bootanimations

bootanimation format

zipfile paths

The system selects a boot animation zipfile from the following locations, in order:

/system/media/bootanimation-encrypted.zip (if getprop("vold.decrypt") = '1')
/system/media/bootanimation.zip
/oem/media/bootanimation.zip

zipfile layout

The bootanimation.zip archive file includes:

desc.txt - a text file
part0  \
part1   \  directories full of PNG frames
...     /
partN  /

desc.txt format

The first line defines the general parameters of the animation:

WIDTH HEIGHT FPS

WIDTH: animation width (pixels)
HEIGHT: animation height (pixels)
FPS: frames per second, e.g. 60

It is followed by a number of rows of the form:

TYPE COUNT PAUSE PATH [#RGBHEX CLOCK]

TYPE: a single char indicating what type of animation segment this is:
- p -- this part will play unless interrupted by the end of the boot
- c -- this part will play to completion, no matter what
COUNT: how many times to play the animation, or 0 to loop forever until boot is complete
PAUSE: number of FRAMES to delay after this part ends
PATH: directory in which to find the frames for this part (e.g. part0)
RGBHEX: (OPTIONAL) a background color, specified as #RRGGBB
CLOCK: (OPTIONAL) the y-coordinate at which to draw the current time (for watches)

There is also a special TYPE, $SYSTEM, that loads /system/media/bootanimation.zip and plays that.

loading and playing frames

Each part is scanned and loaded directly from the zip archive. Within a part directory, every file (except trim.txt and audio.wav; see next sections) is expected to be a PNG file that represents one frame in that part (at the specified resolution). For this reason it is important that frames be named sequentially (e.g. part000.png, part001.png, ...) and added to the zip archive in that order.

trim.txt

To save on memory, textures may be trimmed by their background color. trim.txt sequentially lists the trim output for each frame in its directory, so the frames may be properly positioned. Output should be of the form: WxH+X+Y. Example:

713x165+388+914
708x152+388+912
707x139+388+911
649x92+388+910

If the file is not present, each frame is assumed to be the same size as the animation.

audio.wav

Each part may optionally play a wav sample when it starts. To enable this, add a file with the name audio.wav in the part directory.

exiting

The system will end the boot animation (first completing any incomplete or even entirely unplayed parts that are of type c) when the system is finished booting. (This is accomplished by setting the system property service.bootanim.exit to a nonzero string.)

protips

PNG compression

Use zopflipng if you have it, otherwise pngcrush will do. e.g.:

for fn in *.png ; do
    zopflipng -m ${fn}s ${fn}s.new && mv -f ${fn}s.new ${fn}
    # or: pngcrush -q ....
done

Some animations benefit from being reduced to 256 colors:

pngquant --force --ext .png *.png
# alternatively: mogrify -colors 256 anim-tmp/*/*.png

creating the ZIP archive

cd <path-to-pieces>
zip -0qry -i \*.txt \*.png \*.wav @ ../bootanimation.zip *.txt part*

Note that the ZIP archive is not actually compressed! The PNG files are already as compressed as they can reasonably get, and there is unlikely to be any redundancy between files.

source: https://android.googlesource.com/platform/frameworks/base/+/master/cmds/bootanimation/FORMAT.md