davis@MASIG4.OCEAN.FSU.EDU (Alan Davis) (06/02/91)
I am trying to use a Tektronix Phaser PX on a PI 4D/35 3.3.2 without much
luck. I have been using both tocolps and tops to make color PostScript which
I am sending to the printer. The quality of the print is extremely poor, the
image comes out with a very mottled appearence, like something happened
during the dithering, ie the whole image is speckled with white dots. I assume
you must be able to make normal prints on this printer and would like to hear
from someone who has done this already. All my other experience is with the
4693D which makes very good prints. Thanks in advance.
_______________________________________________________________________________
Alan Davis | INTERNET davis@masig1.ocean.fsu.edu
MS B-174, Love 008A | SPAN fsu1::davis
Mesoscale Air-Sea Inter. Group | BITNET davis%masig1.ocean.fsu.edu@fsuavm
Florida State University | Phone 904-644-3798
Tallahassee, FL 32306-3041 | FAX 904-644-8579
_______________________________________________________________________________bernie@umbc3.umbc.edu (Bernard J. Duffy) (06/04/91)
In article <9106012100.AA28850@masig4.ocean.fsu.edu> davis@MASIG4.OCEAN.FSU.EDU (Alan Davis) writes: > > I am trying to use a Tektronix Phaser PX on a PI 4D/35 3.3.2 without much >luck. I have been using both tocolps and tops to make color PostScript which >I am sending to the printer. The quality of the print is extremely poor, the >image comes out with a very mottled appearence, like something happened >during the dithering, ie the whole image is speckled with white dots. I assume I don't have a color postscript printer, but I do have the GNU gs previewer. The output from the tocolps program (obtained from sgi.com) didn't render the .rgb plot in full color. The resultant .ps file only had about 7 colors (includes black and white) and the original .rgb had a rainbow of at least 256 colors. It turned a plot that had several steps worth of a contour-like coloring into 5 steps. I then tried the topost (I think this was on ftp.brl.mil) and that didn't work at all (no real data ended up in the .ps file). I then tried the ppm utilities (giftoppm ... ppmtops) and got the "dithered" like output that Alan got. I also checked out the sdsc.edu imtools' imconv and found it didn't have a picture to color postscript conversion. I did make one run of the utility from .rgb to .ps (imconv junk.rgb junk.ps) and it didn't do any dithering or RGB==>Grayscale conversions. SO.... does anybody know of another "pix" to color postscript converters out there. The ones I've mentioned above use colorimage PS operator and I'm beginning to think it doesn't do a good job. I'm surprised to see on one-to-one converters for color pictures like .ppm or .gif ! >you must be able to make normal prints on this printer and would like to hear >from someone who has done this already. All my other experience is with the >4693D which makes very good prints. Thanks in advance. ^^^^^^^^^^^^^^^^^^ me too... -- Bernie Duffy Systems Programmer II | Bitnet : BERNIE@UMBC2 Academic Computing Services - L005e | Internet : BERNIE@UMBC2.UMBC.EDU Univ. of Maryland Baltimore County | UUCP : ...!uunet!umbc3!bernie Baltimore, MD 21228 (U.S.A.) | W: (301) 455-3231 H: (301) 744-2954
blythe@sgi.com (David R. Blythe) (06/05/91)
>In article <9106012100.AA28850@masig4.ocean.fsu.edu> davis@MASIG4.OCEAN.FSU.EDU (Alan Davis) writes: > > I am trying to use a Tektronix Phaser PX on a PI 4D/35 3.3.2 without much >luck. I have been using both tocolps and tops to make color PostScript which >I am sending to the printer. The quality of the print is extremely poor, the >image comes out with a very mottled appearence, like something happened >during the dithering, ie the whole image is speckled with white dots. I assume > > tocolps should be adequate for the job since it does nothing more than copy the bits to the file for imaging by the printer. It does, however, set the screendensity and screenangle for each of the magenta, cyan, yellow and black primaries. These are undoubtably causing your problems. That and possibly your expectations may be too high. You might try deleting the manipulations of the angles and densities from the PostScript file since these are often better left as the manufacturers defaults unless you know what you are doing. Otherwise, the printer documentation may give you some clue to alternate values to try. I couldn't begin to guess myself :-(. david blythe blythe@sgi.com
davidh8@pogo.WV.TEK.COM (David Haight) (06/05/91)
In article <1991Jun4.210057.29808@odin.corp.sgi.com> blythe@sgi.com (David R. Blythe) writes: >>In article <9106012100.AA28850@masig4.ocean.fsu.edu> davis@MASIG4.OCEAN.FSU.EDU (Alan Davis) writes: >> >> I am trying to use a Tektronix Phaser PX on a PI 4D/35 3.3.2 without much >>luck. I have been using both tocolps and tops to make color PostScript which >>I am sending to the printer. The quality of the print is extremely poor, the >>image comes out with a very mottled appearence, like something happened >>during the dithering, ie the whole image is speckled with white dots. I assume >> >> > >tocolps should be adequate for the job since it does nothing more than >copy the bits to the file for imaging by the printer. It does, however, >set the screendensity and screenangle for each of the magenta, cyan, yellow >and black primaries. These are undoubtably causing your problems. That >and possibly your expectations may be too high. You might try deleting >the manipulations of the angles and densities from the PostScript file >since these are often better left as the manufacturers defaults unless >you know what you are doing. Otherwise, the printer documentation may >give you some clue to alternate values to try. I couldn't begin to guess >myself :-(. > > david blythe > blythe@sgi.com The problem is "blithering" or double dithering. Try downloading this first. %! %% Patch to the setscreen operator to avoid unwanted behaviour and to %% increase speed, but at the expense of disabling patterning. Some %% applications set their own screens, but these generally look worse than %% the built-in ones in the Tektronix Phaser printers, so we want to use %% the internal ones. %% %% The patch simply executes the spot function procedure four times, once %% at each corner of the halftone cell, and throws the results of those %% executions away. Then all three arguments to setscreen are discarded. %% %% The proc would not have to be executed at all if it was not for those %% applications that set variables inside of the proc and refer to them %% outside of the proc (for determining the threshold gray level of a %% pattern). GEM applications and Broderbund TypeStyler do this. Normal %% setscreen operation could execute this proc thousands of times. %% %% This patch will only apply itself once. The patch can be circumvented %% by directly referencing the setscreen definition in systemdict, as in %% "systemdict /setscreen get exec" serverdict begin 0 exitserver /setscreen load type /operatortype eq % patch only if not patched already { /setscreen { .99999 .99999 2 index exec pop % execute proc, discard result .99999 -.99999 2 index exec pop -.99999 .99999 2 index exec pop -.99999 -.99999 2 index exec pop pop pop pop % discard setscreen arguments } bind def (Setscreen patch downloaded) = flush } if %%EOF
art@lsr-vax.UUCP (Art Hays - PSTAFF) (06/07/91)
I would appreciate more info about PostScript Phasers vs. rgb Phasers as well. Tektronix sells two versions of the Phaser II- one with PostScript and one that handles SGI or Sun raster files directly. You cant get both in the same printer. Is it true that the PostScript version cannot match the quality of the raster version? What disturbs me is that one gets different results with the PostScript printer depending on which rgb -> PostScript converter is used. Art Hays, Nat. Eye Institute, uunet!lsr-vax!art Nat. Institutes of Health, Bethesda, MD (301) 496-7143