Pixel font/character filters

[Ai]

I've recently been exploring the design space of pixel fonts and compiling some reference sheets.
This one is about filters suitable for use in helping create variants of pixel fonts:


(intended viewing zoom : 200 - 400%; Palette is the excellent Solarized)

The easiest way to try them out is via GIMP (2.8+) and the GMIC plugin for GIMP (packaged separately). At least some of them are available in other software (eg. GrafX2).

Overall, morphological operations (dilate, erode, opening, closing) are heavily emphasized. Value Propagate is especially high.. value, since it allows you to limit the direction of propagation of the erode or dilate operations, which allows you to thin or thicken vertical or horizontal strokes independently (cf. the 'military' variant done by thinning horizontal strokes)

I tried to be pretty exhaustive in searching for relevant filters, but if you have another filter that's relevant, I'm happy to update the sheet.

[Ai]

I guess I was thinking this was obvious, but in retrospect, I'll point out that all of these can be applied to partial selections, which can be useful when applied to a subset of columns or rows:


(done by selecting bottom half of each character, and applying GMIC Morphological-> Dilation - Original (Octagonal))

Maybe I should also explicitly explain that the abbreviations sq, circ, and oct refer to square, circular, and octagonal 'kernel shapes' for morphological operators. The kernel shapes effect exactly which pixels are affected by the morphological operator; for example,
at size 2, Octagon is the most suitable for applying an 'outline effect' via "Dilation - Original". This is because at size 2, it forms a diamond that perfectly 'borders' the central pixel.

This image illustrates the difference. The original pixel is marked in pink and affected pixels are marked in blue.