\chapter{Images}

\section{To Convert a PDF to an Image}

\lettrine[]{U}{se} the \texttt{pdftoppm}\index{pdftoppm} command (from the \label{poppler-utils} \texttt{poppler-utils}\index{poppler-utils} package) to convert part or all of a pdf to an image. For example, to convert a pdf to a png: 

\begin{Verbatim}[]
pdftoppm input.pdf output -png
\end{Verbatim}

This will convert each page in the pdf to a png using the format ``output-01.png'' where ``01'' is the page number. To convert a single page of a multipage pdf, use the \texttt{-f} flag to specify which page to use. For example, this will convert page 5 to a png:

\begin{Verbatim}[]
pdftoppm input.pdf output -png -f 5 -singlefile
\end{Verbatim}

To convert a range of pages, use the \texttt{-f} flag to specify the first page to convert and use the \texttt{-l} flag to specify the last page of the range:

\begin{Verbatim}[]
pdftoppm input.pdf output -png -f 5 -l 10 -singlefile
\end{Verbatim}

The default resolution is 150 dpi. To change this, use the \texttt{-rx} flag to specify the resolution along the x-axis, and the \texttt{-ry} flag to specify the resolution along the y-axis;

\begin{Verbatim}[]
pdftoppm input.pdf output -png -rx 300 -ry 300
\end{Verbatim}

Doubling the resolution along both axes will increase the file size by an approximate factor of four, and will also increase the amount of detail in the image.

\ktcbox{When creating \LaTeX{} tutorials for the web, I will generally use the \texttt{standalone} class and then convert the resulting pdf to a png image for use with html.}

\section{To Extract Images from a PDF File}

\lettrine[findent=0mm]{T}{o} extract images from a pdf file, use the \texttt{pdfimages}\index{pdfimages} command (also from the same package\index{poppler-utils} mentioned in \S \ref{poppler-utils} ). As before, the \texttt{-f} flag denotes the first page you want to extract image files from and the \texttt{-l} flag denotes the last page to extract image files from. Omitting them both will extract images from all pages. 

By default, images are saved as PBM (for monochrome images), PGM (for grayscale images), or PPM (for color images) files. Use the \texttt{-j} flag to save them as \texttt{jpeg} files or the \texttt{-J} flag to save them as \texttt{jpeg 2000} files. 

The \texttt{-list} flag will send a list of image information to \texttt{stdout} including the image file name, the page number, the image dimensions and resolution, the color space type, and the color depth\index[concepts]{color depth}\index[concepts]{bits per component} (i.e., bits per component). If needed, this can redirected to a text file. To generate the list without generating any images, use the \texttt{-listonly} flag.


\section{This is just a test}

And this is just some text.