Another embold method for rending PDF

[caritas]

To enhance readability of PDF file on e-ink reader, the glyph (font) need to be embolded. Current available embold method is something as follow:

1. Enlarge image
2. dilate ink
3. Scale image to original size

Now, I find another method to embold font in glyph granularity via using:

FT_GlyphSlot_Embolden() of libfreetype

A patch for libpoppler is attached. I think this method can provide acceptable effect with better performance, because the embold only need to be done once for each glyph. So this may can be used in software in e-ink devices.

The rending effect is attached too:

chap6.pdf: sample pdf file
org.png: original rending method, without embolding
embold.png: embolded with this method
pl.png: embolded with pdf2lrf.