I get your points, I am often guilty of forgetting those of us with small screens.
I've spent some frustrating hours trying to get those dots into tables, but it doesn't seem like it can be done. I ended up sacrificing the dots instead to keep the table as text. I suppose a (complicated) compromise would be to use svg.
I really should get that wiki page on image cleansing ready. A few hints re. Gimp:
* Colors->Levels to adjust black/white cutoff points
* Filters->Enhancement->Unsharp to improve clarity of ink/line drawings. A value of 0.2-0.4 is normally the best.
However, for a bunch of images such as yours, manually correcting each one is a pain, so I do a batch operation with Imagemagick instead:
for f in *.png
convert $f -level 25%,90% -unsharp 0.3x0.3+3+0 cleansed/$f
To find the 25%, 90% cutoff points I inspected a couple of the images in Gimp with Colors->Levels first and looked at the histogram.
You can save a few extra bytes by running the images through the pngcrush utility afterwards:
pngcrush -d crushed *.png