From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Alan Third Newsgroups: gmane.emacs.devel Subject: Re: Image transformations Date: Wed, 12 Jun 2019 23:15:32 +0100 Message-ID: <20190612221532.GA11110@breton.holly.idiocy.org> References: <9A21DE14-BB5F-426E-BBB2-19C87930E733@gnu.org> <20190611200233.GA80199@breton.holly.idiocy.org> <83imta95z0.fsf@gnu.org> <20190612220746.GA89208@breton.holly.idiocy.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="42663"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mutt/1.12.0 (2019-05-25) Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Jun 13 01:01:38 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hbCFL-000Aya-3x for ged-emacs-devel@m.gmane.org; Thu, 13 Jun 2019 01:01:35 +0200 Original-Received: from localhost ([::1]:35836 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hbCFH-0006Rb-TL for ged-emacs-devel@m.gmane.org; Wed, 12 Jun 2019 19:01:33 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:49925) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hbBkq-0007k2-TD for emacs-devel@gnu.org; Wed, 12 Jun 2019 18:30:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hbBXA-0002QV-NC for emacs-devel@gnu.org; Wed, 12 Jun 2019 18:15:58 -0400 Original-Received: from mail-wm1-x32e.google.com ([2a00:1450:4864:20::32e]:37639) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hbBX4-0002EI-8l; Wed, 12 Jun 2019 18:15:50 -0400 Original-Received: by mail-wm1-x32e.google.com with SMTP id 22so8064129wmg.2; Wed, 12 Jun 2019 15:15:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=W2CqBDk68Q4HiO/A9gIx11SdkgKg4MizOsUDS1GmeZA=; b=hNyOcH4gz/8slbURRzFSPEI0mf4+eebN7wS4PQLAIlv9H+J3bNeT5amJPF6Ok5BYJW /VR6luiHSSmkP4RmbmhwY7n9qKhSxDrW+b7G+SlLQWUb5c6ozcaTADWgel82omMz8jS3 D7cP+/FK7grIjRGt9iyIeA8RI1f1QTsgK3MalACjF81IPPiqlOeBpZ3OtbM27rZzLn8i ek608rbiIZ5t/o7xCqlvSGHs2suVpKIzgYPFV6vWZQKr4MWo+6AvrMValqNOrwEOF34k /CrB30FMikY2ib7cPNynplpPYn8gFy4ApitipBY92fKnhgdIBdQnxEfYwVYTNKLksTwZ VhEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition :content-transfer-encoding:in-reply-to:user-agent; bh=W2CqBDk68Q4HiO/A9gIx11SdkgKg4MizOsUDS1GmeZA=; b=IRTxqYBVwbLXuG9WHMvlolf76LutL3trA0paZSSpYTbXcB8YU8VBorhFmqRlYMZLTz RN2i8vE0u6g14cX6rdQ+VE5cX5rz+R6nc/HZIk4bPVAIBhoeQ0D5IgbraedYyp++skG+ XjGjLGYsmWuME6NtWzW74XDQjWQsWOqn+J0PluCaQtGwdAhW0qkMMNrSej6h8LEYRdbS dDNncjTIsV6wHzVb8/P/Tta8zLmv6I19WDxIaft8HQgmp2Xlgv3RSzDPj6tQgCMYytyA yxmpaDtF99OOWRZ24BDeEZsJ/bPa6/wPGGtYaad+EtbqVDOsWnJDdd9u3cq8bbmEAnAz McJQ== X-Gm-Message-State: APjAAAVF5mFrXIVhIXlFkMoKzLU6J2AcwbuyHCFYom3oSx2WkBiCbaor XM6ODpPABxyuYHymmAD5fULYeHw9 X-Google-Smtp-Source: APXvYqxe2635yCPyvmSzwyPR1HPGqCVq3Uz7LMTKBgVdltLMDwyuRjzTq+BPQnWeeIY1EJFfJQQQTQ== X-Received: by 2002:a1c:a648:: with SMTP id p69mr860714wme.155.1560377735199; Wed, 12 Jun 2019 15:15:35 -0700 (PDT) Original-Received: from breton.holly.idiocy.org (ip6-2001-08b0-03f8-8129-0518-5a78-4fbd-d772.holly.idiocy.org. [2001:8b0:3f8:8129:518:5a78:4fbd:d772]) by smtp.gmail.com with ESMTPSA id s10sm1451247wmf.8.2019.06.12.15.15.34 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 12 Jun 2019 15:15:34 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20190612220746.GA89208@breton.holly.idiocy.org> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:4864:20::32e X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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" Xref: news.gmane.org gmane.emacs.devel:237467 Archived-At: On Wed, Jun 12, 2019 at 11:07:46PM +0100, Alan Third wrote: > > > + tx and ty represent translations, m11 and m22 represent scaling > > > + transforms and m21 and m12 represent shear transforms. Having written a huge tract and messed around with outputting various transform matrices, it seems clear to me now that the above is not quite as straightforward as I was thinking. A 90 degree rotation followed by a resize doesn’t actually put anything in m11 and m22, so clearly m11, m12, m21 and m22 interact in mysterious ways. My feeble excuse is that I’m not a mathematician. -- Alan Third