[docs] Reduce size of PNG files

[DimitriPapadopoulos]

Subject: smaller PNG files

Feature or Bugfix

• Refactoring

Purpose

• Load faster, less network traffic.

Detail

• Run optipng -o9 on screen captures in the Lumache tutorial.

[chrisjsewell]

Thanks, out of interest, do you have a comparison of the before/after size?

[picnixz]

Thanks, out of interest, do you have a comparison of the before/after size?

GitHub is showing it if you go to files!

[DimitriPapadopoulos]

Indeed, size is reduced to approximately 77 % of the original size (all files as a whole).

Note that optipng does lossless compression. Other software, such as pngquant, achieve even better compression, at the expense of lossy compression.

[picnixz]

Just wondering but... why not just using JPG? (it may be ugly but it's lighter!)

[chrisjsewell]

GitHub is showing it if you go to files!

Oh yeh oops I missed that 🤦

[DimitriPapadopoulos]

Indeed, JPEG sounds like a better choice for lossy compression.

All images in the documentation are currently PNG files. Perhaps lossy compression and JPEG should be addressed in a different PR - starting with a discussion or issue.

[chrisjsewell]

@picnixz I'm happy to merge this as is, since it is at least an iterative improvement?