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	Tue, 13 Dec 2016 05:27:32 -0800 (PST)
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From:	"Erich Heinzle (a1039181 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Date:	Tue, 13 Dec 2016 23:57:32 +1030
Message-ID:	<CAHUm0tPyoT=u+i3N6mSjHmP9UMf-xdrjk1+kEP3PbBhVsbeKFQ@mail.gmail.com>
Subject:	[geda-user] A workflow for gEDA PCB font symbol/glyph creation
To:	geda-user <geda-user AT delorie DOT com>
Reply-To:	geda-user AT delorie DOT com

I have had some success in converting graphical depictions of
lettering, i.e. from a simple picture, into gEDA PCB compatible font
glyphs with the following technique.

The pcb-rnd fork is particularly well suited to this task for reasons
which will become apparent

A .ppm format image with the glyphs/characters to be converted into a
stroked font compatible with gEDA PCB needs to be found, and its
dimensions in pixels, X, Y, noted

PCB is then loaded, with the .ppm image selected for background display

./pcb-rnd --bg-image my_desired_symbols.ppm &

the board width and height must then be made a multiple of X and Y, to
provide the correct aspect ratio for the exported symbols.

For simple sans serif fonts, the centreline of the glyph can be
traced, to create a stroked, or centreline defined version of the
font. Once a set of silk lines has been generated for a glyph, they
can be selected, and copied into the paste buffer, being careful to
have the cursor suitably positioned at the lower left hand corner of
the glyph consistently for all glyphs processed, to ensure the
vertical alignment of glyphs is properly preserved in the resulting
font.

The paste buffer can then be converted to an element via the menus.

Having done this, the buffer can then be saved with the "Save buffer
elements to file" menu item.

The same process is repeated for any additional glyphs, choosing a
suitable filename in which to save the element each time.

Having created a set of elements (footprints) with silk lines
depicting the needed glyphs, a new layout can be created in which one
copy of each element is placed, using the "load element to paste
buffer" menu item, and then placing the element.

It is at this point that pcb-rnd can be used to advantage (available
at http://repo.hu/projects/pcb-rnd/ ).

Having placed all of the desired elements on the layout (each element
being a footprint depicting a unique glyph), select all of them, and
copy them to the buffer.

pcb-rnd allows the buffer elements to be saved to file, as a kicad
legacy library of modules.

The library of modules (a .mod file) can then be converted into font
glyph definitions with

https://github.com/erichVK5/KicadModuleToGEDA

by using the -g flag when invoked.

Furthermore, KicadModuleToGEDA allows a magnification ratio to be
specified in the module header, so that the final glyph sizes can be
fine tuned to be around 5000 centimils high, with a descent of around
1000 (i.e the dangly bit of a lower case p or q), and a stroke width
of between 600 and 800 centimils, given the silk screen process
limitations of typical pcb fabs.

This ability to fine tune the magnification during final conversion
eliminates the need for careful scaling in the image preparation and
subsequent drawing phase of the process.

The result will be a set of files, one per glyph, containing glyph
definitions which can be copied and pasted into a font file i.e. like
/src/default_font, replacing existing symbol definitions.

This workflow may save someone a lot of tedious reinvention of the wheel.

There is clearly scope to use a work process like this in pcb +/-
further refinements, to produce engraving fonts relatively quickly and
easily, since tools such as fontforge are designed to work on outline
fonts (i.e. ttf, PS), rather than centreline defined a.k.a. stroked
fonts.

Cheers,

Erich.

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