Fonts and DPI

Making nice looking fonts on your screen takes a little bit on know how. I found out recently that the settings for my fonts were wrong this entire time. And I don’t mean wrong as in pull out the ugly stick wrong, they just needed some personal attention. The best best to improve the fonts is to learn the correct DPI of the screen. This was my problem. I had been using the original DPI the X server choose sine I installed Gnome and I wasn’t sure that it was a good idea to change it. The DPI could be listed in PC handbook that came with the computer which is the best place to look. It, however, isn’t very difficult to figure this out one’s self.

Since most specifications now just list the diagonal length of the screen, I’m gonna use that. The MacBook I uses a 13.3″ (diagonal) LCD screen with 1280 x 800 resolution. I used the Pythagorean Theorem here to correspond the diagonal and horizontal/vertical measurements. 1280² x 800² = c² So the measurement on my MacBook diagonally in pixels is 1509.436… Now figuring your dots per inch is simple, just divide this value by the actual size of the screen diagonally. 1509/13.3. So the DPI of my LCD is 113.49… This is the value to set in Gnomes Font Preferences. Of course, this now means you’ll have to enter all new sizes for the fonts. To make this even simpler by using a function for bc (command line calculator):

echo 'scale=5;sqrt(1200^2+800^2)/12.1' | bc

Xserver and xdpyinfo can also discover the dots per inch. Careful though as the value may not always be correct. Xserver will default to 75×75 if it cannot discover a value.

To discovered these values:

xdpyinfo | grep resolution
cat /var/log/Xorg.0.log | grep DPI

When the fonts are set its best to use whole numbers and partial ones may crunch the fonts (i.e. not show them proportionally).

Thanks to Padaa for showing me that my fonts weren’t up snuff, though I berated him for getting off topic .

• Font Rendering at Gentoo Effects
• DPI Info