font-patcher: Preserve existing bitmaps

[why]
Bitmaps existing in a font are discarded. The font-patcher script just
cares about outline fonts.

[how]
If the sourcefont has bitmaps, do save them into the patched font. Note
that this does not generate bitmaps for the patched-in glyphs (icons).

[note]
Fonts probably affected in src/unpatched-fonts:
    bitmap (11,) (gohufont-11)
    bitmap (14,) (gohufont-14)
    bitmap (11,) (gohufont-uni-11)
    bitmap (14,) (gohufont-uni-14)
    bitmap (7, 9, 10, 12, 14, 18, 24) (ProFontIIx)
    bitmap (12, 14, 16, 18, 20, 22, 24, 28, 32) (TerminusTTF-Bold Italic-4.40.1)
    bitmap (12, 14, 16, 18, 20, 22, 24, 28, 32) (TerminusTTF-Bold-4.40.1)
    bitmap (12, 14, 16, 18, 20, 22, 24, 28, 32) (TerminusTTF-Italic-4.40.1)
    bitmap (12, 14, 16, 18, 20, 22, 24, 28, 32) (TerminusTTF-4.40.1)

Fixes: ryanoasis#86

Reported-by: DoctorKnowsBetter
Signed-off-by: Fini Jastrow <[email protected]>

font-patcher

@@ -271,7 +271,11 @@ class font_patcher:
                 fontname = sourceFont.cidfontname
             outfile = os.path.normpath(os.path.join(self.args.outputdir, fontname + self.args.extension))
             # the `PfEd-comments` flag is required for Fontforge to save '.comment' and '.fontlog'.
-            sourceFont.generate(outfile, flags=(str('opentype'), str('PfEd-comments')))
+            bitmaps = str()
+            if len(self.sourceFont.bitmapSizes):
+                print("Preserving bitmaps {}".format(self.sourceFont.bitmapSizes))
+                bitmaps = str('otf') # otf/ttf, both is bf_ttf
+            sourceFont.generate(outfile, bitmap_type=bitmaps, flags=(str('opentype'), str('PfEd-comments')))
             message = "\nGenerated: {} in '{}'".format(self.sourceFont.fullname, outfile)
 
         # Adjust flags that can not be changed via fontforge