Lossless compression of scaled images

[chrisgherbert]

Losslessly compressed the scaled versions of the images. This reduced the file size by more than 10% but should not affect image quality. A nice side effect is that sites using these images should have a significantly higher Google Page Speed score.

[hugovk]

@chrisgherbert Sounds good.

How did you compress them? Is it something that can be added to resize-photos.sh, so future additions are also compressed?

[chrisgherbert]

I used a GUI tool, ImageOptim, but behind the scenes I think it uses JPEGOptim (https://github.com/tjko/jpegoptim).

I could add that to the script, though I don't know if you want another dependency in addition to ImageMagick.

[hugovk]

Yes please, do add it to the script, another dependency's fine. I guess if the program's not available, the other conversions will still take place.

In the meantime I'll merge this one.

Thanks!