On Fri, 31 Oct 2003 12:21:48 +0100 Michal Kvasnicka <[EMAIL PROTECTED]> wrote:
> I typeset a church bulleting. It is printed on a laserjet printer (600 > > dpi), and then copied on a copy machine. As for letters, all is right. > > But figures (photos) are this way spoiled. I guess it would help > either to force PDF to print the figures in some very low resolution > (150 dpi), or (probably better) to dither the figures and include them > in PNG (instead of ordinary JPEG). Can some of you tell me how to do > it? I tried ImageMagick's convert to dither the photos, but outcomes > were really poor. Is there some good free software for this (in the > best case in Linux)? Or can I do it some way in PDF? I suspect you need to halftone the photos before including them. All the gray pixels must be converted into a pattern of black and white equivalents. On Linux you have the netpbm package which has everything you need. The specific utility is pgmtopbm with various switches. There are other utilities for converting to and from the netpbm file formats. Here is an example of a pipeline I use to do several manipulations at once: pnmscale -width=1950 pleiades.pnm | pnmsmooth -size 5 5 | pgmtopbm -fs -value 0.5 | pnmtopng > pleiades.png pnmscale: expand to a known size pnmsmooth: try to obscure the halftone of the original photo pgmtopbm: apply new halftone, -fs = "floyd-steinberg" halftoning pnmtopng: convert to png for inclusion into pdf The trouble with halftone images is that they are not resolution-independent. You may have to adjust the image size and parameters depending on your printer. Also, halftoned images do not display well in some graphics programs, although acroread does a pretty good job when they are included in pdf files. -Bill -- Sattre Press The King in Yellow http://sattre-press.com/ by Robert W. Chambers [EMAIL PROTECTED] http://kiy.sattre-press.com/ _______________________________________________ ntg-context mailing list [EMAIL PROTECTED] http://www.ntg.nl/mailman/listinfo/ntg-context
