-danti-alias-factor looks great - thanks for the suggestion - but I believe it won't work for (extremely) large, transparent images... Unless Ghostscript is called with the option
-dMaxBitmap=2147483647 (or similar) from within LilyPond. The reason is that without that option set, Ghostscript will revert to the png16m device (rather than the pngalpha device) for extremely large images, presumably because of memory reasons... and with png16m instead of pngalpha I will loose the transparency, which I don't want to...
PS: Pasting the previous discussion regarding GS / pngalpha / png16m for reference.
------------
Regarding how to create large, transparent scores:
When the images you output are reasonably small, 'lilypond... --png ... -dpixmap-format=pngalpha ....' successfully generates the transparent images. Once the images surpass a certain size however, transparency seems to fail, and the .png images come out with a white background.
If you run the following lilypond command: 'lilypond --png -dresolution=100 -dpixmap-format=pngalpha --ps --verbose
x.ly'
and look at the bottom of the log, you can see the actual Ghostscript command called by Lilypond used to create the .png. It is going to look something like this:
gs -dDEVICEWIDTHPOINTS=37533.99 -dDEVICEHEIGHTPOINTS=2160.00 -dGraphicsAlphaBits=4 -dTextAlphaBits=4 -dNOPAUSE -sDEVICE=pngalpha -sOutputFile="./x.png" -r100 "
x.ps" -c quit
As you can see it is correctly using the device 'pngalpha' in order to generate the transparent image. The problem seems to be that - upon inspecting the logs - Ghostscript reverts to the device png16m instead, which is unable to generate a transparent image.
The way to fix this is to tweak the memory usage options for Ghostscript, specifically by adding the option '-dMaxBitmap=
2147483647' to the Ghostscript command, as in the following snippet:
gs -dDEVICEWIDTHPOINTS=37533.99 -dDEVICEHEIGHTPOINTS=2160.00 -dMaxBitmap=
2147483647 -dGraphicsAlphaBits=4 -dTextAlphaBits=4 -dNOPAUSE -sDEVICE=pngalpha -sOutputFile="./x.png" -r100 "
x.ps" -c quit
This allocates more memory to Ghostscript and makes it correctly use the pngalpha device, and thus correctly output a transparent image. If you have a 64 bit machine perhaps you can extend it further. It should also be possible to rebuild lilypond from source and compile it with this option baked in, but I haven't tried that....
Perhaps this information helps someone trying to create large, transparent images in LilyPond!
On Fri, Feb 14, 2014 at 1:38 AM, David Kastrup
<address@hidden> wrote:
Erik Linde <
address@hidden> writes:
> Hey Chris / David,
>
> Adding the --png option when you run your lilypond command works fine (as
> David stated)... Also, you may want to set the -dresolution parameter to
> something high like 300 (DPI) to get a good resolution. Or even set it to
> 600, and then shrink it to 300DPI using some image processing software such
> as Photoshop or ImageMagick / GraphicMagick to achieve an even better
> anti-aliasing effect.
-danti-alias-factor=2 option?
--
David Kastrup