Conference bulova::decw_jan-89_to_nov-90

3679.0. "Help needed with Printscreen quality and speed to an LJ250" by WHYNOW::NEWMAN (What, me worry? YOU BET!) Fri Nov 16 1990 17:18

I have a customer who is having problems printing a screen image to their 
LJ250.  I read through the notes pertaining to the LJ250 but am not sure 
if they pertain to my problem.  If my questions are redundant I 
apologize...

My customer has written a DECwindows application program that displays a 
series of color objects/lines/... on the workstation.  In order to get a 
hardcopy of the screen printed to an LJ250 they do the following...

1)  They use the session manager "Capture Portion of Screen" to capture the 
portion of the screen they want printed to a SIXEL file.
2)  They then print the file to the LJ250 that is connected to the system 
via a standard VMS Print Queue.

They have two complaints...

1)  The process is VERY SLOW.  Whether they first capture the screen and 
then print it or do it all in one step, the claim that it takes over 1 hour 
to accomplish the task.

2)  When the file does print the print quality is poor.

In talking to the customer about this issue I suggested that they 
investigate UTOX, an ASSETS product, to resolve complaint #1.  It seems to 
capture the screen image into a SIXEL file very fast.

Regarding the print quality issue, it is my belief that it is due to the 
colors that they are displaying and how the LJ250 "mixes" colors to display 
the desired color.  I can run excellent quality prints on my LJ250 and also 
very poor ones.  I believe it has to do with the colors that are chosen.  
Also, I believe it has to do with the resolution (dpi) of the LJ250.

I know nothing about programming a DECwindows application.  The customer 
said that he has a "table" of colors to pick from to display via his 
application.  He was wondering if anyone knows what colors print better 
than others on the LJ250.

I hope my explanation is clear and someone can give me some advice for the 
customer.  If it is not clear, just ask and I will attempt to clarify it.

Thanks for all your help

Bob Newman

The LJ250 Programmer's Reference Manual lists in Appendix D the colors the
LJ250 is capable of printing.  The LJ250 has a fixed colormap of 256 colors.
If a particular color to be printed is not one of those 256 colors, it will
be approximated and printed as one of those 256.  Its approximation is not
always that good.

The customer can see those 256 colors by printing the self-test color
pallate.

1. (With paper in the machine, ) turn printer power off
2. Press and hold the READY and DEC/PCL buttons, while momentarily pressing
   the power switch
3. After about 2 seconds, release the READY and DEC/PCL buttons
4. The printer will print the test sheet.

Is there any way to know which of the DECwindows colors map to which of the 
256 possible LJ250 colors?

>Is there any way to know which of the DECwindows colors map to which of the 
>256 possible LJ250 colors?

There's no simple way other than printing out the test color-pallate sheet
and holding it up to the screen and seeing which colors match.  In fact,
that is probably the best way to go.  The actual appearance of colors of
certain RGB color values will not match between the screen and the printer.
This is certain because the color range of the different devices were never
made to match.  100% red for instance on the screen will not look the same
as 100% red on the printer.  There is also a lot of room for variation among
the same devices due to, among other things, different screen brightness,
contrast, and color gain settings.

So the best way to determine matches is to match a printed sample to the
screen.

-Mike