Graphics
From XOCPWiki
This page describes the current graphics capability of the application.
Contents |
Scalable Vector Graphics (SVG)
SVG capability for slides is implemented.
SVGZ (compressed SVG) is not yet implemented, but may be useful to further reduce file sizes.
SVG is great for slides that are mostly or all text, due to its excellent scalability and low file size. It is more involved to convert slides to SVG, however. One major issue is the way that embedded bitmap graphics are handled; these should be rescaled to screen resolution and properly compressed to avoid long render times and large file sizes.
SVG is handled by the rsvg library and Cairo on the XO.
Portable Network Graphics (PNG)
PNG is also implemented. There are no known issues with PNG.
PNG slides may take more space than SVG slides, but they are more consistent in their sizes and have consistently short render times (unlike SVGs which can range in complexity and therefore render times.)
PNG works, but is not optimal, for large photographs.
PNG is handled by Cairo on the XO.
JPEG
JPEG is also implemented.
JPEG slides may be an ideal format for most slides. The compression is good (reducing most 1024x768 slides down to around or less than 100 KB is quite possible.) Compression artifacts are not readily obvious on the XO's screen as long as the compression is not too extreme.
JPEGs also seem to render faster than all but the simplest SVG images.
References
- This Cairo Tutorial for Python Programmers is a good introduction and reference about Cairo terminology and performing basic graphic operations on the XO.
- PyGTK 2.0 Reference Manual
