Re: converting 360 pages' pdf file take too much memory

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On Fri, 10 Mar 2017, =E7=8E=8B=E5=8F=AF wrote:

> If I increase image density with overwrited readImages, the memory usag=
e is
> higher.
> Since api read and output each page one by one, why it take so much mem=
ory
> and is there any solution for it?
>
> Another question is, When I run the program, A progress "gs"  runs in
> background and exits after a while, then I can see process of my progra=
m in
> process list.
> I do not understand what 'gs' process is and how it running.

GraphicsMagick always reads all input pages/frames before it proceeds=20
to do anything more.

GraphicsMagick uses Ghostscript ('gs') to render the PDF (or=20
Postscript) into a sequence of raster image files which are then read=20
into GraphicsMagick's internal format.  Someday this may be improved=20
but the Ghostscript license is not conducive to direct linkage between=20
GM and Ghostscript.  Perhaps a different PDF renderer would be used.

There is a way to read just a range of pages by appending a page range=20
to the input file name.  For example

   readImages(&images, "/test/linuxfun.pdf[0-49]");

should read the first 50 pages.  When dealing with large PDFs, you can=20
incrementally read batches of pages from the same file in order to=20
limit resource consumption.  You will know when you reach the end of=20
the PDF due to obtaining fewer pages than requested.

This works better for PDF than for Postscript because PDF is indexed=20
and Postscript is not.

Even with incremental reading, there will still be a resource issue=20
unless your program is able to deal with a subset of pages at a time.

Bob

--=20
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen=
/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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