diff options
| author | Didier Raboud <odyx@debian.org> | 2014-04-16 08:13:23 +0200 |
|---|---|---|
| committer | Didier Raboud <odyx@debian.org> | 2014-04-16 08:13:23 +0200 |
| commit | d7d42f6c969dc54157d85b7b6b611581bbfa7595 (patch) | |
| tree | dfa630457b374b77f1f128cbc9104ea2d6963575 /doc/developer/reference-html/c1717.html | |
| parent | ccd50c2bd4db57503722816aa23a5092cbe69f40 (diff) | |
Imported Upstream version 5.2.10~pre1
Diffstat (limited to 'doc/developer/reference-html/c1717.html')
| -rw-r--r-- | doc/developer/reference-html/c1717.html | 294 |
1 files changed, 0 insertions, 294 deletions
diff --git a/doc/developer/reference-html/c1717.html b/doc/developer/reference-html/c1717.html deleted file mode 100644 index 8d788c0..0000000 --- a/doc/developer/reference-html/c1717.html +++ /dev/null @@ -1,294 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> -<HTML -><HEAD -><TITLE ->Weaving for inkjet printers</TITLE -><META -NAME="GENERATOR" -CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK -REL="HOME" -TITLE="The Developer's Guide to Gutenprint" -HREF="book1.html"><LINK -REL="PREVIOUS" -TITLE="Appropriate Remote Commands" -HREF="x1669.html"><LINK -REL="NEXT" -TITLE="Weaving algorithms" -HREF="x1734.html"><META -http-equiv="Content-Type" -content="text/html; charset=@encoding@"></HEAD -><BODY -CLASS="chapter" -><DIV -CLASS="NAVHEADER" -><TABLE -SUMMARY="Header navigation table" -WIDTH="100%" -BORDER="0" -CELLPADDING="0" -CELLSPACING="0" -><TR -><TH -COLSPAN="3" -ALIGN="center" ->The Developer's Guide to Gutenprint</TH -></TR -><TR -><TD -WIDTH="10%" -ALIGN="left" -VALIGN="bottom" -><A -HREF="x1669.html" -ACCESSKEY="P" ->Prev</A -></TD -><TD -WIDTH="80%" -ALIGN="center" -VALIGN="bottom" -></TD -><TD -WIDTH="10%" -ALIGN="right" -VALIGN="bottom" -><A -HREF="x1734.html" -ACCESSKEY="N" ->Next</A -></TD -></TR -></TABLE -><HR -ALIGN="LEFT" -WIDTH="100%"></DIV -><DIV -CLASS="chapter" -><H1 -><A -NAME="AEN1717" -></A ->Chapter 6. Weaving for inkjet printers</H1 -><DIV -CLASS="TOC" -><DL -><DT -><B ->Table of Contents</B -></DT -><DT -><A -HREF="c1717.html#AEN1719" ->Introduction</A -></DT -><DT -><A -HREF="x1734.html" ->Weaving algorithms</A -></DT -></DL -></DIV -><DIV -CLASS="sect1" -><H1 -CLASS="sect1" -><A -NAME="AEN1719" ->Introduction</A -></H1 -><P -> The Epson Stylus Color/Photo printers don't have memory to print - using all of the nozzles in the print head. For example, the - Stylus Photo 700/EX has 32 nozzles. At 720 dpi, with an 8" wide - image, a single line requires ((8 × 720 × 6) / 8) - bytes, or 4320 bytes (because the Stylus Photo printers have 6 - ink colors). To use 32 nozzles per color would require 138240 - bytes. It's actually worse than that, though, because the - nozzles are spaced 8 rows apart. Therefore, in order to store - enough data to permit sending the page as a simple raster, the - printer would require enough memory to store 256 rows, or - 1105920 bytes. Considering that the Photo EX can print 11" - wide, we're looking at more like 1.5 MB. In fact, these - printers are capable of 1440 dpi horizontal resolution. This - would require 3 MB. The printers actually have 64K-256K. - </P -><P -> With the newer (740/750 and later) printers it's even worse, - since these printers support multiple dot sizes; of course, the - even newer 2880×720 printers don't help either. - </P -><P -> Older Epson printers had a mode called - MicroWeave<SUP ->™</SUP ->. In this mode, the - host fed the printer individual rows of dots, and the printer - bundled them up and sent them to the print head in the correct - order to achieve high quality. This MicroWeave mode still works - in new printers, but in some cases the implementation is very - minimal: the printer uses exactly one nozzle of each color (the - first one). This makes printing extremely slow (more than 30 - minutes for one 8.5×11" page), although the quality is - extremely high with no visible banding whatsoever. It's not - good for the print head, though, since no ink is flowing through - the other nozzles. This leads to drying of ink and possible - permanent damage to the print head. - </P -><P -> By the way, although the Epson manual says that microweave mode - should be used at 720 dpi, 360 dpi continues to work in much the - same way. At 360 dpi, data is fed to the printer one row at a - time on all Epson printers. The pattern that the printer uses - to print is very prone to banding. However, 360 dpi is - inherently a low quality mode; if you're using it, presumably - you don't much care about quality. It is possible to do - microweave at 360 DPI, with significantly improved quality. - </P -><P -> Except for the Stylus Pro printers (5000, 5500, 7000, 7500, - 9000, 9500, and when it's released the 10000), which can do - microweave at any resolution, printers from roughly the Stylus - Color 600 and later do not have the capability to do MicroWeave - correctly in many cases (some printers can do MicroWeave - correctly at 720 DPI). Instead, the host must arrange the - output in the order that it will be sent to the print head. - This is a very complex process; the jets in the print head are - spaced more than one row (1/720") apart, so we can't simply send - consecutive rows of dots to the printer. Instead, we have to - pass e. g. the first, ninth, 17th, 25th... rows in order for - them to print in the correct position on the paper. This - interleaving process is called "soft" weaving. - </P -><P -> This decision was probably made to save money on memory in the - printer. It certainly makes the driver code far more - complicated than it would be if the printer could arrange the - output. Is that a bad thing? Usually this takes far less CPU - time than the dithering process, and it does allow us more - control over the printing process, e.g. to reduce banding. - Conceivably, we could even use this ability to map out bad jets. - </P -><P -> Interestingly, apparently the Windows (and presumably Macintosh) - drivers for most or all Epson printers still list a - “microweave” mode. Experiments have demonstrated - that this does not in fact use the “microweave” mode - of the printer. Possibly it does nothing, or it uses a - different weave pattern from what the - “non-microweave” mode does. This is unnecessarily - confusing, at least for people who write drivers who try to - explain them to people who don't. - </P -><P -> What makes this interesting is that there are many different - ways of of accomplishing this goal. The naive way would be to - divide the image up into groups of 256 rows (for a printer with - 32 jets and a separation of 8 rows), and print all the mod8=0 - rows in the first pass, mod8=1 rows in the second, and so forth. - The problem with this approach is that the individual ink jets - are not perfectly uniform; some emit slightly bigger or smaller - drops than others. Since each group of 8 adjacent rows is - printed with the same nozzle, that means that there will be - distinct streaks of lighter and darker bands within the image (8 - rows is 1/90", which is visible; 1/720" is not). Possibly worse - is that these patterns will repeat every 256 rows. This creates - banding patterns that are about 1/3" wide. - </P -><P -> So we have to do something to break up this patterning. - </P -><P -> Epson do not publish the weaving algorithms that they use in - their bundled drivers. Indeed, their developer web site - (http://www.ercipd.com/isv/edr_docs.htm) does not even describe - how to do this weaving at all; it says that the only way to - achieve 720 dpi is to use MicroWeave. It does note (correctly) - that 1440 dpi horizontal can only be achieved by the driver - (i. e. in software). The manual actually makes it fairly clear - how to do this (it requires two passes with horizontal head - movement between passes), and it is presumably possible to do - this with MicroWeave. - </P -><P -> The information about how to do this is apparently available - under non-disclosure agreement (NDA). It's actually easy enough - to reverse engineer what's inside a print file with a simple - Perl script, which is supplied with the Gutenprint distribution - as tests/parse-escp2. In any event, we weren't particularly - interested in the weaving patterns Epson used. There are many - factors that go into choosing a good weaving pattern; we're - learning them as we go along. Issues such as drying time - (giving the ink a few seconds more or less to dry can have - highly visible effects) affect the quality of the output. - </P -><P -> The Uniprint GhostScript driver has been able to do weaving for - a long time. It uses patterns that must be specified for each - choice of resolution and printer. We preferred an algorithmic - approach that computes a weave pattern for any given choice of - inputs. This obviously requires extensive testing; we developed - a test suite specifically for this purpose. - </P -></DIV -></DIV -><DIV -CLASS="NAVFOOTER" -><HR -ALIGN="LEFT" -WIDTH="100%"><TABLE -SUMMARY="Footer navigation table" -WIDTH="100%" -BORDER="0" -CELLPADDING="0" -CELLSPACING="0" -><TR -><TD -WIDTH="33%" -ALIGN="left" -VALIGN="top" -><A -HREF="x1669.html" -ACCESSKEY="P" ->Prev</A -></TD -><TD -WIDTH="34%" -ALIGN="center" -VALIGN="top" -><A -HREF="book1.html" -ACCESSKEY="H" ->Home</A -></TD -><TD -WIDTH="33%" -ALIGN="right" -VALIGN="top" -><A -HREF="x1734.html" -ACCESSKEY="N" ->Next</A -></TD -></TR -><TR -><TD -WIDTH="33%" -ALIGN="left" -VALIGN="top" ->Appropriate Remote Commands</TD -><TD -WIDTH="34%" -ALIGN="center" -VALIGN="top" -> </TD -><TD -WIDTH="33%" -ALIGN="right" -VALIGN="top" ->Weaving algorithms</TD -></TR -></TABLE -></DIV -></BODY -></HTML ->
\ No newline at end of file |