I use Keynote a lot but the file sizes can sometimes get quite large (100+ MB).
For some of my presentations, this is because images I have added in are larger than expected and Keynote stores them without much if any optimization, sometimes storing large PNG images as TIFF files. tinypng can reduce the size of these larger files without reducing image quality.
You can overwrite a file with:
tinypng mykey.key
You can also output a new file if you want to preserve the original file:
tinypng mykey.key -o mynewkey.key
You may also compress PNG files in the presentation using the Pillow quality scale from 0-100:
tinypng mykey.key -o mynewkey.key --optimize 90
Note that unless you place this executable on your PATH you must run ./tinyping (if using tinypng from the directory you keep it in) or the full path to the tinypng executable. If you have issues running as an executable, you may also use python tinypng.
You must have python 2.7+ or python 3.2+ installed.
You must have the Pillow package installed. Please run:
pip install -r requirements.txt
or
pip install Pillow
Note that tinypng will only reduce the size of your file if the cause is large images. For some of my large presentations this makes a huge difference (300MB -> 30 MB, for example), but your mileage may vary.
Keynote also has File > Advanced > Reduce File Size (as well as other alternatives) that might also be of use to you. However, this performs PNG -> JPEG conversion which doesn't play nicely with text-heavy images.
It is easy to compress lots of files on command line using tinypng:
for file in *.key; do tinypng $file; done
With a bit of bash programming you can also output to new files, run in background, etc.