Relative Vs. Absolute Positioning For Image Annotations

Positioning Images and Annotations in LaTeX

The Core Problem: Absolute vs. Relative Positioning

When inserting images and adding annotations in LaTeX documents, a key consideration is whether to use absolute or relative positioning approaches. Absolute positioning precisely specifies the exact coordinates for images and annotations, while relative positioning defines placement in relation to nearby content.

LaTeX provides low-level commands to precisely set horizontal and vertical coordinates for images and text boxes. However, extensive use of absolute positioning makes documents less portable and more difficult to maintain. Small content changes may require manually updating many coordinate values.

In contrast, packages like wrapfig and picins allow wrapping text around figures and inserting annotations without hardcoding absolute coordinates. Images and annotations will remain properly positioned even if text length changes. However, this flexibility comes at the cost of less control over precise placement.

Tradeoffs Between Absolute and Relative Positioning

Using absolute positioning for images and annotations enables pixel-perfect precision in placing elements exactly where intended on the page. This grants full control over the appearance and layout.

However, any content additions or deletions that impact figure placements require manually updating absolute coordinate values. As a document grows in length and complexity, maintaining many absolute positions becomes increasingly tedious and impractical.

Conversely, leveraging relative positioning simplifies maintenance, allowing figures and annotations to automatically shift based on changes in surrounding text. But this fluidity means giving up precision, making it trickier to align elements or place them in an exact location.

Overall, absolute positioning excels for simpler, static documents where maintaining exact visual layout is critical. Relative positioning is better suited to long-form or frequently updated texts where flexibility trumps perfect precision.

Best Practices for Image Annotations

The TikZ package provides a robust tool for adding flexible annotations overlaid on images. TikZ offers fine control over annotation styles and connectors linking annotations to specific points on the figure.

Best practices when annotating images include:
- Place the image first using a figure environment, then overlay TikZ nodes on top for annotations
- Customize connectors between annotations and image points with arrows, lines or curves
- Consistently format annotations in terms of borders, backgrounds and font styles
- For complex annotation arrangements, define custom TikZ styles to simplify editing

Following these guidelines will help produce clean, polished annotated figures while avoiding common pitfalls like crossed connector lines, inconsistent styling, and tedious low-level coordinate tweaking.

Example Codes

Here is a basic example code for an image with a single anchored annotation:

\begin{figure}[h]
  \centering
  \includegraphics[width=0.8\linewidth]{image.png}
  \begin{tikzpicture}[remember picture,overlay]
    \node [draw=red, fill=blue!20] at (3,2.2) {Annotation Text};
    \draw[->,thick,red] (2.3,1.9) -- (2.8,2.15);
  \end{tikzpicture}
\end{figure}  

This overlays a rectangular node containing the annotation text, with a red arrow connector linking it to a point on the image.

A more advanced example with a figure subcaption and panel labels:

\begin{figure}[htbp]
  \centering
  \begin{subfigure}[b]{0.48\linewidth}
    \includegraphics[width=\linewidth]{plot1}
    \label{fig:a}
  \end{subfigure}
  \hfill
  \begin{subfigure}[b]{0.48\linewidth}
    \includegraphics[width=\linewidth]{plot2}
    \label{fig:b}
  \end{subfigure}
  
  \begin{tikzpicture}[remember picture,overlay]
    \draw[->,ultra thick,blue](1.5,2.8) to[out=0,in=180] (3,3.2);
    \node[below right] at (2.25,2.3) {Transition point};
  \end{tikzpicture}
  
  \caption{Demonstration of effect\label{fig:demo}}
\end{figure}  

Here panel labels facilitate subplot references while the overlay annotation highlights a key feature.

Recommendations for Common Use Cases

For research papers and technical reports, consistent, standardized figure captions and annotations are critical:

• Use relative positioning to keep figures organized even during revisions
• Link labels clearly to highlighted elements with leader lines
• Format labels uniformly for professional appearance

In textbooks and documentation with many graphical explanations:

• Overlay annotations directly on illustrations to integrate text and graphics
• Leverage styles and reusable macros to maintain consistency
• Use annotations to actively guide readers through key points

For presentation slides and handouts, clarity and visual focus are most important:

• Use sparse annotations judiciously to avoid overwhelming slides
• Allow liberal white space around figures and annotations
• Combine TikZ overlay code with beamer slide templates for integrated style

Conclusion and Final Thoughts

Determining optimal positioning approaches depends greatly on the use case. For precision and control, absolute coordinates may be warranted. In complex, shifting documents, relative positioning simplifies maintenance.

TikZ provides extremely versatile tools for overlaying annotations while linking them visually to figure elements. Following best practices for consistent format and legible structure, annotations can greatly improve reader engagement and comprehension.

By understanding positioning tradeoffs and leveraging packages like TikZ, LaTeX enables authors to deploy annotated figures that distill insights clearly while integrating smoothly into diverse documents.