Important:
Image support in the documentation is somewhat experimental. The mechanisms described here are unlikely to change, but that is not guaranteed.
To provide conversion between different image formats, the graphics/ImageMagick port must be installed. This port is not included in the textproc/docproj meta port, and must be installed separately.
A good example of the use of images is the
doc/en_US.ISO8859-1/articles/vm-design/
document. Examine the files in that directory to see how
these elements are used together. Build different output
formats to see how the format determines what images are shown
in the rendered document.
The following image formats are currently supported. An image file will automatically be converted to bitmap or vector image depending on the output document format.
These are the only formats in which images should be committed to the documentation repository.
- EPS (Encapsulated Postscript)
Images that are primarily vector based, such as network diagrams, time lines, and similar, should be in this format. These images have a
.epsextension.- PNG (Portable Network Graphic)
For bitmaps, such as screen captures, use this format. These images have the
.pngextension.- PIC (PIC graphics language)
PIC is a language for drawing simple vector-based figures used in the pic(1) utility. These images have the
.picextension.- SCR (SCReen capture)
This format is specific to screenshots of console output. The following command generates an SCR file
shot.scrfrom video buffer of/dev/ttyv0:#vidcontrol -p</dev/ttyv0shot.scrThis is preferable to PNG format for screenshots because the SCR file contains plain text of the command lines so that it can be converted to a PNG image or a plain text depending on the output document format.
Use the appropriate format for each image. Documentation
will often have a mix of EPS and
PNG images. The
Makefiles ensure that the correct format
image is chosen depending on the output format used.
Do not commit the same image to the repository in
two different formats.
Important:
The Documentation Project may eventually switch to using the SVG (Scalable Vector Graphic) format for vector images. However, the current state of SVG capable editing tools makes this impractical.
Image files can be stored in one of several locations, depending on the document and image:
In the same directory as the document itself, usually done for articles and small books that keep all their files in a single directory.
In a subdirectory of the main document. Typically done when a large book uses separate subdirectories to organize individual chapters.
When images are stored in a subdirectory of the main document directory, the subdirectory name must be included in their paths in the
Makefileand theimagedataelement.In a subdirectory of
doc/share/imagesnamed after the document. For example, images for the Handbook are stored indoc/share/images/books/handbook. Images that work for multiple translations are stored in this upper level of the documentation file tree. Generally, these are images that can be used unchanged in non-English translations of the document.
Images are included as part of a mediaobject.
The mediaobject can contain other, more specific
objects. We are concerned with two, the
imageobject and the textobject.
Include one imageobject, and two
textobject elements. The imageobject
will point to the name of the image file without the
extension. The textobject elements contain
information that will be presented to the user as well as, or
instead of, the image itself.
Text elements are shown to the reader in several situations. When the document is viewed in HTML, text elements are shown while the image is loading, or if the mouse pointer is hovered over the image, or if a text-only browser is being used. In formats like plain text where graphics are not possible, the text elements are shown instead of the graphical ones.
This example shows how to include an image called
fig1.png in a document. The image is a
rectangle with an A inside it:
<mediaobject><imageobject><imagedata fileref="fig1">
</imageobject><textobject><literallayout class="monospaced">+---------------+| A | +---------------+
</literallayout></textobject><textobject><phrase>A picture</phrase>
</textobject></mediaobject>
| Include an |
| The first Notice how the first and last lines of the content
of the |
| The second |
Images must be listed in the Makefile
in the IMAGES variable. This variable must
contain the names of all the source
images. For example, if there are three figures,
fig1.eps, fig2.png,
fig3.png, then the
Makefile should have lines like this in
it.
… IMAGES= fig1.eps fig2.png fig3.png …
or
… IMAGES= fig1.eps IMAGES+= fig2.png IMAGES+= fig3.png …
Again, the Makefile will work out the
complete list of images it needs to build the source document,
you only need to list the image files you
provided.
Be careful when separating documentation into smaller files in different directories (see Section 7.7.1, “Using General Entities to Include Files”).
Suppose there is a book with three chapters, and the
chapters are stored in their own directories, called
chapter1/chapter.xml,
chapter2/chapter.xml, and
chapter3/chapter.xml. If each chapter
has images associated with it, place those images in each
chapter's subdirectory (chapter1/,
chapter2/, and
chapter3/).
However, doing this requires including the directory
names in the IMAGES variable in the
Makefile, and
including the directory name in the imagedata
element in the document.
For example, if the book has
chapter1/fig1.png, then
chapter1/chapter.xml should
contain:
<mediaobject><imageobject><imagedata fileref="chapter1/fig1"/></imageobject>…</mediaobject>
| The directory name must be included in the
|
The Makefile must contain:
… IMAGES= chapter1/fig1.png …