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From: daveb@cbmvax.cbm.UUCP (Dave Berezowski)
Newsgroups: net.micro.amiga
Subject: Re: Printer Driver for Toshiba P1340
Message-ID: <940@cbmvax.cbmvax.cbm.UUCP>
Date: Tue, 28-Oct-86 22:29:28 EST
Article-I.D.: cbmvax.940
Posted: Tue Oct 28 22:29:28 1986
Date-Received: Wed, 29-Oct-86 02:42:05 EST
References: <3117@ece-csc.UUCP>
Reply-To: daveb@cbmvax.UUCP (Dave Berezowski)
Organization: Commodore Technology, West Chester, PA
Lines: 56

In article <3117@ece-csc.UUCP> mark@ece-csc.UUCP (Mark Lanzo) writes:
>Questions, questions, and more questions...
>
>I have written a printer driver for a Toshiba P1340 printer.
>
>My biggest question pertains to graphics dumps.  When I print pictures,
>the shading comes out very poorly.  White prints as white, but other
>colors generally print in various _very_ dark shades of gray, even if the
>color is very bright on the screen (such as yellow).  The dithering
>algorithm seems not to work very well; printed images have next to no contrast,
>if you ignore white.  I've seen this also with images dumped on some 
>other printers, and know that there are others out there who also would
>like to have an answer about this.  So how about it?  Do the dithering
>routines in the Amiga just work terribly poorly, or am I doing something
>wrong?   ... before someone suggests it, YES I DO HAVE "grey-scale" set
>in preferences.
>

	Mark, as the author of the graphic's side of the printer drivers,
let me assure you that the dithering algorithms have been tested thoroughly
on a wide range of printers by numerous individuals at CBM-Amiga.

	A couple of thoughts come to mind concerning your problem:

1. If memory serves, the Toshiba P1340 has a 180 and 360 dpi graphics mode.
	Make sure that the dpi that you have implemented is the same as
	the what you are telling the system. ie. you may have implemented
	180 dpi but told the system that the Toshiba does 200 dpi.

2. Printers that implement a higher density by OVERLAPING dots TEND to
	produce darker prints as the area of overlap produces a darker
	dot. Have you implemented an overlaping dot gfx dump? If so, try
	a non-overlapping one.

3. Strange as it may sound, double (and triple) check your algorithm
	in your gfx dump code. Here is an easy way to verify that it
	is correct. Create a screen or window with the 16 shades of black
	(thats 000, 111, 222, etc up to fff in rgb values). Dump this
	to the printer as a large dump (ie 80 columns). Starting at the
	lightest color, you should see a gradual increase in the number
	of dots/fixed_area on the printer. The dither algorithm uses a
	4 x 4 dither matrix, thus:
	000 corresponds to 0 dots per 4 x 4
	111      "         1
	222      "         2
		etc
	eee      "         14
	fff      "         16 (uses all 16 here so that full colors are solid)


	Hope I've been helpful.

	Regards, David Berezowski

Disclaimer: I no longer work for CBM-Amiga, (although I sometimes do work
for them) and my views are my own.