Update March 4, 2015 (1.1): Add experimental unicode generation and made errors more descriptive. Not all fonts support all the unicode characters, so this setting is not recommended.
Recently, I figured out how to create dynamic images in Java, so I felt like I should create a font generator from it, and now here I am writing this blog post.
This tool creates HD font resource packs using installed fonts on the system. If it's supported and installed in your computer, you can use it.
To use, select the font and texture size from the dropdown boxes and click Create. A zip named using the font name and the size will be created in the directory it was started from. Add this file as a resource pack.
For command line usage, just give it a font name with spaces replaced with underscores, then the texture size, one of [32, 64, 128, 256, 512]. A nonexistent font will use the JRE default (Dialog.plain).
Download [1.2] (Requires Oracle Java 7, not OpenJDK)
Pregenerated x32 Fonts (Agency, Arial Rounded, Arial, Comic Sans, Courier New, Impact, Tahoma, Times New Roman, Verdana) (Generated with v1.0)
Note: Every font is different, so some may look weird and require tweaking after generation, but most fonts should be fine.