I was curious if it would be possible to have the images under the core framework optimized with lossless compression tools which should give show no visible difference to users. I ran two open source tools for compression and here are my findings.
Extjs Images Directory located under resources
Without compression 1.46MB (1,538,315 bytes)
With pngopt ran on files 1.44 MB (1,513,226 bytes)
saving a total of 25 kb (64% decrease)
With pngopt ran on files 1.44 MB (1,513,226 bytes)
with pngopt and gifopt 423 KB (433,942 bytes)
saving a total of 1053 kb (77% decrease)
For a total savings of 1079 kb (141% decrease)
with only lossless compression.
I enclosed a zip file with all the needed tools and images directory for the 4.0.7 release compressed and uncompressed for comparision.
The zip files are 7 zip format and not normal zip so the you will need 7 zip and the file extension will need changed to 7z