Re: Lots of temporary files when generating png files

[Aaron Hill]

On 2020-02-04 7:59 am, Anthony Rushforth wrote:
> @Aaron : Because if I use your command line I get this png : a full 
> page
>
> I want a cropped png, and I found the command line I use in the
> documentation (
> http://lilypond.org/doc/v2.19/Documentation/usage-big-page#lilypond-output-in-other-programs)
> :
>
> > To produce ‘PNG’ images;
> >
> > lilypond -dbackend=eps -dno-gs-load-fonts -dinclude-eps-fonts --png 
> > myfile.ly
> I don't understand why it has to be "eps", but it's the only way I 
> found...
> do you have another option to get cropped images ?

Two options: (1) fix your \paper settings, or (2) use the crop feature 
of LilyPond.

Regarding the first option, the idea is to set up your \paper properly 
so that the output from LilyPond is what you want.  My use case involves 
outputting transparent PNGs for use in projection.  I have my paper size 
configured to match the slides, and I have adjusted staff and font sizes 
accordingly to try to maintain good readability.  In this way, the 
output from LilyPond is nearly perfect for dropping into a presentation. 
 I only need to use ImageMagick for a little post-processing, which does 
include cropping transparent pixels, since some slides are not as "full" 
as others.  For reference, here is an excerpt from my build script 
showing the IM command-line:

####
./imagemagick/magick convert $file -trim +repage \
  -filter Spline -define filter:blur=0.707 \
  -distort Resize 50% -density 56.69 PNG32:$file
####


Regarding the second option, LilyPond provides a built-in form of 
cropping.  The amended command-line would look as follows:

####
lilypond \
  -dcrop -dno-print-pages \
  -dresolution=288 \
  -dpixmap-format=pngalpha \
  --png \
  source.ly
####

Note that -dno-print-pages is used to suppress the normal output.

I went the IM route because -dcrop does change how LilyPond handles 
vertical spacing.  Depending on your needs, you might find -dcrop works 
well enough.


-- Aaron Hill

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