Documentation/modification of top/bottom margin in eps/pdf/svg hb-view output

[HinTak]

The pixel-based output of hb-view (png and ansi) seems to have 16 as pixels in the margin and can be lowered by --margin. But the eps/pdf (I.e cairo) -based output, it is not exactly clear what 16 means, though I suppose it is in dpi units.

What's troubling is the space above and below - compared to ansi, perhaps?

[HinTak]

I think I have asked this question before, though I don't remember the answer :) . The font I am having a lot of head/bottom room is Lohit Devanagari , if that's important.

[behdad]

But the eps/pdf (I.e cairo) -based output, it is not exactly clear what 16 means, though I suppose it is in dpi units.

It's points (72points=1in).

[behdad]

What's troubling is the space above and below - compared to ansi, perhaps?

The ansi output skips empty lines from top/bottom. The other outputs don't, and respect font's ascent/descent.

[HinTak]

I guess Lohit Devanagari has gigantic ascent/descent. Would be nice to have a "tight bounding" mode like the ansi one for the Cairo based outputs... Anyway, some of these info could go into the --help-... display messages.

[behdad]

This was previous discussion: #79
Feel free to submit PR for doc improvements. Thanks.