Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!uakari.primate.wisc.edu!dali.cs.montana.edu!milton!wiml From: wiml@milton.u.washington.edu (William Lewis) Newsgroups: comp.lang.postscript Subject: Re: What does concat do? Message-ID: <13313@milton.u.washington.edu> Date: 20 Dec 90 04:57:56 GMT References: Organization: University of Washington, Seattle Lines: 31 I'm not exactly a PS wizard, but I'll take a stab at this. The 'concat' operator modifies the current coordinate system. It's a generalization of translate, scale, and rotate... basically, it takes a 6-element array, [a b c d e f], converts it into the matrix [a c 0] [b d 0] [e f 1] (I may have the upper left corner transposed). Anyway, it then replaces the current coordinate transformation matrix (which is what specifies the correspondence between 'points' and device pixels) withe the old CTM multiplied by this matrix. For instance, [1 0 0 1 15 37] concat has the same effect as 15 37 translate ... I think. (In effect, adding 15 to every X coordinate and 37 to every Y coordinate given from then on.) I'm not sure why a paint program would be changing its coordinate system before every line it draws, but who can fathom machine-generated code? -- wiml@milton.acs.washington.edu Seattle, Washington (William Lewis) | 47 41' 15" N 122 42' 58" W "These 2 cents will cost the net thousands upon thousands of dollars to send everywhere. Are you sure you want to do this?"