Re: Cropped output (à la -dpreview) possible in Fin ale and Sibelius

[Carl Peterson]

On Tue, Apr 9, 2013 at 4:45 PM, David Kastrup <address@hidden> wrote:

Carl Peterson <address@hidden> writes:

> I'm not an expert on GhostScript, but in practice it is nearly always
> best to rasterize vector graphics at the intended output resolution.

Except when it isn't.  What makes you think that the PDF viewers are
doing anything but rasterizing vector graphics at the intended output
resolution?

Even though a PDF viewer is rasterizing at the output resolution, it isn't rasterizing at the intended resolution of the PDF file. The basic Lilypond output is intended for output at print resolution (say, 300dpi or higher). We know this is a factor because Lilypond already uses multiple versions of the engraving fonts so that smaller and larger scores are equally "beautiful music."

PDF viewers cannot discern rendering intent. When a generic PDF viewer looks at Lilypond output, it doesn't know that the stems need to be treated as lines and not rounded rectangles below a certain resolution, or that it needs to render all the staff lines even if one of the staff lines "disappears" at that resolution. Lilypond knows what a stem is and what a staff line is and if it's producing its own PNG output, it can make sure those elements get rendered properly for the intended resolution.

Vectors can be scaled up with out limit and preserve image quality, but in a raster environment (like a computer screen), they cannot be scaled down without limit with the same expectation.

Carl