>From poynton@poynton.com Tue Jan 31 23:54 EST 1995 Date: Tue, 31 Jan 1995 23:55:55 -0500 From: poynton@poynton.com (Charles Poynton) To: MIKE.NELSON%MSFC26PO@x400gw.msfc.nasa.gov (Michael A. Nelson), framers@uunet.uu.net Subject: Re: HELP! Need good screen capture for users guides! Newsgroups: comp.text.frame In article , MIKE.NELSON%MSFC26PO@x400gw.msfc.nasa.gov (Michael A. Nelson) wrote: > We need something that will translate these screen > captures into a higher resolution so that the quality will > be maintained when these images are printed out on a 300 > dpi or greater printer. This will be an interesting project. Here are a few thoughts. There's a screen capture utility on the Mac that captures the PICT drawing commands into a PICT file instead of capturing the bits on the screen. That should improve certain kinds of screen captures. In particular, you get a PICT with real characters and fonts, instead of coarse bitmaps. In other words the bits and lines look like bits and lines, but the characters are smooth. I guess this is not much help if your app is running on UNIX but I thought I'd mention it. Bitmapped screen captures often capture dithering patterns used on screen. You must not print these - they'll alias into Moire checkerboards in your book. You mention "commercially-produced guides" - there's examples of screenshot checkerboard Moire in IBM's OS/2 WARP manual, and when Hayden Books produced The Tao of AppleScript, 2nd edition they JPEG-compressed their screenshots for gawd's sake! There's fringes and ringing around the edges. Looks like bad video. So it seems to me that you and I are on the leading edge as much as they are. Even if you avoid systemic dithering, some ancient software still lingering in contemporary operating systems has dither built-in. For example, on a Mac the elevator bars are dithered no matter what screen resolution you are using. Use Photoshop or something similar to touch up the screen captures to fill dithered areas with uniform grey levels. This is the approach thatt I took in a document that I wrote that has a lot of screen shots - check out the Mac-Internet docs linked from the Mac section of my home page. A similar problem is software that writes closely-spaced lines to the screen, as in the racing stripes of an active window's titlebar on the Mac. These are OK at 72 dpi, and reproduce without arifact at 144, 216 and 288 dpi. But reproduction at other dpi settings - 300, say! - produces uneven line spacing. You have to choose scale factors carefully, and in awareness of the resolution capability of the output device. If you avoid dithering in the screen shot - perhaps by capturing the app running in 24 bit colour - then you could use Adobe Streamline to trace the bitmap. Then you could scale to any size, any resolution. You would have to coerce Streamline to turn sharp corners at every pixel. I have no experience with this but I am certain that you could force it to do this, even if you had to pass it a bitmap image resixed to sixteen times. If you resize a bitmapped screenshot in Photoshop, choose Nearest Neighbor Interpolation so as to replicate pixels, in one of the rare instances where this is the right thing to do. Please report what you find back to the rest of us! C. Charles Poynton [Mac Eudora, MIME, BinHqx] tel: 416 486 3271 fax: 416 486 3657