From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.comp.tex.context/13989 Path: main.gmane.org!not-for-mail From: Bill McClain Newsgroups: gmane.comp.tex.context Subject: Re: Dithering (off-topic) Date: Fri, 31 Oct 2003 06:37:31 -0600 Sender: ntg-context-admin@ntg.nl Message-ID: <20031031063731.12ddf19d.wmcclain@salamander.com> References: <3FA245CC.30502@econ.muni.cz> Reply-To: ntg-context@ntg.nl NNTP-Posting-Host: deer.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Trace: sea.gmane.org 1067604088 20225 80.91.224.253 (31 Oct 2003 12:41:28 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Fri, 31 Oct 2003 12:41:28 +0000 (UTC) Original-X-From: ntg-context-admin@ntg.nl Fri Oct 31 13:41:26 2003 Return-path: Original-Received: from ref.vet.uu.nl ([131.211.172.13] helo=ref.ntg.nl) by deer.gmane.org with esmtp (Exim 3.35 #1 (Debian)) id 1AFYak-0000BU-00 for ; Fri, 31 Oct 2003 13:41:26 +0100 Original-Received: from ref.ntg.nl (localhost.localdomain [127.0.0.1]) by ref.ntg.nl (Postfix) with ESMTP id 60A2B10B2B; Fri, 31 Oct 2003 13:41:22 +0100 (MET) Original-Received: from maynard.mail.mindspring.net (maynard.mail.mindspring.net [207.69.200.243]) by ref.ntg.nl (Postfix) with ESMTP id E4D9110B1D for ; Fri, 31 Oct 2003 13:33:42 +0100 (MET) Original-Received: from 0-1pool120-89.nas9.cedar-rapids1.ia.us.da.qwest.net ([67.1.120.89] helo=atipa.local) by maynard.mail.mindspring.net with esmtp (Exim 3.33 #1) id 1AFYT9-0000XO-00 for ntg-context@ntg.nl; Fri, 31 Oct 2003 07:33:36 -0500 Original-Received: from atipa.local (localhost [127.0.0.1]) by atipa.local (Postfix) with SMTP id BCA412A125 for ; Fri, 31 Oct 2003 06:37:31 -0600 (CST) Original-To: ntg-context@ntg.nl In-Reply-To: <3FA245CC.30502@econ.muni.cz> X-Mailer: Sylpheed version 0.9.5claws (GTK+ 1.2.10; i686-suse-linux) Errors-To: ntg-context-admin@ntg.nl X-BeenThere: ntg-context@ntg.nl X-Mailman-Version: 2.0.13 Precedence: bulk List-Help: List-Post: List-Subscribe: , List-Id: mailing list for ConTeXt users List-Unsubscribe: , List-Archive: Xref: main.gmane.org gmane.comp.tex.context:13989 X-Report-Spam: http://spam.gmane.org/gmane.comp.tex.context:13989 On Fri, 31 Oct 2003 12:21:48 +0100 Michal Kvasnicka wrote: > I typeset a church bulleting. It is printed on a laserjet printer (600 > > dpi), and then copied on a copy machine. As for letters, all is right. > > But figures (photos) are this way spoiled. I guess it would help > either to force PDF to print the figures in some very low resolution > (150 dpi), or (probably better) to dither the figures and include them > in PNG (instead of ordinary JPEG). Can some of you tell me how to do > it? I tried ImageMagick's convert to dither the photos, but outcomes > were really poor. Is there some good free software for this (in the > best case in Linux)? Or can I do it some way in PDF? I suspect you need to halftone the photos before including them. All the gray pixels must be converted into a pattern of black and white equivalents. On Linux you have the netpbm package which has everything you need. The specific utility is pgmtopbm with various switches. There are other utilities for converting to and from the netpbm file formats. Here is an example of a pipeline I use to do several manipulations at once: pnmscale -width=1950 pleiades.pnm | pnmsmooth -size 5 5 | pgmtopbm -fs -value 0.5 | pnmtopng > pleiades.png pnmscale: expand to a known size pnmsmooth: try to obscure the halftone of the original photo pgmtopbm: apply new halftone, -fs = "floyd-steinberg" halftoning pnmtopng: convert to png for inclusion into pdf The trouble with halftone images is that they are not resolution-independent. You may have to adjust the image size and parameters depending on your printer. Also, halftoned images do not display well in some graphics programs, although acroread does a pretty good job when they are included in pdf files. -Bill -- Sattre Press The King in Yellow http://sattre-press.com/ by Robert W. Chambers info@sattre-press.com http://kiy.sattre-press.com/