From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.comp.tex.context/14009 Path: main.gmane.org!not-for-mail From: Bill McClain Newsgroups: gmane.comp.tex.context Subject: Re: Dithering (off-topic) Date: Tue, 4 Nov 2003 09:48:59 -0600 Sender: ntg-context-admin@ntg.nl Message-ID: <20031104094859.4083dc06.wmcclain@salamander.com> References: <3FA245CC.30502@econ.muni.cz> <20031031063731.12ddf19d.wmcclain@salamander.com> <3FA7AAFE.9070900@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 1067961173 28171 80.91.224.253 (4 Nov 2003 15:52:53 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Tue, 4 Nov 2003 15:52:53 +0000 (UTC) Original-X-From: ntg-context-admin@ntg.nl Tue Nov 04 16:52:51 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 1AH3UB-0002pH-00 for ; Tue, 04 Nov 2003 16:52:51 +0100 Original-Received: from ref.ntg.nl (localhost.localdomain [127.0.0.1]) by ref.ntg.nl (Postfix) with ESMTP id 2E43810AFC; Tue, 4 Nov 2003 16:52:48 +0100 (MET) Original-Received: from hall.mail.mindspring.net (hall.mail.mindspring.net [207.69.200.60]) by ref.ntg.nl (Postfix) with ESMTP id 9080A10ABB for ; Tue, 4 Nov 2003 16:45:17 +0100 (MET) Original-Received: from 0-1pool120-250.nas9.cedar-rapids1.ia.us.da.qwest.net ([67.1.120.250] helo=atipa.local) by hall.mail.mindspring.net with esmtp (Exim 3.33 #1) id 1AH3Ml-0006hs-00 for ntg-context@ntg.nl; Tue, 04 Nov 2003 10:45:11 -0500 Original-Received: from atipa.local (localhost [127.0.0.1]) by atipa.local (Postfix) with SMTP id 3F88232BA0 for ; Tue, 4 Nov 2003 09:48:59 -0600 (CST) Original-To: ntg-context@ntg.nl In-Reply-To: <3FA7AAFE.9070900@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:14009 X-Report-Spam: http://spam.gmane.org/gmane.comp.tex.context:14009 On Tue, 04 Nov 2003 14:34:54 +0100 Michal Kvasnicka wrote: > BTW, is there some easy way to set the size of the dithering points > (eg. 2x2 pixels, 3x3 pixels), or should I do it ex post in some image > editor (Gimp, imagemagick)? I haven't studied the Floyd-Steinberg algorithm, but it seems to be an error-difusion technique that handles that automatically. The resulting pixel dimensions of the image are the same as the original. There are other halftoning methods you can experiment with in pgmtopbm. Although I did some experimentation, I am by no means an expert at this. My method is simply to expand the orginal image to so that a pixel in the image will be a dot on the output. Using the example I posted before, the image was 3.5 inches wide, the printer was 600 dots per inch, so I sized the graphic to 3.5 x 600 = 1950 pixels before halftoning. I've dealt with only one printer so far, but the results have been good. Depending on the original grayscale image, it may need to be normed (pgmnorm) or smoothed (pgmsmooth) before halftoning. -Bill -- Sattre Press Pagan Papers http://sattre-press.com/ by Kenneth Grahame info@sattre-press.com http://pp.sattre-press.com/