From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Image transformations Date: Mon, 24 Jun 2019 23:28:32 -0400 Message-ID: References: <20190613165804.GB11266@breton.holly.idiocy.org> <83d0jhz9za.fsf@gnu.org> <20190613192724.GA11945@breton.holly.idiocy.org> <83zhmlxo6d.fsf@gnu.org> <20190613222626.GA12971@breton.holly.idiocy.org> <83o930y7cl.fsf@gnu.org> <20190615104242.GA13368@breton.holly.idiocy.org> <838su3w0de.fsf@gnu.org> <20190616152259.GA22789@breton.holly.idiocy.org> <83d0jdv68i.fsf@gnu.org> <20190617211332.GA55597@breton.holly.idiocy.org> <83a7e6na26.fsf@gnu.org> <8336jymm0g.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="134430"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Jun 25 05:29:40 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 1hfc9L-000Yob-10 for ged-emacs-devel@m.gmane.org; Tue, 25 Jun 2019 05:29:39 +0200 Original-Received: from localhost ([::1]:56180 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hfc9J-0003CM-ER for ged-emacs-devel@m.gmane.org; Mon, 24 Jun 2019 23:29:37 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:40829) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hfc8f-0003CG-SU for emacs-devel@gnu.org; Mon, 24 Jun 2019 23:28:58 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hfc8e-0008O1-T1 for emacs-devel@gnu.org; Mon, 24 Jun 2019 23:28:57 -0400 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:8899) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hfc8d-0008Kg-67; Mon, 24 Jun 2019 23:28:55 -0400 Original-Received: from pmg1.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 7B7AA100B4D; Mon, 24 Jun 2019 23:28:52 -0400 (EDT) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 2AC531009AF; Mon, 24 Jun 2019 23:28:51 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1561433331; bh=PTmsKPfTnBxq3Q738hHqRbMCgBoEpucrGTXHNmMsJWw=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=avJuu7draEMiJ4QpqGZM7ge/xJFzbWlYFFIwIp6MljfEy6GDKlSMpEjJKzU93orDR f9M4HOz0MYBwzfGDxLGPEsl+TlmFLIZ5vQsKcGB11SpFZImuLqDDUspuJWHFMd2NOb KR3NurW2YA2ecv/RfoXx+zaEAsGNuJl0V/p3Q+cIXJX8pMjA0KbQPZvsZFSkNibZbJ DxNr1p4RWaQ/gqQ5IpesplyF7fpiFe22bTAm/6ymvGtEXEmXBgucTA+jkPc7d4CM/f zJOqYwOxp6ICLIEhy3GDP+bIHopjRFTHT5qYQ7sA3AJQZKUio4gVhheMOgjmm9Iylw zGwY9UmkN8deQ== Original-Received: from pastel (69-196-134-84.dsl.teksavvy.com [69.196.134.84]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id CFACB120C58; Mon, 24 Jun 2019 23:28:50 -0400 (EDT) In-Reply-To: <8336jymm0g.fsf@gnu.org> (Eli Zaretskii's message of "Tue, 25 Jun 2019 05:33:51 +0300") X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 132.204.25.50 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:238130 Archived-At: > I don't think I understand what "display position" means here. Did > you mean coordinates of a pixel? Yes, I meant the coordinate in the display as opposed to coordinates in the original image. > What actually happens AFAIU is that in some cases the matrix describes > how to convert the original image to the transformed image, while in > others it describes how to transform the image space into the > transformed space. That's what I meant to say, yes. >> Also, one of the two matrices can't be computed if the transformation >> turns the 2D image into a line (or a point). > We don't support such transformations. There's no option to "magnify" by a factor 0? >> Compared to the cost of handling the image, inverting a 3x3 matrix >> is probably negligible, tho. > Maybe so, but it still sounds silly to me. Part of the reason for my question above is to figure out if the implementation of the API is likely to have such matrix inversion code internally (since it seems quite possible that sometimes one is preferable and sometimes the other). Stefan