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Code Editor : spec-raster.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML>

<HEAD>
	<TITLE>CUPS Raster Format</TITLE>
	<LINK REL="STYLESHEET" TYPE="text/css" HREF="../cups-printable.css">
</HEAD>
<BODY>

<H1 CLASS="title">CUPS Raster Format</H1>

<P>CUPS raster files are device-dependent raster image files that
contain a PostScript page device dictionary and device-dependent
raster imagery for each page in the document. These files are
used to transfer raster data from the PostScript and image file
RIPs to device-dependent filters that convert the raster data to
a printable format.</P>

<P>CUPS 1.0 and 1.1 used a version 1 raster format. CUPS 1.2
introduced version 2 (compressed) and version 3 (uncompressed)
formats that are a superset of the version 1 format. Applications
using the CUPS Imaging API (the cupsRaster* functions) can read
all formats without code changes.</P>

<P>The registered MIME media type for CUPS raster files is
<CODE>application/vnd.cups-raster</CODE>.</P>

<H2 CLASS="title"><A NAME="V1">Version 1 Raster File Format</A></H2>

<P>A version 1 raster file begins with a 32-bit synchronization
word: 0x52615374 ("RaSt") for big-endian architectures and
0x74536152 ("tSaR") for little-endian architectures. The writer
of the raster file will use the native word order, and the reader
is responsible for detecting a reversed word order file and
swapping bytes as needed. The CUPS Imaging API raster functions
perform this function automatically.</P>

<P>Following the synchronization word are a series of raster
pages. Each page starts with a page device dictionary header and
is followed immediately by the (uncompressed, raw) raster data
for that page.</P>

<DIV CLASS="table"><TABLE SUMMARY="CUPS Version 1 Raster Page Device Dictionary">
<CAPTION><A NAME="TABLE1">Table 1: CUPS Version 1 Raster Page Device Dictionary</A></CAPTION>
<THEAD>
<TR>
	<TH>Bytes</TH>
	<TH>Type</TH>
	<TH>Description</TH>
	<TH>Values</TH>
</TR>
</THEAD>
<TBODY>
<TR>
	<TD>0-63</TD>
	<TD>C String</TD>
	<TD>MediaClass</TD>
	<TD>Media class string</TD>
</TR>
<TR>
	<TD>64-127</TD>
	<TD>C String</TD>
	<TD>MediaColor</TD>
	<TD>Media color string</TD>
</TR>
<TR>
	<TD>128-191</TD>
	<TD>C String</TD>
	<TD>MediaType</TD>
	<TD>Media type string</TD>
</TR>
<TR>
	<TD>192-255</TD>
	<TD>C String</TD>
	<TD>OutputType</TD>
	<TD>Output type string</TD>
</TR>
<TR>
	<TD>256-259</TD>
	<TD>Unsigned Integer</TD>
	<TD>AdvanceDistance</TD>
	<TD>0 to 2<SUP>32</SUP> - 1 points</TD>
</TR>
<TR>
	<TD>260-263</TD>
	<TD>Unsigned Integer</TD>
	<TD>AdvanceMedia</TD>
	<TD>0 = Never advance roll<BR>
	1 = Advance roll after file<BR>
	2 = Advance roll after job<BR>
	3 = Advance roll after set<BR>
	4 = Advance roll after page</TD>
</TR>
<TR>
	<TD>264-267</TD>
	<TD>Unsigned Integer</TD>
	<TD>Collate</TD>
	<TD>0 = do not collate copies<BR>
	1 = collate copies</TD>
</TR>
<TR>
	<TD>268-271</TD>
	<TD>Unsigned Integer</TD>
	<TD>CutMedia</TD>
	<TD>0 = Never cut media<BR>
	1 = Cut roll after file<BR>
	2 = Cut roll after job<BR>
	3 = Cut roll after set<BR>
	4 = Cut roll after page</TD>
</TR>
<TR>
	<TD>272-275</TD>
	<TD>Unsigned Integer</TD>
	<TD>Duplex</TD>
	<TD>0 = Print single-sided<BR>
	1 = Print double-sided</TD>
</TR>
<TR>
	<TD>276-283</TD>
	<TD>Unsigned Integers (2)</TD>
	<TD>HWResolution</TD>
	<TD>Horizontal and vertical resolution in dots-per-inch.</TD>
</TR>
<TR>
	<TD>284-299</TD>
	<TD>Unsigned Integers (4)</TD>
	<TD>ImagingBoundingBox</TD>
	<TD>Four integers giving the left, bottom, right, and top positions
	of the page bounding box in points</TD>
</TR>
<TR>
	<TD>300-303</TD>
	<TD>Unsigned Integer</TD>
	<TD>InsertSheet</TD>
	<TD>0 = Do not insert separator sheets<BR>
	1 = Insert separator sheets</TD>
</TR>
<TR>
	<TD>304-307</TD>
	<TD>Unsigned Integer</TD>
	<TD>Jog</TD>
	<TD>0 = Do no jog pages<BR>
	1 = Jog pages after file<BR>
	2 = Jog pages after job<BR>
	3 = Jog pages after set</TD>
</TR>
<TR>
	<TD>308-311</TD>
	<TD>Unsigned Integer</TD>
	<TD>LeadingEdge</TD>
	<TD>0 = Top edge is first<BR>
	1 = Right edge is first<BR>
	2 = Bottom edge is first<BR>
	3 = Left edge is first</TD>
</TR>
<TR>
	<TD>312-319</TD>
	<TD>Unsigned Integers (2)</TD>
	<TD>Margins</TD>
	<TD>Left and bottom origin of image in points</TD>
</TR>
<TR>
	<TD>320-323</TD>
	<TD>Unsigned Integer</TD>
	<TD>ManualFeed</TD>
	<TD>0 = Do not manually feed media<BR>
	1 = Manually feed media</TD>
</TR>
<TR>
	<TD>324-327</TD>
	<TD>Unsigned Integer</TD>
	<TD>MediaPosition</TD>
	<TD>Input slot position from 0 to N</TD>
</TR>
<TR>
	<TD>328-331</TD>
	<TD>Unsigned Integer</TD>
	<TD>MediaWeight</TD>
	<TD>Media weight in grams per meter squared</TD>
</TR>
<TR>
	<TD>332-335</TD>
	<TD>Unsigned Integer</TD>
	<TD>MirrorPrint</TD>
	<TD>0 = Do not mirror prints<BR>
	1 = Mirror prints</TD>
</TR>
<TR>
	<TD>336-339</TD>
	<TD>Unsigned Integer</TD>
	<TD>NegativePrint</TD>
	<TD>0 = Do not invert prints<BR>
	1 = Invert prints</TD>
</TR>
<TR>
	<TD>340-343</TD>
	<TD>Unsigned Integer</TD>
	<TD>NumCopies</TD>
	<TD>1 to 2<SUP>32</SUP> - 1</TD>
</TR>
<TR>
	<TD>344-347</TD>
	<TD>Unsigned Integer</TD>
	<TD>Orientation</TD>
	<TD>0 = Do not rotate page<BR>
	1 = Rotate page counter-clockwise<BR>
	2 = Turn page upside down<BR>
	3 = Rotate page clockwise</TD>
</TR>
<TR>
	<TD>348-351</TD>
	<TD>Unsigned Integer</TD>
	<TD>OutputFaceUp</TD>
	<TD>0 = Output face down<BR>
	1 = Output face up</TD>
</TR>
<TR>
	<TD>352-359</TD>
	<TD>Unsigned Integers (2)</TD>
	<TD>PageSize</TD>
	<TD>Width and length in points</TD>
</TR>
<TR>
	<TD>360-363</TD>
	<TD>Unsigned Integer</TD>
	<TD>Separations</TD>
	<TD>0 = Print composite image<BR>
	1 = Print color separations</TD>
</TR>
<TR>
	<TD>364-367</TD>
	<TD>Unsigned Integer</TD>
	<TD>TraySwitch</TD>
	<TD>0 = Do not change trays if selected tray is empty<BR>
	1 = Change trays if selected tray is empty</TD>
</TR>
<TR>
	<TD>368-371</TD>
	<TD>Unsigned Integer</TD>
	<TD>Tumble</TD>
	<TD>0 = Do not rotate even pages when duplexing<BR>
	1 = Rotate even pages when duplexing</TD>
</TR>
<TR>
	<TD>372-375</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsWidth</TD>
	<TD>Width of page image in pixels</TD>
</TR>
<TR>
	<TD>376-379</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsHeight</TD>
	<TD>Height of page image in pixels</TD>
</TR>
<TR>
	<TD>380-383</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsMediaType</TD>
	<TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
</TR>
<TR>
	<TD>384-387</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsBitsPerColor</TD>
	<TD>1, 2, 4, 8 bits for version 1 raster files<BR>
	1, 2, 4, 8, and 16 bits for version 2 raster files</TD>
</TR>
<TR>
	<TD>388-391</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsBitsPerPixel</TD>
	<TD>1 to 32 bits for version 1 raster files<BR>
	1 to 64 bits for version 2 raster files</TD>
</TR>
<TR>
	<TD>392-395</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsBytesPerLine</TD>
	<TD>1 to 2<SUP>32</SUP> - 1 bytes</TD>
</TR>
<TR>
	<TD>396-399</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsColorOrder</TD>
	<TD>0 = chunky pixels (CMYK CMYK CMYK)<BR>
	1 = banded pixels (CCC MMM YYY KKK)<BR>
	2 = planar pixels (CCC... MMM... YYY... KKK...)</TD>
</TR>
<TR>
	<TD>400-403</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsColorSpace</TD>
	<TD>0 = white (sRGB)<BR>
	1 = RGB (sRGB)<BR>
	2 = RGBA (sRGB)<BR>
	3 = black<BR>
	4 = CMY<BR>
	5 = YMC<BR>
	6 = CMYK<BR>
	7 = YMCK<BR>
	8 = KCMY<BR>
	9 = KCMYcm<BR>
	10 = GMCK<BR>
	11 = GMCS<BR>
	12 = WHITE<BR>
	13 = GOLD<BR>
	14 = SILVER<BR>
	15 = CIE XYZ<BR>
	16 = CIE Lab<BR>
	17 = RGBW (sRGB)<BR>
	32 = ICC1 (CIE Lab with hint for 1 color)<BR>
	33 = ICC2 (CIE Lab with hint for 2 colors)<BR>
	34 = ICC3 (CIE Lab with hint for 3 colors)<BR>
	35 = ICC4 (CIE Lab with hint for 4 colors)<BR>
	36 = ICC5 (CIE Lab with hint for 5 colors)<BR>
	37 = ICC6 (CIE Lab with hint for 6 colors)<BR>
	38 = ICC7 (CIE Lab with hint for 7 colors)<BR>
	39 = ICC8 (CIE Lab with hint for 8 colors)<BR>
	40 = ICC9 (CIE Lab with hint for 9 colors)<BR>
	41 = ICCA (CIE Lab with hint for 10 colors)<BR>
	42 = ICCB (CIE Lab with hint for 11 colors)<BR>
	43 = ICCC (CIE Lab with hint for 12 colors)<BR>
	44 = ICCD (CIE Lab with hint for 13 colors)<BR>
	45 = ICCE (CIE Lab with hint for 14 colors)<BR>
	46 = ICCF (CIE Lab with hint for 15 colors)<BR>
	</TD>
</TR>
<TR>
	<TD>404-407</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsCompression</TD>
	<TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
</TR>
<TR>
	<TD>408-411</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsRowCount</TD>
	<TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
</TR>
<TR>
	<TD>412-415</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsRowFeed</TD>
	<TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
</TR>
<TR>
	<TD>416-419</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsRowStep</TD>
	<TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
</TR>
</TBODY>
</TABLE></DIV>

<H2 CLASS="title"><A NAME="V2">Version 2 Raster File Format</A></H2>

<P>A version 2 raster file begins with a 32-bit synchronization
word: 0x52615332 ("RaS2") for big-endian architectures and
0x32536152 ("2SaR") for little-endian architectures. The writer
of the raster file will use the native word order, and the reader
is responsible for detecting a reversed word order file and
swapping bytes as needed. The CUPS Imaging API raster functions
perform this function automatically.</P>

<P>Following the synchronization word are a series of raster
pages. Each page starts with a version 2 page device dictionary
header and is followed immediately by the compressed raster data
for that page.</P>

<DIV CLASS="table"><TABLE SUMMARY="CUPS Version 2 Raster Page Device Dictionary">
<CAPTION><A NAME="TABLE2">Table 2: CUPS Version 2 Raster Page Device Dictionary</A></CAPTION>
<THEAD>
<TR>
	<TH>Bytes</TH>
	<TH>Type</TH>
	<TH>Description</TH>
	<TH>Values</TH>
</TR>
</THEAD>
<TBODY>
<TR>
	<TD>0-419</TD>
	<TD>Version 1 header data</TD>
	<TD>See Table 1</TD>
</TR>
<TR>
	<TD>420-423</TD>
	<TD>Unsigned Integer</TD>
	<TD>cupsNumColors</TD>
	<TD>1 to 6 colors</TD>
</TR>
<TR>
	<TD>424-427</TD>
	<TD>IEEE Single Precision</TD>
	<TD>cupsBorderlessScalingFactor</TD>
	<TD>0.0 or 1.0 or greater</TD>
</TR>
<TR>
	<TD>428-435</TD>
	<TD>IEEE Single Precision (2)</TD>
	<TD>cupsPageSize</TD>
	<TD>Width and length in points</TD>
</TR>
<TR>
	<TD>436-451</TD>
	<TD>IEEE Single Precision (4)</TD>
	<TD>cupsImagingBBox</TD>
	<TD>Four floating point numbers giving the left, bottom,
	right, and top positions of the page bounding box in
	points</TD>
</TR>
<TR>
	<TD>452-515</TD>
	<TD>Unsigned Integers (16)</TD>
	<TD>cupsInteger</TD>
	<TD>16 driver-defined integer values</TD>
</TR>
<TR>
	<TD>516-579</TD>
	<TD>IEEE Single Precision (16)</TD>
	<TD>cupsReal</TD>
	<TD>16 driver-defined floating point values</TD>
</TR>
<TR>
	<TD>580-1603</TD>
	<TD>C Strings (16x64)</TD>
	<TD>cupsString</TD>
	<TD>16 driver-defined strings</TD>
</TR>
<TR>
	<TD>1604-1667</TD>
	<TD>C String</TD>
	<TD>cupsMarkerType</TD>
	<TD>Ink/toner type string</TD>
</TR>
<TR>
	<TD>1668-1731</TD>
	<TD>C String</TD>
	<TD>cupsRenderingIntent</TD>
	<TD>Color rendering intent string</TD>
</TR>
<TR>
	<TD>1732-1795</TD>
	<TD>C String</TD>
	<TD>cupsPageSizeName</TD>
	<TD>Page size name/keyword string from PPD</TD>
</TR>
</TBODY>
</TABLE></DIV>

<H3><A NAME="COMPRESSION">Compressed Raster Data Format</A></H3>

<P>The version 2 raster data is compressed using a modified TIFF
packbits algorithm. Lines are grouped into an integral number of
color values based upon the <CODE>cupsColorOrder</CODE>
setting:</P>

<DIV CLASS="table"><TABLE SUMMARY="Color Value Sizes">
<CAPTION><A NAME="TABLE3">Table 3: Color Value Sizes</A></CAPTION>
<TR>
	<TH>cupsColorOrder</TH>
	<TH>Bytes per color value</TH>
</TR>
<TR>
	<TD>0 (chunky)</TD>
	<TD>(<CODE>cupsBitsPerPixel</CODE> + 7) / 8</TD>
</TR>
<TR>
	<TD>1 (banded)</TD>
	<TD>(<CODE>cupsBitsPerColor</CODE> + 7) / 8</TD>
</TR>
<TR>
	<TD>2 (planar)</TD>
	<TD>(<CODE>cupsBitsPerColor</CODE> + 7) / 8</TD>
</TR>
</TABLE></DIV>

<P>Each line of raster data begins with a repetition count from 1
to 256 that is encoded using a single byte of "count - 1".</P>

<P>After the repetition count, whole color values for that line
are run-length encoded using the TIFF packbits algorithm. 1 to
128 repeated colors are encoded using an initial byte of "count -
1" followed by the color value byte(s). 2 to 128 non-repeating
colors are encoded using an initial byte of "257 - count"
followed by the color value bytes.</P>

<H2 CLASS="title"><A NAME="V3">Version 3 Raster File Format</A></H2>

<P>A version 3 raster file begins with a 32-bit synchronization
word: 0x52615333 ("RaS3") for big-endian architectures and
0x33536152 ("3SaR") for little-endian architectures. The writer
of the raster file will use the native word order, and the reader
is responsible for detecting a reversed word order file and
swapping bytes as needed. The CUPS Imaging API raster functions
perform this function automatically.</P>

<P>Following the synchronization word are a series of raster
pages. Each page starts with a version 2 page device dictionary
header and is followed immediately by the uncompressed raster data
for that page.</P>

<H2 CLASS="title"><A NAME="ENCODING">Pixel Value Coding</A></H2>

<P>The following sections describe the encoding and decoding of
the color values in a CUPS raster file. In general, colors are
packed into the minimum number of bytes, with special
consideration provided for efficiency of encoding and access.
Multi-byte values are stored in the native byte order and
automatically swapped as needed when reading them using the CUPS
imaging API.</P>

<H3>CUPS_ORDER_CHUNKED</H3>

<P>The chunked order provides the pixel value packed in a single
place. Pixel values with 8 or more bits per color are stored as
an array of colors in order, e.g. for
<CODE>CUPS_CSPACE_RGB</CODE> you will see 8/16-bits of red, then
blue, then green, then red, green, blue, etc. Pixel values with
less than 8 bits per color are packed together as shown in Table
4. <I>Multi-byte pixel values are stored in the native word
order, just as for 16-bit color values.</I></P>

<DIV CLASS="table"><TABLE SUMMARY="Chunked Color Values">
<CAPTION><A NAME="TABLE4">Table 4: Chunked Color Values</A></CAPTION>
<THEAD>
<TR>
	<TH>Bits</TH>
	<TH>1-color</TH>
	<TH>3-color</TH>
	<TH>4-color</TH>
	<TH>6-color</TH>
</TR>
</THEAD>
<TBODY>
<TR>
	<TD>1</TD>
	<TD>W/W/W/W/W/W/W/W</TD>
	<TD>0RGB/0RGB</TD>
	<TD>CMYK/CMYK</TD>
	<TD>00KCMYcm</TD>
</TR>
<TR>
	<TD>2</TD>
	<TD>WW/WW/WW/WW</TD>
	<TD>00RRGGBB</TD>
	<TD>CCMMYYKK</TD>
	<TD>N/A</TD>
</TR>
<TR>
	<TD>4</TD>
	<TD>WWWW/WWWW</TD>
	<TD>0000RRRRGGGGBBBB<BR>
	<I>(multi-byte)</I></TD>
	<TD>CCCCMMMMYYYYKKKK<BR>
	<I>(multi-byte)</I></TD>
	<TD>N/A</TD>
</TR>
</TBODY>
</TABLE></DIV>

<H3>CUPS_ORDER_BANDED</H3>

<P>The banded order provides each color as a separate line of
data. Each color plane for a line is written in sequence, e.g.
for the <CODE>CUPS_CSPACE_CMYK</CODE> colorspace you would see
all of the cyan pixels for a line followed by the magenta,
yellow, and black pixels for that line. This is repeated for all
of the lines on the page. Color values are packed starting with
the most-significant bit (MSB) first.</P>

<H3>CUPS_ORDER_PLANAR</H3>

<P>The planar order provides each color as a separate page of
data using a shared page header. Each color plane for a page is
written in sequence, e.g. for the <CODE>CUPS_CSPACE_CMYK</CODE>
colorspace you would see all of the cyan pixels for a page
followed by the magenta, yellow, and black pixels for that page.
Color values are packed starting with the most-significant bit
(MSB) first. Each line starts on an 8-bit boundary.</P>

<H3>CUPS_CSPACE_W, CUPS_CSPACE_RGB, CUPS_CSPACE_RGBA, and
CUPS_CSPACE_RGBW</H3>

<P>These colorspaces use the sRGB colorspace definition and
whitepoint.</P>

<H3>CUPS_CSPACE_KCMYcm</H3>

<P>When <CODE>cupsBitsPerColor</CODE> is 1, 6 color planes are
provided - black, cyan, magenta, yellow, light cyan, and light
magenta. When <CODE>cupsBitsPerColor</CODE> is greater than 1, 4
color planes are provided using the <CODE>CUPS_CSPACE_KCMY</CODE>
colorspace instead.</P>

<P>When <CODE>cupsColorOrder</CODE> is
<CODE>CUPS_ORDER_CHUNKED</CODE>, bit 5 corresponds to black and
bit 0 corresponds to light magenta. For
<CODE>CUPS_ORDER_BANDED</CODE> and
<CODE>CUPS_ORDER_PLANAR</CODE>, each color plane is encoded
separately.</P>

<H3>CUPS_CSPACE_CIELab and CUPS_CSPACE_ICCn</H3>

<P>These colorspaces map a CIE Lab color value with a D65
whitepoint to either a 8- or 16-bit per color chunked
(<CODE>CUPS_ORDER_CHUNKED</CODE>) format; the banded
(<CODE>CUPS_ORDER_BANDED</CODE>) and planar
(<CODE>CUPS_ORDER_PLANAR</CODE>) color orders are not
supported.</P>

<P>The values are encoded and decoded using the following
formulas:</P>

<UL>

<LI>8-bit Encoding:<BR>
	<I>L8 = 2.55 * L + 0.5<BR>
	a8 = a + 128.5<BR>
	b8 = b + 128.5<BR>
	&nbsp;</I></LI>

<LI>8-bit Decoding:<BR>
	<I>L = L8 / 2.55<BR>
	a = a8 - 128<BR>
	b = b8 - 128<BR>
	&nbsp;</I></LI>

<LI>16-bit Encoding:<BR>
	<I>L16 = 655.35 * L + 0.5<BR>
	a16 = 256 * (a + 128) + 0.5<BR>
	b16 = 256 * (b + 128) + 0.5<BR>
	&nbsp;</I></LI>

<LI>16-bit Decoding:<BR>
	<I>L = L16 / 655.35<BR>
	a = a16 / 256 - 128<BR>
	b = b16 / 256 - 128<BR>
	&nbsp;</I></LI>

</UL>

<H3>CUPS_CSPACE_CIEXYZ</H3>

<P>These colorspaces map a CIE XYZ color value with a D65
whitepoint to either a 8- or 16-bit per color chunked
(<CODE>CUPS_ORDER_CHUNKED</CODE>) format; the banded
(<CODE>CUPS_ORDER_BANDED</CODE>) and planar
(<CODE>CUPS_ORDER_PLANAR</CODE>) color orders are not
supported.</P>

<P>The values are encoded and decoded using the following
formulas:</P>

<UL>

<LI>8-bit Encoding:<BR>
	<I>X8 = 231.8181 * X + 0.5<BR>
	Y8 = 231.8181 * Y + 0.5<BR>
	Z8 = 231.8181 * Z + 0.5<BR>
	&nbsp;</I></LI>

<LI>8-bit Decoding:<BR>
	<I>X = X8 / 231.8181<BR>
	Y = Y8 / 231.8181<BR>
	Z = Z8 / 231.8181<BR>
	&nbsp;</I></LI>

<LI>16-bit Encoding:<BR>
	<I>X16 = 59577.2727 * X + 0.5<BR>
	Y16 = 59577.2727 * Y + 0.5<BR>
	Z16 = 59577.2727 * Z + 0.5<BR>
	&nbsp;</I></LI>

<LI>16-bit Decoding:<BR>
	<I>X = X16 / 59577.2727<BR>
	Y = Y16 / 59577.2727<BR>
	Z = Z16 / 59577.2727<BR>
	&nbsp;</I></LI>

</UL>

<P>The scaling factor for XYZ values is 1/1.1, or 231.8181 for
8-bit values and 59577.2727 for 16-bit values. This allows for a
slight overflow of XYZ values when converting from RGB, improving
accuracy.</P>

<H2 CLASS="title"><A NAME="HISTORY">Change History</A></H2>

<H3>Changes in CUPS 1.2.2</H3>

<ul>

<li>Added version 3 (uncompressed) format.</li>

</ul>

<H3>Changes in CUPS 1.2.1</H3>

<ul>

<li>Added new sections on coding pixel values.</li>

<li>Clarified definitions of color spaces.</li>

</ul>

<H3>Changes in CUPS 1.2</H3>

<ul>

<li>Bumped raster version to 2</li>

<li>Added RGBW colorspace</li>

<li>Added 16 bit per color support</li>

<li>Added cupsNumColors, cupsBorderlessScalingFactor,
	cupsPageSize, cupsImagingBBox, cupsInteger, cupsReal,
	cupsString, cupsMarkerType, cupsRenderingIntent, and
	cupsPageSizeName attributes to the page device
	dictionary</li>

<li>Added raster data compression</li>

<li>Added data type column to device dictionary
	documentation.</li>

</ul>

<h3>Changes in CUPS 1.1.19</h3>

<ul>

<li>Added ICC and CIE colorspaces.</li>

</ul>

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