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Thecommandto startgraphicsmustbetransmittednext.Thiscommandis:
<ESC>*rn A
wherencantakeavalueofeitherOor 1.Whenn=O,themarginforprinting
graphics will be the left-most printable edge of the page (this is not
necessarilythe same as the left text margin).If n=l, the left marginfor
graphicsis set to the currentprintposition,and anygraphicsimage will
appearonlyto the rightof thatmargin.
Threegraphicdatacompressionformatsareavailablefordatatransfer.The
data compressionformat to be usedis selectedusing the followingcom-
mand:
<ESC>*bn M
wheren can takethevalueO,1 or 2. Anyotherwilueis interpretedasO.A
fill discussionof datacompressiontechniquesis outsidethe scopeof this
manual,buta briefexplanationof thiscommandshouldbe useful.
.
.
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Wheren=O,no encodingtakesplace,anda simplebinarytransfertakes
place.Bit7 ofthefirstbytecorrespondstothefirstdotin a rasterrow,bit
6 to the second,andsoon.
Where n=l, run-lengthencodingtakes place. This is a compression
techniquewherethedatais dividedintopaics;thefirstbyteof eachpair
servingastherepetitioncountforthedatain thesecondpair.If the first
byteof thepairisequaltozero,thedatainthesecondbyteisnotrepeated.
Wheren=2,thedata to followis in TaggedImageFile Format(TIFF)
confofrningto RV.4.Ostandards.The demandsof spacedo not allowa
detailed discussion of TIFF standardshere, but briefly, TIFF files
combinefeaturesofnon-encodedandnon-encoded.fdes.Manyproprie-
tarygraphicspackagesuseTIFFencodingwhenstoringandtransmitting
graphicdata.
When transferringraster graphic data, each line of raster data must be
prefixedby thecommand:
<ESC>*bn W
wherengivesthenumberofdatabytestofollow(themaximumis255before
anothersuchcommandissent).Thisdatamustfollowthecompressionrules
setin thepreviouscommand.Forinstance,aTIFFimageinterpretedinany
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