From: Alan Braslau <alan.braslau@cea.fr>
To: Cesar Romani <cesar.romani@gmail.com>
Cc: mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: Re: rotating some pages of a pdf
Date: Fri, 6 Jan 2017 08:31:32 -0700 [thread overview]
Message-ID: <20170106083132.6a451a8f@zoo.hsd1.co.comcast.net> (raw)
In-Reply-To: <o4n7gc$2jm$1@blaine.gmane.org>
On Thu, 5 Jan 2017 23:47:00 -0500
Cesar Romani <cesar.romani@gmail.com> wrote:
> The quality of the rotated pdfs, which are images, drops off a little.
> For example, some characters are not so sharp as in the original pdf.
>
> If I use GraphicsMagick I would remedy this with the parameter
> -density as in:
> gm convert -density 300x300 original.pdf -rotate 45 rotated.pdf
From the web:
"A PDF file does not have a density anyway. IM will apply a default
interpretation of 72dpi unless you override it (e.g. -density 300x300
-units pixelsperinch)."
Testing:
convert original.tif -rotate 45 rotated.png
keeps the original density.
1) original.tif was 6000x6000; rotated.png is 8488x8488 (2400dpi)
2) converting to rotated.tif fails
convert: TIFF: negative image positions unsupported rotated.tif @ error/tiff.c/WriteTIFFImage/3609.
3) converting to rotated.pdf does produce a much reduced resolution image.
Indeed, PDF is container, not the best format for manipulating bitmap images.
I take two approaches to this:
1) I manipulate/modify the images explicitly "upstream" before including them in ConTeXt,
using any of my favorite tools; or
2) I manipulate/modify the images using MetaPost, within ConTeXt.
This gives very satisfactory results and does not rely on ImageMagik.
Alan
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prev parent reply other threads:[~2017-01-06 15:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-04 20:31 Cesar Romani
2017-01-04 21:50 ` Hans Hagen
2017-01-04 23:34 ` Cesar Romani
2017-01-05 9:14 ` Hans Hagen
2017-01-06 4:47 ` Cesar Romani
2017-01-06 11:02 ` luigi scarso
2017-01-06 15:31 ` Alan Braslau [this message]
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