6.1.2 Image to font conversion

Once you can see what is in the image, the next step is to prepare the IFI file (see section 6.2 IFI files) corresponding to its characters. Imageto relies completely on the IFI files to describe the image; it makes no attempt at optical character recognition, i.e., guessing what the characters are from their shapes.

You must also decide on a few more aspects of the output font, which you specify with options:

• The design size, which you specify with the `-designsize' option. The default is 10pt. Even if you know the true design size of the original scanned image, you may wish to change it. For example, some of our original specimens were stated to be 30pt, but that resulted in the 10pt size being too small to our (20th-century) eyes. So we specified a design size of 26pt.

• The baselines, which you specify with the `-baselines' option. You can specify the baseline for each image row (the bottom scanline of each image row is numbered zero, with coordinates increasing upward). You can make an adjustment for individual characters in the IFI files, but you save yourself at least some of this hassle by specifying a general baseline for each row.

  For instance, in the example image in 6.1 Imageto usage, it would be best to specify `-baselines=2,0'. The `2' is scanline #5 in that image. The `0' is an arbitrary value for scanline #10, which we will ignore via the IFI file (see section 6.2 IFI files).

  For each character written, the `-print-guidelines' option produces output on the terminal that looks like:

  75 (K) 5/315

  This means that character code 75, whose name in the encoding file is `K', has its bottom row at row 5, and its top row at row 315; i.e., the character has five blank rows above the origin. This is almost certainly wrong (the letter `K' should sit on the typesetting baseline), so we would want to adjust it downwards to 0 via the individual character adjustment (see section 6.2 IFI files).

The final invocation to produce the font might look something like this:

imageto -baselines=121,130,120 -designsize=26 ggmr

The output from this would be `ggmr26.1200gf'.