From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: David Kastrup Newsgroups: gmane.emacs.devel Subject: Re: Image rescaling Date: Mon, 15 Sep 2014 17:13:53 +0200 Organization: Organization?!? Message-ID: <87egvcrk5q.fsf@fencepost.gnu.org> References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1410794155 16047 80.91.229.3 (15 Sep 2014 15:15:55 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 15 Sep 2014 15:15:55 +0000 (UTC) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Sep 15 17:15:50 2014 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XTY0G-0003YE-8X for ged-emacs-devel@m.gmane.org; Mon, 15 Sep 2014 17:15:44 +0200 Original-Received: from localhost ([::1]:60582 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTY0F-0001pd-Ri for ged-emacs-devel@m.gmane.org; Mon, 15 Sep 2014 11:15:43 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:55069) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTXyl-0007gF-M4 for emacs-devel@gnu.org; Mon, 15 Sep 2014 11:14:16 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XTXyg-0002h2-5L for emacs-devel@gnu.org; Mon, 15 Sep 2014 11:14:11 -0400 Original-Received: from plane.gmane.org ([80.91.229.3]:60113) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XTXyf-0002gp-UJ for emacs-devel@gnu.org; Mon, 15 Sep 2014 11:14:06 -0400 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1XTXye-0002tf-T3 for emacs-devel@gnu.org; Mon, 15 Sep 2014 17:14:04 +0200 Original-Received: from x2f48988.dyn.telefonica.de ([2.244.137.136]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Sep 2014 17:14:04 +0200 Original-Received: from dak by x2f48988.dyn.telefonica.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Sep 2014 17:14:04 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 23 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: x2f48988.dyn.telefonica.de X-Face: 2FEFf>]>q>2iw=B6, xrUubRI>pR&Ml9=ao@P@i)L:\urd*t9M~y1^:+Y]'C0~{mAl`oQuAl \!3KEIp?*w`|bL5qr,H)LFO6Q=qx~iH4DN; i"; /yuIsqbLLCh/!U#X[S~(5eZ41to5f%E@'ELIi$t^ Vc\LWP@J5p^rst0+('>Er0=^1{]M9!p?&:\z]|;&=NP3AhB!B_bi^]Pfkw User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) Cancel-Lock: sha1:bsWqHI9krH4ZNiWPogpwnzUaYpU= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:174328 Archived-At: Stefan Monnier writes: >> Rescaling is apparently a pretty tricky thing that is mostly implemented >> wrong: > >> http://www.4p8.com/eric.brasseur/gamma.html > > Rescaling an image is exactly the same problem as resampling an audio > file (e.g. to play it at 48KHz instead of the 44.1KHz used on the CD > from which it came). > > Doing it naively works, but in some cases gives very poor > results, indeed. Nice meditation but not related to the referenced article. The article is concerned about non-linear quantization. That's "exactly the same problem" as using a good 48kHz to 44.1kHz resampling algorithm on uLaw-quantized audio data rather than linearly-quantized data. Entirely different problem to mess up on. -- David Kastrup