicx}
\newcommand{\executeifnewer}[3]{%
  \ifnum\pdfstrcmp{\pdffilemoddate{#1}}{\pdffilemoddate{#2}}>0%
  {\immediate\write18{#3}}%
  \fi}

\newcommand{\redify}[2][]{%
  \executeifnewer{#2}{blurred#2}{convert #2 -fill red -tint 40 blurred#2}%
  \includegraphics[#1]{blurred#2}%
}

\begin{document}
\includegraphics{image.jpg}\redify{image.jpg}
\end{document}