AW: [Leica] Erwin's adventures in digiland. part 1 and 2

[Michael Dienert <MDienert@foq.de>]

hello jean-claude,

on your monitor, every pixel is coded as a 24 bit - word. 8 bit for each
of the colors red, green and blue. this way the intensity of every of
the 3 electron beams of your cathode ray tube can be modulated in 255
steps.

if you want to print the image on a printer you cannot modulate the dot
size the ink nozzels produce with such a high (8bit = 255 steps)
resolution. therfore one uses a trick: every 'pixel' on the printout is
printed as a matrix of eg. 2x2 or 4x4 ink-drops.
using the 2x2 matrix the resolution of your printer is diveded by 4 but
you gain a factor of 4 to represent the intensity (density).

using the 4x4 matrix the resolution is decreased by 16. 

yours

michael



> -----Ursprüngliche Nachricht-----
> Von:	Jean-Claude Berger [SMTP:jcberger@imaginet.fr]
> Gesendet am:	Freitag, 13. August 1999 12:53
> An:	leica-users@mejac.palo-alto.ca.us
> Betreff:	RE: [Leica] Erwin's adventures in digiland. part 1 and 2
> 
> Hello Erwin,
> 
> Could this be a typo? I thought that each pixel was represented by 24
> or 48 bits. How can 4 pixels represent 1 pixel?
> 
> > interpolation. Remember that 4 pixels are needed to record
> > one image
> > pixel.
> 
> On your second article, you say :
> 
> > As the typical inkjet printer has 6 colors only a limited range of
> > colors and colorshades can be produced. All other colors and shades
> > demand the use of a halftone or raster technique. If the printer
> > would use a 2x2 matrix  5 additional shades can be produced. If we
> > need the full range of shades a 16x16 matrix will b used.
> 
> Could you elaborate about the "5 additional shades can be produced"?
> 
> As far as I remember, on 6 colors printers, there are 4 (black
> included) basic inks plus 3 see-through ones. So one dot may have 20
> "colors/shades" (no ink, ink 1, 2, 3,..6, black, 1+4, 1+5, 1+6, 2+4,
> ...., 6+6). So a matrix of 4 dots will present 20 power 4
> combinations. I do agree that some combinations are equivalent if we
> consider only the global aspect of the matrix. For example, the square
> 
> A B
> A B
> 
> will have the same color than the squares
> 
> B A
> B A
> 
> or
> 
> A A
> B B
> 
> but it will not give the same effect when the firmware uses
> anti-aliasing algorithms that is the case, if my memory serves well,
> with PCL 5 or PhotoEnhance.
> 
> Moreover, the 750 and 1200 Epson printers are said to be able to
> control the amount of projected ink. That may lead to a greater number
> of possibilities, no?
> 
> 
> All the best.
> 
> 
>  ---
>  Jean-Claude Berger (jcberger@jcberger.com)
>  Systems and RDBMS consultant (MCSE), Lyon, France
>  http://www.jcberger.com
>