| <HTML> |
| <!-- SECTION: Specifications --> |
| <HEAD> |
| <TITLE>CUPS Raster Format</TITLE> |
| <LINK REL="STYLESHEET" TYPE="test/css" HREF="../cups.css"> |
| </HEAD> |
| <BODY> |
| |
| <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 |
| introduces a version 2 format that is a superset of the version 1 |
| format. Applications using the CUPS Imaging API (the cupsRaster* |
| functions) can read both 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="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> |
| </I></LI> |
| |
| <LI>8-bit Decoding:<BR> |
| <I>L = L8 / 2.55<BR> |
| a = a8 - 128<BR> |
| b = b8 - 128<BR> |
| </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> |
| </I></LI> |
| |
| <LI>16-bit Decoding:<BR> |
| <I>L = L16 / 655.35<BR> |
| a = a16 / 256 - 128<BR> |
| b = b16 / 256 - 128<BR> |
| </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> |
| </I></LI> |
| |
| <LI>8-bit Decoding:<BR> |
| <I>X = X8 / 231.8181<BR> |
| Y = Y8 / 231.8181<BR> |
| Z = Z8 / 231.8181<BR> |
| </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> |
| </I></LI> |
| |
| <LI>16-bit Decoding:<BR> |
| <I>X = X16 / 59577.2727<BR> |
| Y = Y16 / 59577.2727<BR> |
| Z = Z16 / 59577.2727<BR> |
| </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 1.2.1</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> |
| |
| </BODY> |
| </HTML> |
