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Basic Lua documentation. Requires expansion and re-work.
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Colin Clark
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| <?xml version="1.0" encoding="utf-8"?> | ||
| <section id="GuideReferenceLua"> | ||
| <title> | ||
| Lua Extensions | ||
| </title><para>Lua scripts allow the functionality of Geeqie to be extended. Lua scripts may only be used in conjunction with the Overlay Screen Display. | ||
| </para><para/> | ||
| <para>Some knowledge of the Lua programming language is required.</para> | ||
| <section id="Requirements"><title>Requirements</title><para>Use of Lua within Geeqie requires Lua 5.1 to be installed. If you are compiling from sources, Lua functionality will be available if the development files dependencies are met.</para> | ||
| <para>If you are using a pre-compiled distribution, availability depends on the package maintainer.</para></section> | ||
| <section id="HowToUseLua"><title>How to use Lua</title><para>Lua scripts must be stored in a single folder:<programlisting> | ||
| ~/.config/geeqie/lua/</programlisting></para> | ||
| <para>A link to a Lua script must be inserted into the overlay template. Refer to the Overlay Screen Display section of <link linkend="GuideOptionsWindow">Window Options</link>.</para> | ||
| <para>The full extent of the Lua language is available.</para></section> | ||
| <section id="GeeqieBuiltIn Functions"><title>Geeqie Lua built-in functions | ||
| </title><para>The following functions are built in to Geeqie:</para><para> | ||
| <informaltable><tgroup cols="2"><tbody><row><entry> | ||
| <emphasis role="strong">Function</emphasis> | ||
| </entry><entry> | ||
| <emphasis role="strong">Returns</emphasis> | ||
| </entry></row> | ||
| <row><entry> | ||
| Image:get_path() | ||
| </entry><entry> | ||
| The full path of the file, including filename and extension | ||
| </entry></row> | ||
| <row><entry> | ||
| Image:get_name() | ||
| </entry><entry> | ||
| The full filename including extension | ||
| </entry></row> | ||
| <row><entry> | ||
| Image:get_extension | ||
| </entry><entry> | ||
| The file extension including preceeding dot | ||
| </entry></row> | ||
| <row><entry> | ||
| Image:get_date() | ||
| </entry><entry> | ||
| The file date in Unix timestamp format. | ||
| </entry></row> | ||
| <row><entry> | ||
| Image:get_size() | ||
| </entry><entry> | ||
| The file size in bytes | ||
| </entry></row> | ||
| <row><entry> | ||
| Image:get_exif() | ||
| </entry><entry> | ||
| A data structure containing the entire exif data | ||
| </entry></row> | ||
| <row><entry> | ||
| <exif_str>:get_datum("<exif_tag>") | ||
| </entry><entry> | ||
| A single exif tag extracted from a structure output by the above command | ||
| </entry></row> | ||
| </tbody></tgroup></informaltable> | ||
| </para><para>The keyword "Image" refers to the file currently being displayed by Geeqie.</para></section> | ||
| <section id="Examples"><title>Examples | ||
| </title><para>The following example, which outputs the jpeg comment of a file, demonstrates the use of a built-in function and how to call a system command from a Lua script:<programlisting> | ||
| --Retrieve the jpeg comment of a file | ||
| path=Image:get_path() | ||
| commentfile=io.popen("exiv2 -p c \"" .. path .. "\"" ) | ||
| comment = commentfile:read("*a") | ||
| commentfile:close() | ||
| return (comment)</programlisting></para> | ||
| <para>Note that it is necessary to have escape characters surrounding path and filenames.</para> | ||
| <para>The following example demonstrates how to extract exif data from a file:<programlisting> | ||
| --Retrieve the DateTimeDigitized exif tag | ||
| exif_structure = Image:get_exif(); | ||
| DateTimeDigitized = exif_structure:get_datum("Exif.Photo.DateTimeDigitized"); | ||
| return (os.date(DateTimeDigitized)) | ||
| </programlisting></para></section> | ||
| <section id="Warning"><title>Warning | ||
| </title><para>Lua is a powerful programming language. Errors in script files, besides having undesirable side-effects, may cause Geeqie to crash.</para></section> | ||
| </section> |