From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Emanuel Berg Newsgroups: gmane.emacs.help Subject: Re: function to get inverse color name? Date: Thu, 24 Apr 2014 19:51:26 +0200 Organization: Aioe.org NNTP Server Message-ID: <87tx9i4nvl.fsf@nl106-137-194.student.uu.se> References: <2c7e7b5b-73ec-45ae-9bf5-b638aad861ff@googlegroups.com> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1398383629 19193 80.91.229.3 (24 Apr 2014 23:53:49 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 24 Apr 2014 23:53:49 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Fri Apr 25 01:53:44 2014 Return-path: Envelope-to: geh-help-gnu-emacs@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 1WdTSZ-00038J-DY for geh-help-gnu-emacs@m.gmane.org; Fri, 25 Apr 2014 01:53:43 +0200 Original-Received: from localhost ([::1]:45518 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WdTSZ-0001Ns-1f for geh-help-gnu-emacs@m.gmane.org; Thu, 24 Apr 2014 19:53:43 -0400 Original-Path: usenet.stanford.edu!news.tele.dk!news.tele.dk!small.news.tele.dk!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!news.stack.nl!aioe.org!.POSTED!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 43 Original-NNTP-Posting-Host: VVbyYd/iFZoeWNmD9i++cQ.user.speranza.aioe.org Original-X-Complaints-To: abuse@aioe.org User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) X-Notice: Filtered by postfilter v. 0.8.2 Cancel-Lock: sha1:h0QoddSQcmjtccFYjcAQkLxcbBk= Mail-Copies-To: never Original-Xref: usenet.stanford.edu gnu.emacs.help:205092 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:97356 Archived-At: unfrostedpoptart writes: > Does anyone have a function that takes a named color > (e.g. "Red") and returns the inverse? I guess it > would convert the name to RRGGBB, subtract each 8-bit > value from 256, and then convert back to a name. Interesting question! I would start out examining `color-name-to-rgb' - you want the inverse of that, so check out how they did it (in color.el). Try it: (color-name-to-rgb "white") Second, check out color.el in general to see what's there that can help you. Third, if everything fails, check out the output of (list-colors-display) As you see, strings to the left, hex code to the right. You have to match your colors with the right column, and then pick the string to the left. Because you intend to process the color codes, to acquire the inverse, perhaps you will end up with colors that aren't defined. I don't know how that will work out - will it produce an error (on assigning the color), or will Emacs pick "the closest"? If Emacs does that, you can reuse the same function. If not, you'll have to write that yourself as well - linear algebra and vectors in the color cube... Yikes! Doing this manually is an option, of course :) And don't be too sure "the inverse" will actually produce the perceived inverse result. Good luck! And report back what you learn on the way... -- underground experts united: http://user.it.uu.se/~embe8573