Hi, I'm writing a piece of software that (among other things) displays sheet music (fragments). I've been looking at existing components to take care of rendering the music, and even though lilypond focuses on print rather than on-screen viewing, it seems like a powerful option.
I've long been using lilypond for printed sheets (great product! thanks!), but now started noticing the output looks rather inconsistent on-screen. This is particularly clear when looking at stems and staff lines: some are thin/clear, some are thicker/blurred. Looking to the archives the typical response when this issue is brought up is 'it looks good on paper, probably something in your pdf viewer, don't worry about it'. I'd like to explore how to make the on-screen output look good :). The slim/thick lines are, I suppose, caused by aliasing done by the ps viewer: after scaling it turns out there should be a line at 'pixel 16' (causing a neat clear line at pixel 16) but also one at 'pixel 25,4', causing a blurred line over pixels 25 and 26). For on-screen purposes, it'd be nice to produce output that is 'snapped' to a whole-pixel grid. In case of postscript output, however, this is not possible, as we cannot predict the scaling factor: ps viewers my decide on a scaling factor by looking at things like the current screen resolution and physical size, and it doesn't seem elegant to have lilypond take such parameters in account. So I decided to look at the PNG output. Turns out for png output, lilypond first generates intermediate ps code, then uses gs to turn this into png. Example PNG output at: http://arnout.engelen.eu/files/dev/linuxmusicians/lilypond/postprocessing/test.png Notice how the staff lines of the first staff are clearer than the staff lines of the second staff, and how the stems of the first 2 notes are thicker than the ones of the second 2 notes. Luckily, gs in this case doesn't depend on things like screen size, but specifies a fixed resolution of '101', which (by experimentation, as I couldn't find any specifications) appears to mean '101 pixels per 72 postscript points'. This suggests PNG output could be made more consistent by snapping locations to a coarse whole-pixel grid. To test this, I wrote a simple perl script which takes the intermediate .ps file and modifies each 'moveto' to move to points which are a whole number of pixels apart. http://arnout.engelen.eu/files/dev/linuxmusicians/lilypond/postprocessing/postproc.pl Output shows the lines are now indeed much more consistent, however of course new 'off-by-a-pixel' problems are introduced. Example PNG output at: http://arnout.engelen.eu/files/dev/linuxmusicians/lilypond/postprocessing/processed.png Do you have any ideas for improving low-resolution output? My script is of course just a proof of concept - what would be the 'right' way and place to tackle this? Kind regards, Arnout _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org http://lists.gnu.org/mailman/listinfo/lilypond-user
