At a fundamental level everything that is seen on a display device is represented as either a vector or raster image. These images can be stored as stand alone documents or embedded within a more complex document format capable of containing many other types of information.

A raster image's structure closely matches it's representation as shown on modern display hardware; the image is represented as a grid of filled square ``pixels''. Each pixel is considered to be a filled square of the same size and contains information describing its colour. This representation is simple and also well suited to storing images as produced by cameras and scanners.

The drawback of raster images is that by their very nature there can only be one level of detail. Figures \ref{vector-vs-raster} and \ref{vector-vs-raster-scaled} attempt to illustrate this by comparing raster images to vector images in a similar way to Worth and Packard\cite{worth2003xr}.

Consider the right side of Figure \ref{vector-vs-raster}. This is a raster image which should be recognisable as an animal defined by fairly sharp edges. Figure \ref{vector-vs-raster-scaled} shows that zooming on the animal's face causes these edges to appear jagged. There is no information in the original image as to what should be displayed at a larger size, so each square shaped pixel is simply increased in size. A blurring effect will probably be visible in most PDF viewers; the software has attempted to make the ``edge'' appear more realistic using a technique called ``antialiasing'' (See Section \ref{Straight Lines}).\footnote{The exact appearance of the images at different zoom levels will depend greatly on the PDF viewer or printer used to display this report. On the author's display using the Atril (1.6.0) Document viewer, the top images appear to be pixel perfect mirror images at a 100\% scale. In the bottom raster image, antialiasing is not applied at zoom levels above $125\%$ and the effect of scaling is quite noticeable.}

%\footnote{\noindent This behaviour may be configured in some PDF viewers (Adobe Reader) whilst others (Evince, Atril, Okular) will choose whether or not to bother with antialiasing based on the zoom level. For best results experiment with changing the zoom level in your PDF viewer.\footnotemark}\footnotetext{On the author's hardware, the animals in the vector and raster images should appear mirrored pixel for pixel; but they may vary slightly on other PDF viewers or display devices.}

In contrast, the left sides of Figures \ref{vector-vs-raster} and \ref{vector-vs-raster-scaled} are a vector image. A vector image contains information about a number of geometric shapes. To display this image on modern display hardware, the coordinates are transformed according to the view and \emph{then} the image is converted into a raster like representation. Whilst the raster image merely appears to contain edges, the vector image actually contains information about these edges, meaning they can be displayed ``infinitely sharply'' at any level of detail\cite{citationneeded} --- or they could be if the coordinates are stored with enough precision (see Section \ref{}). Thus, vector images are well suited to high quality digital art\footnote{Figure \ref{vector-vs-raster} is not to be taken as an example of this.} and text.


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\settoheight\imageheight{\includegraphics{figures/fox-raster.png}}
\settowidth\imagewidth{\includegraphics{figures/fox-raster.png}}

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\begin{figure}[H]
	\centering
	\includegraphics[scale=0.7528125]{figures/fox-vector.pdf}
	\includegraphics[scale=0.7528125]{figures/fox-raster.png}
	\caption{Original Vector and Raster Images}\label{vector-vs-raster}
\end{figure} % As much as I hate to break up the party, these fit best over the page (at the moment)
\begin{figure}[H]
	\centering
	\includegraphics[scale=0.7528125, viewport=210 85 280 150,clip, width=0.45\textwidth]{figures/fox-vector.pdf}
	\includegraphics[scale=0.7528125, viewport=0 85 70 150,clip, width=0.45\textwidth]{figures/fox-raster.png}
	\caption{Scaled Vector and Raster Images}\label{vector-vs-raster-scaled}
\end{figure}
