doc/help/spec-raster.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
   2 <HTML>
   3 <!-- SECTION: Specifications -->
   4 <HEAD>
   5         <TITLE>CUPS Raster Format</TITLE>
   6         <LINK REL="STYLESHEET" TYPE="text/css" HREF="../cups-printable.css">
   7 </HEAD>
   8 <BODY>
   9
  10 <H1 CLASS="title">CUPS Raster Format</H1>
  11
  12 <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>
  13
  14 <P>CUPS 1.0 and 1.1 used version 1 of the raster format. CUPS 1.2 and later use version 2 (compressed) and version 3 (uncompressed) that are a superset of the version 1 raster format. All three versions of CUPS Raster are streamable formats, and applications using the CUPS Imaging API (the cupsRaster* functions) can read all formats without code changes.</P>
  15
  16 <P>The registered MIME media type for CUPS Raster files is <CODE>application/vnd.cups-raster</CODE>.</P>
  17
  18
  19 <H2 CLASS="title"><A NAME="ORGANIZATION">Organization of a CUPS Raster File</A></H2>
  20
  21 <P><A HREF="FILEFORMAT">Figure 1, "Raster Organization"</A>, shows the general organization of all CUPS Raster files. Each file begins with a 32-bit synchronization word followed by zero or more pages. Each page consists of a  header (the PostScript page device dictionary and raster-specific values) followed by the bitmap image for the page.</P>
  22
  23 <DIV CLASS="figure"><TABLE SUMMARY="Raster Organization">
  24 <CAPTION><A NAME="FILEFORMAT">Figure 1: Raster Organization</A></CAPTION>
  25 <TR><TD><IMG SRC="../images/raster-organization.png" WIDTH="446" HEIGHT="1056" ALT="Raster Organization"></TD></TR>
  26 </TABLE></DIV>
  27
  28 <P>Each page bitmap is stored as described by the <CODE>cupsBitsPerColor</CODE>, <CODE>cupsBytesPerLine</CODE>, <CODE>cupsColorOrder</CODE>, <CODE>cupsColorSpace</CODE>, <CODE>cupsHeight</CODE>, and <CODE>cupsWidth</CODE> values in the page header. Pixels for the front side of a sheet are always stored left-to-right, top-to-bottom. When doing duplex printing, pixels for the back side of a sheet may be stored differently depending on the value of the <CODE>cupsBackSide</CODE> keyword ("Normal", "ManualTumble", "Rotated", or "Flipped") in the PPD file and the <CODE>Tumble</CODE> value ("true" or "false") in the page header. <A HREF="#PAGEBITMAPS">Figure 2, "Page Bitmaps"</A>, shows the pixel order for each combination.</P>
  29
  30 <DIV CLASS="figure"><TABLE SUMMARY="Page Bitmaps">
  31 <CAPTION><A NAME="PAGEBITMAPS">Figure 2: Page Bitmaps</A></CAPTION>
  32 <TR><TD><IMG SRC="../images/raster.png" WIDTH="624" HEIGHT="448" ALT="Page Bitmaps"></TD></TR>
  33 </TABLE></DIV>
  34
  35
  36 <H2 CLASS="title"><A NAME="V1">Version 1 Raster File Format</A></H2>
  37
  38 <P>A version 1 raster file begins with a 32-bit synchronization word: 0x52615374 ("RaSt") for big-endian architectures or 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>
  39
  40 <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>
  41
  42 <DIV CLASS="table"><TABLE SUMMARY="CUPS Version 1 Raster Page Device Dictionary">
  43 <CAPTION><A NAME="TABLE1">Table 1: CUPS Version 1 Raster Page Device Dictionary</A></CAPTION>
  44 <THEAD>
  45 <TR>
  46         <TH>Bytes</TH>
  47         <TH>Type</TH>
  48         <TH>Description</TH>
  49         <TH>Values</TH>
  50 </TR>
  51 </THEAD>
  52 <TBODY>
  53 <TR>
  54         <TD>0-63</TD>
  55         <TD>C String</TD>
  56         <TD>MediaClass</TD>
  57         <TD>Media class string</TD>
  58 </TR>
  59 <TR>
  60         <TD>64-127</TD>
  61         <TD>C String</TD>
  62         <TD>MediaColor</TD>
  63         <TD>Media color string</TD>
  64 </TR>
  65 <TR>
  66         <TD>128-191</TD>
  67         <TD>C String</TD>
  68         <TD>MediaType</TD>
  69         <TD>Media type string</TD>
  70 </TR>
  71 <TR>
  72         <TD>192-255</TD>
  73         <TD>C String</TD>
  74         <TD>OutputType</TD>
  75         <TD>Output type string</TD>
  76 </TR>
  77 <TR>
  78         <TD>256-259</TD>
  79         <TD>Unsigned Integer</TD>
  80         <TD>AdvanceDistance</TD>
  81         <TD>0 to 2<SUP>32</SUP> - 1 points</TD>
  82 </TR>
  83 <TR>
  84         <TD>260-263</TD>
  85         <TD>Unsigned Integer</TD>
  86         <TD>AdvanceMedia</TD>
  87         <TD>0 = Never advance roll<BR>
  88         1 = Advance roll after file<BR>
  89         2 = Advance roll after job<BR>
  90         3 = Advance roll after set<BR>
  91         4 = Advance roll after page</TD>
  92 </TR>
  93 <TR>
  94         <TD>264-267</TD>
  95         <TD>Unsigned Integer</TD>
  96         <TD>Collate</TD>
  97         <TD>0 = do not collate copies<BR>
  98         1 = collate copies</TD>
  99 </TR>
 100 <TR>
 101         <TD>268-271</TD>
 102         <TD>Unsigned Integer</TD>
 103         <TD>CutMedia</TD>
 104         <TD>0 = Never cut media<BR>
 105         1 = Cut roll after file<BR>
 106         2 = Cut roll after job<BR>
 107         3 = Cut roll after set<BR>
 108         4 = Cut roll after page</TD>
 109 </TR>
 110 <TR>
 111         <TD>272-275</TD>
 112         <TD>Unsigned Integer</TD>
 113         <TD>Duplex</TD>
 114         <TD>0 = Print single-sided<BR>
 115         1 = Print double-sided</TD>
 116 </TR>
 117 <TR>
 118         <TD>276-283</TD>
 119         <TD>Unsigned Integers (2)</TD>
 120         <TD>HWResolution</TD>
 121         <TD>Horizontal and vertical resolution in dots-per-inch.</TD>
 122 </TR>
 123 <TR>
 124         <TD>284-299</TD>
 125         <TD>Unsigned Integers (4)</TD>
 126         <TD>ImagingBoundingBox</TD>
 127         <TD>Four integers giving the left, bottom, right, and top positions
 128         of the page bounding box in points</TD>
 129 </TR>
 130 <TR>
 131         <TD>300-303</TD>
 132         <TD>Unsigned Integer</TD>
 133         <TD>InsertSheet</TD>
 134         <TD>0 = Do not insert separator sheets<BR>
 135         1 = Insert separator sheets</TD>
 136 </TR>
 137 <TR>
 138         <TD>304-307</TD>
 139         <TD>Unsigned Integer</TD>
 140         <TD>Jog</TD>
 141         <TD>0 = Do no jog pages<BR>
 142         1 = Jog pages after file<BR>
 143         2 = Jog pages after job<BR>
 144         3 = Jog pages after set</TD>
 145 </TR>
 146 <TR>
 147         <TD>308-311</TD>
 148         <TD>Unsigned Integer</TD>
 149         <TD>LeadingEdge</TD>
 150         <TD>0 = Top edge is first<BR>
 151         1 = Right edge is first<BR>
 152         2 = Bottom edge is first<BR>
 153         3 = Left edge is first</TD>
 154 </TR>
 155 <TR>
 156         <TD>312-319</TD>
 157         <TD>Unsigned Integers (2)</TD>
 158         <TD>Margins</TD>
 159         <TD>Left and bottom origin of image in points</TD>
 160 </TR>
 161 <TR>
 162         <TD>320-323</TD>
 163         <TD>Unsigned Integer</TD>
 164         <TD>ManualFeed</TD>
 165         <TD>0 = Do not manually feed media<BR>
 166         1 = Manually feed media</TD>
 167 </TR>
 168 <TR>
 169         <TD>324-327</TD>
 170         <TD>Unsigned Integer</TD>
 171         <TD>MediaPosition</TD>
 172         <TD>Input slot position from 0 to N</TD>
 173 </TR>
 174 <TR>
 175         <TD>328-331</TD>
 176         <TD>Unsigned Integer</TD>
 177         <TD>MediaWeight</TD>
 178         <TD>Media weight in grams per meter squared, 0 = printer default</TD>
 179 </TR>
 180 <TR>
 181         <TD>332-335</TD>
 182         <TD>Unsigned Integer</TD>
 183         <TD>MirrorPrint</TD>
 184         <TD>0 = Do not mirror prints<BR>
 185         1 = Mirror prints</TD>
 186 </TR>
 187 <TR>
 188         <TD>336-339</TD>
 189         <TD>Unsigned Integer</TD>
 190         <TD>NegativePrint</TD>
 191         <TD>0 = Do not invert prints<BR>
 192         1 = Invert prints</TD>
 193 </TR>
 194 <TR>
 195         <TD>340-343</TD>
 196         <TD>Unsigned Integer</TD>
 197         <TD>NumCopies</TD>
 198         <TD>0 to 2<SUP>32</SUP> - 1, 0 = printer default</TD>
 199 </TR>
 200 <TR>
 201         <TD>344-347</TD>
 202         <TD>Unsigned Integer</TD>
 203         <TD>Orientation</TD>
 204         <TD>0 = Do not rotate page<BR>
 205         1 = Rotate page counter-clockwise<BR>
 206         2 = Turn page upside down<BR>
 207         3 = Rotate page clockwise</TD>
 208 </TR>
 209 <TR>
 210         <TD>348-351</TD>
 211         <TD>Unsigned Integer</TD>
 212         <TD>OutputFaceUp</TD>
 213         <TD>0 = Output face down<BR>
 214         1 = Output face up</TD>
 215 </TR>
 216 <TR>
 217         <TD>352-359</TD>
 218         <TD>Unsigned Integers (2)</TD>
 219         <TD>PageSize</TD>
 220         <TD>Width and length in points</TD>
 221 </TR>
 222 <TR>
 223         <TD>360-363</TD>
 224         <TD>Unsigned Integer</TD>
 225         <TD>Separations</TD>
 226         <TD>0 = Print composite image<BR>
 227         1 = Print color separations</TD>
 228 </TR>
 229 <TR>
 230         <TD>364-367</TD>
 231         <TD>Unsigned Integer</TD>
 232         <TD>TraySwitch</TD>
 233         <TD>0 = Do not change trays if selected tray is empty<BR>
 234         1 = Change trays if selected tray is empty</TD>
 235 </TR>
 236 <TR>
 237         <TD>368-371</TD>
 238         <TD>Unsigned Integer</TD>
 239         <TD>Tumble</TD>
 240         <TD>0 = Do not rotate even pages when duplexing<BR>
 241         1 = Rotate even pages when duplexing</TD>
 242 </TR>
 243 <TR>
 244         <TD>372-375</TD>
 245         <TD>Unsigned Integer</TD>
 246         <TD>cupsWidth</TD>
 247         <TD>Width of page image in pixels</TD>
 248 </TR>
 249 <TR>
 250         <TD>376-379</TD>
 251         <TD>Unsigned Integer</TD>
 252         <TD>cupsHeight</TD>
 253         <TD>Height of page image in pixels</TD>
 254 </TR>
 255 <TR>
 256         <TD>380-383</TD>
 257         <TD>Unsigned Integer</TD>
 258         <TD>cupsMediaType</TD>
 259         <TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
 260 </TR>
 261 <TR>
 262         <TD>384-387</TD>
 263         <TD>Unsigned Integer</TD>
 264         <TD>cupsBitsPerColor</TD>
 265         <TD>1, 2, 4, 8 bits for version 1 raster files<BR>
 266         1, 2, 4, 8, and 16 bits for version 2/3 raster files</TD>
 267 </TR>
 268 <TR>
 269         <TD>388-391</TD>
 270         <TD>Unsigned Integer</TD>
 271         <TD>cupsBitsPerPixel</TD>
 272         <TD>1 to 32 bits for version 1 raster files<BR>
 273         1 to 240 bits for version 2/3 raster files</TD>
 274 </TR>
 275 <TR>
 276         <TD>392-395</TD>
 277         <TD>Unsigned Integer</TD>
 278         <TD>cupsBytesPerLine</TD>
 279         <TD>1 to 2<SUP>32</SUP> - 1 bytes</TD>
 280 </TR>
 281 <TR>
 282         <TD>396-399</TD>
 283         <TD>Unsigned Integer</TD>
 284         <TD>cupsColorOrder</TD>
 285         <TD>0 = chunky pixels (CMYK CMYK CMYK)<BR>
 286         1 = banded pixels (CCC MMM YYY KKK)<BR>
 287         2 = planar pixels (CCC... MMM... YYY... KKK...)</TD>
 288 </TR>
 289 <TR>
 290         <TD>400-403</TD>
 291         <TD>Unsigned Integer</TD>
 292         <TD>cupsColorSpace</TD>
 293         <TD>0 = gray (device, typically sRGB-based)<BR>
 294         1 = RGB (device, typically sRGB)<BR>
 295         2 = RGBA (device, typically sRGB)<BR>
 296         3 = black<BR>
 297         4 = CMY<BR>
 298         5 = YMC<BR>
 299         6 = CMYK<BR>
 300         7 = YMCK<BR>
 301         8 = KCMY<BR>
 302         9 = KCMYcm<BR>
 303         10 = GMCK<BR>
 304         11 = GMCS<BR>
 305         12 = WHITE<BR>
 306         13 = GOLD<BR>
 307         14 = SILVER<BR>
 308         15 = CIE XYZ<BR>
 309         16 = CIE Lab<BR>
 310         17 = RGBW (sRGB)<BR>
 311         18 = sGray (gray using sRGB gamma/white point)<BR>
 312         19 = sRGB<BR>
 313         20 = AdobeRGB<BR>
 314         32 = ICC1 (CIE Lab with hint for 1 color)<BR>
 315         33 = ICC2 (CIE Lab with hint for 2 colors)<BR>
 316         34 = ICC3 (CIE Lab with hint for 3 colors)<BR>
 317         35 = ICC4 (CIE Lab with hint for 4 colors)<BR>
 318         36 = ICC5 (CIE Lab with hint for 5 colors)<BR>
 319         37 = ICC6 (CIE Lab with hint for 6 colors)<BR>
 320         38 = ICC7 (CIE Lab with hint for 7 colors)<BR>
 321         39 = ICC8 (CIE Lab with hint for 8 colors)<BR>
 322         40 = ICC9 (CIE Lab with hint for 9 colors)<BR>
 323         41 = ICCA (CIE Lab with hint for 10 colors)<BR>
 324         42 = ICCB (CIE Lab with hint for 11 colors)<BR>
 325         43 = ICCC (CIE Lab with hint for 12 colors)<BR>
 326         44 = ICCD (CIE Lab with hint for 13 colors)<BR>
 327         45 = ICCE (CIE Lab with hint for 14 colors)<BR>
 328         46 = ICCF (CIE Lab with hint for 15 colors)<BR>
 329         48 = Device1 (DeviceN for 1 color)<BR>
 330         49 = Device2 (DeviceN for 2 colors)<BR>
 331         50 = Device3 (DeviceN for 3 colors)<BR>
 332         51 = Device4 (DeviceN for 4 colors)<BR>
 333         52 = Device5 (DeviceN for 5 colors)<BR>
 334         53 = Device6 (DeviceN for 6 colors)<BR>
 335         54 = Device7 (DeviceN for 7 colors)<BR>
 336         55 = Device8 (DeviceN for 8 colors)<BR>
 337         56 = Device9 (DeviceN for 9 colors)<BR>
 338         57 = DeviceA (DeviceN for 10 colors)<BR>
 339         58 = DeviceB (DeviceN for 11 colors)<BR>
 340         59 = DeviceC (DeviceN for 12 colors)<BR>
 341         60 = DeviceD (DeviceN for 13 colors)<BR>
 342         61 = DeviceE (DeviceN for 14 colors)<BR>
 343         62 = DeviceF (DeviceN for 15 colors)
 344         </TD>
 345 </TR>
 346 <TR>
 347         <TD>404-407</TD>
 348         <TD>Unsigned Integer</TD>
 349         <TD>cupsCompression</TD>
 350         <TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
 351 </TR>
 352 <TR>
 353         <TD>408-411</TD>
 354         <TD>Unsigned Integer</TD>
 355         <TD>cupsRowCount</TD>
 356         <TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
 357 </TR>
 358 <TR>
 359         <TD>412-415</TD>
 360         <TD>Unsigned Integer</TD>
 361         <TD>cupsRowFeed</TD>
 362         <TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
 363 </TR>
 364 <TR>
 365         <TD>416-419</TD>
 366         <TD>Unsigned Integer</TD>
 367         <TD>cupsRowStep</TD>
 368         <TD>Driver-specific 0 to 2<SUP>32</SUP> - 1</TD>
 369 </TR>
 370 </TBODY>
 371 </TABLE></DIV>
 372
 373
 374 <H2 CLASS="title"><A NAME="V2">Version 2 Raster File Format</A></H2>
 375
 376 <P>A version 2 raster file begins with a 32-bit synchronization word: 0x52615332 ("RaS2") for big-endian architectures or 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>
 377
 378 <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>
 379
 380 <DIV CLASS="table"><TABLE SUMMARY="CUPS Version 2 Raster Page Device Dictionary">
 381 <CAPTION><A NAME="TABLE2">Table 2: CUPS Version 2 Raster Page Device Dictionary</A></CAPTION>
 382 <THEAD>
 383 <TR>
 384         <TH>Bytes</TH>
 385         <TH>Type</TH>
 386         <TH>Description</TH>
 387         <TH>Values</TH>
 388 </TR>
 389 </THEAD>
 390 <TBODY>
 391 <TR>
 392         <TD>0-419</TD>
 393         <TD>Version 1 header data</TD>
 394         <TD>See Table 1</TD>
 395 </TR>
 396 <TR>
 397         <TD>420-423</TD>
 398         <TD>Unsigned Integer</TD>
 399         <TD>cupsNumColors</TD>
 400         <TD>1 to 15 colors</TD>
 401 </TR>
 402 <TR>
 403         <TD>424-427</TD>
 404         <TD>IEEE Single Precision</TD>
 405         <TD>cupsBorderlessScalingFactor</TD>
 406         <TD>0.0 or 1.0 or greater</TD>
 407 </TR>
 408 <TR>
 409         <TD>428-435</TD>
 410         <TD>IEEE Single Precision (2)</TD>
 411         <TD>cupsPageSize</TD>
 412         <TD>Width and length in points</TD>
 413 </TR>
 414 <TR>
 415         <TD>436-451</TD>
 416         <TD>IEEE Single Precision (4)</TD>
 417         <TD>cupsImagingBBox</TD>
 418         <TD>Four floating point numbers giving the left, bottom, right, and top positions of the page bounding box in points</TD>
 419 </TR>
 420 <TR>
 421         <TD>452-515</TD>
 422         <TD>Unsigned Integers (16)</TD>
 423         <TD>cupsInteger</TD>
 424         <TD>16 driver-defined integer values</TD>
 425 </TR>
 426 <TR>
 427         <TD>516-579</TD>
 428         <TD>IEEE Single Precision (16)</TD>
 429         <TD>cupsReal</TD>
 430         <TD>16 driver-defined floating point values</TD>
 431 </TR>
 432 <TR>
 433         <TD>580-1603</TD>
 434         <TD>C Strings (16x64)</TD>
 435         <TD>cupsString</TD>
 436         <TD>16 driver-defined strings</TD>
 437 </TR>
 438 <TR>
 439         <TD>1604-1667</TD>
 440         <TD>C String</TD>
 441         <TD>cupsMarkerType</TD>
 442         <TD>Ink/toner type string</TD>
 443 </TR>
 444 <TR>
 445         <TD>1668-1731</TD>
 446         <TD>C String</TD>
 447         <TD>cupsRenderingIntent</TD>
 448         <TD>Color rendering intent string</TD>
 449 </TR>
 450 <TR>
 451         <TD>1732-1795</TD>
 452         <TD>C String</TD>
 453         <TD>cupsPageSizeName</TD>
 454         <TD>Page size name/keyword string from PPD</TD>
 455 </TR>
 456 </TBODY>
 457 </TABLE></DIV>
 458
 459 <H3><A NAME="COMPRESSION">Compressed Raster Data Format</A></H3>
 460
 461 <P>The version 2 raster data is compressed using a PackBits-like algorithm. Lines are grouped into an integral number of color values based upon the <CODE>cupsColorOrder</CODE> setting:</P>
 462
 463 <DIV CLASS="table"><TABLE SUMMARY="Color Value Sizes">
 464 <CAPTION><A NAME="TABLE3">Table 3: Color Value Sizes</A></CAPTION>
 465 <TR>
 466         <TH>cupsColorOrder</TH>
 467         <TH>Bytes per color value</TH>
 468 </TR>
 469 <TR>
 470         <TD>0 (chunky)</TD>
 471         <TD>(<CODE>cupsBitsPerPixel</CODE> + 7) / 8</TD>
 472 </TR>
 473 <TR>
 474         <TD>1 (banded)</TD>
 475         <TD>(<CODE>cupsBitsPerColor</CODE> + 7) / 8</TD>
 476 </TR>
 477 <TR>
 478         <TD>2 (planar)</TD>
 479         <TD>(<CODE>cupsBitsPerColor</CODE> + 7) / 8</TD>
 480 </TR>
 481 </TABLE></DIV>
 482
 483 <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>
 484
 485 <P>After the repetition count, whole color values for that line are run-length encoded using a PackBits-like run-length encoding algorithm: 1 to 128 repeated colors are encoded using an initial byte of "count - 1" followed by the color value byte(s) while 2 to 128 non-repeating colors are encoded using an initial byte of "257 - count" followed by the color value bytes.</P>
 486
 487 <P>For example, the 8x8 24-bit sRGB image shown in <a href="#SAMPLEIMAGE">Figure 3, "Sample Image"</a>, would be encoded as the following 89 octets:</p>
 488
 489 <PRE CLASS="example">
 490 %x00 %x00.FF.FF.FF %x02.FF.FF.00 %x03.FF.FF.FF
 491 %x00 %xFE.FF.FF.00.00.00.FF.FF.FF.00 %x02.FF.FF.FF %x00.00.FF.00 %x00.FF.FF.FF
 492 %x00 %x01.FF.FF.00 %x02.FF.FF.FF %x02.00.FF.00
 493 %x00 %x02.FF.FF.00 %x02.FF.FF.FF %x00.00.FF.00 %x00.FF.FF.FF
 494 %x00 %x00.FF.FF.FF %x02.FF.FF.00 %x03.FF.FF.FF
 495 %x00 %x07.FF.FF.FF
 496 %x01 %x07.FF.00.00
 497 </PRE>
 498
 499 <P>The first line (%x00) contains 1 white pixel (%x00.FF.FF.FF), 3 yellow pixels (%x02.FF.FF.00), and 4 white pixels (%x03.FF.FF.FF).</P>
 500
 501 <P>The second line (%x00) contains a sequence of yellow + blue + yellow pixels (%xFE.FF.FF.00.00.00.FF.FF.FF.00), 3 white pixels (%x02.FF.FF.FF), 1 green pixel (%x00.00.FF.00), and 1 white pixel (%x00.FF.FF.FF).</P>
 502
 503 <P>The third line (%x00) contains 2 yellow pixels (%x01.FF.FF.00), 3 white pixels (%x02.FF.FF.FF), and 3 green pixels (%x02.00.FF.00)</P>
 504
 505 <P>The fourth line (%x00) contains 3 yellow pixels (%x02.FF.FF.00), 3 white pixels (%x02.FF.FF.FF), 1 green pixel (%x00.00.FF.00), and 1 white pixel (%x00.FF.FF.FF).</P>
 506
 507 <P>The fifth line (%x00) contains 1 white pixel (%x00.FF.FF.FF), 3 yellow pixels (%x02.FF.FF.00), and 4 white pixels (%x03.FF.FF.FF).</P>
 508
 509 <P>The sixth line (%x00) contains 8 white pixels (%x07.FF.FF.FF).</P>
 510
 511 <P>The seventh and eighth lines (%x01) contain 8 red pixels (%x07.FF.00.00).</P>
 512
 513 <DIV CLASS="figure"><TABLE SUMMARY="Sample Image">
 514 <CAPTION><A NAME="SAMPLEIMAGE">Figure 3: Sample Image</A></CAPTION>
 515 <TR><TD><IMG SRC="../images/sample-image.png" WIDTH="257" HEIGHT="257" ALT="Sample Image"></TD></TR>
 516 </TABLE></DIV>
 517
 518
 519 <H2 CLASS="title"><A NAME="V3">Version 3 Raster File Format</A></H2>
 520
 521 <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>
 522
 523 <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/raw raster data for that page.</P>
 524
 525
 526 <H2 CLASS="title"><A NAME="ENCODING">Pixel Value Coding</A></H2>
 527
 528 <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>
 529
 530 <H3>CUPS_ORDER_CHUNKED</H3>
 531
 532 <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>
 533
 534 <DIV CLASS="table"><TABLE SUMMARY="Chunked Color Values">
 535 <CAPTION><A NAME="TABLE4">Table 4: Chunked Color Values</A></CAPTION>
 536 <THEAD>
 537 <TR>
 538         <TH>Bits</TH>
 539         <TH>1-color</TH>
 540         <TH>3-color</TH>
 541         <TH>4-color</TH>
 542         <TH>6-color</TH>
 543 </TR>
 544 </THEAD>
 545 <TBODY>
 546 <TR>
 547         <TD>1</TD>
 548         <TD>W/W/W/W/W/W/W/W</TD>
 549         <TD>0RGB/0RGB</TD>
 550         <TD>CMYK/CMYK</TD>
 551         <TD>00KCMYcm</TD>
 552 </TR>
 553 <TR>
 554         <TD>2</TD>
 555         <TD>WW/WW/WW/WW</TD>
 556         <TD>00RRGGBB</TD>
 557         <TD>CCMMYYKK</TD>
 558         <TD>N/A</TD>
 559 </TR>
 560 <TR>
 561         <TD>4</TD>
 562         <TD>WWWW/WWWW</TD>
 563         <TD>0000RRRRGGGGBBBB<BR>
 564         <I>(multi-byte)</I></TD>
 565         <TD>CCCCMMMMYYYYKKKK<BR>
 566         <I>(multi-byte)</I></TD>
 567         <TD>N/A</TD>
 568 </TR>
 569 </TBODY>
 570 </TABLE></DIV>
 571
 572 <H3>CUPS_ORDER_BANDED</H3>
 573
 574 <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> color space 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>
 575
 576 <H3>CUPS_ORDER_PLANAR</H3>
 577
 578 <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> color space 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>
 579
 580 <H3>CUPS_CSPACE_RGBW</H3>
 581
 582 <P>This color space provides a dedicated black text channel and uses the sRGB color space definition and white point for the RGB color channels. The white channel is 0 for text (or "true") black, otherwise it must contain the maximum color value: 1 for 1-bit, 3 for 2-bit, 15 for 4-bit, 255 for 8-bit, or 65535 for 16-bit.</P>
 583
 584 <H3>CUPS_CSPACE_KCMYcm</H3>
 585
 586 <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> color space instead.</P>
 587
 588 <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>
 589
 590 <H3>CUPS_CSPACE_CIELab and CUPS_CSPACE_ICCn</H3>
 591
 592 <P>These color spaces map a CIE Lab color value with a D65 white point 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>
 593
 594 <P>The values are encoded and decoded using the following formulas:</P>
 595
 596 <UL>
 597
 598         <LI>8-bit Encoding:<BR>
 599         <I>L8 = 2.55 * L + 0.5<BR>
 600         a8 = a + 128.5<BR>
 601         b8 = b + 128.5<BR>
 602         &nbsp;</I></LI>
 603
 604         <LI>8-bit Decoding:<BR>
 605         <I>L = L8 / 2.55<BR>
 606         a = a8 - 128<BR>
 607         b = b8 - 128<BR>
 608         &nbsp;</I></LI>
 609
 610         <LI>16-bit Encoding:<BR>
 611         <I>L16 = 655.35 * L + 0.5<BR>
 612         a16 = 256 * (a + 128) + 0.5<BR>
 613         b16 = 256 * (b + 128) + 0.5<BR>
 614         &nbsp;</I></LI>
 615
 616         <LI>16-bit Decoding:<BR>
 617         <I>L = L16 / 655.35<BR>
 618         a = a16 / 256 - 128<BR>
 619         b = b16 / 256 - 128<BR>
 620         &nbsp;</I></LI>
 621
 622 </UL>
 623
 624 <H3>CUPS_CSPACE_CIEXYZ</H3>
 625
 626 <P>These color spaces map a CIE XYZ color value with a D65 white point 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>
 627
 628 <P>The values are encoded and decoded using the following formulas:</P>
 629
 630 <UL>
 631
 632         <LI>8-bit Encoding:<BR>
 633         <I>X8 = 231.8181 * X + 0.5<BR>
 634         Y8 = 231.8181 * Y + 0.5<BR>
 635         Z8 = 231.8181 * Z + 0.5<BR>
 636         &nbsp;</I></LI>
 637
 638         <LI>8-bit Decoding:<BR>
 639         <I>X = X8 / 231.8181<BR>
 640         Y = Y8 / 231.8181<BR>
 641         Z = Z8 / 231.8181<BR>
 642         &nbsp;</I></LI>
 643
 644         <LI>16-bit Encoding:<BR>
 645         <I>X16 = 59577.2727 * X + 0.5<BR>
 646         Y16 = 59577.2727 * Y + 0.5<BR>
 647         Z16 = 59577.2727 * Z + 0.5<BR>
 648         &nbsp;</I></LI>
 649
 650         <LI>16-bit Decoding:<BR>
 651         <I>X = X16 / 59577.2727<BR>
 652         Y = Y16 / 59577.2727<BR>
 653         Z = Z16 / 59577.2727<BR>
 654         &nbsp;</I></LI>
 655
 656 </UL>
 657
 658 <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>
 659
 660
 661 <H2 CLASS="title"><A NAME="HISTORY">Change History</A></H2>
 662
 663 <H3>Changes in CUPS 1.4.7</H3>
 664
 665 <ul>
 666
 667         <li>Greatly improved the detail and now include an example of the bitmap compression.</li>
 668         <li>Added all missing cupsColorSpace values and a separate description of CUPS_CSPACE_RGBW.</li>
 669
 670 </ul>
 671
 672
 673 <H3>Changes in CUPS 1.2.2</H3>
 674
 675 <ul>
 676
 677         <li>Added version 3 (uncompressed) format.</li>
 678
 679 </ul>
 680
 681
 682 <H3>Changes in CUPS 1.2.1</H3>
 683
 684 <ul>
 685
 686         <li>Added new sections on coding pixel values.</li>
 687
 688         <li>Clarified definitions of color spaces.</li>
 689
 690 </ul>
 691
 692
 693 <H3>Changes in CUPS 1.2</H3>
 694
 695 <ul>
 696
 697         <li>Bumped raster version to 2</li>
 698
 699         <li>Added RGBW color space</li>
 700
 701         <li>Added 16 bit per color support</li>
 702
 703         <li>Added cupsNumColors, cupsBorderlessScalingFactor, cupsPageSize, cupsImagingBBox, cupsInteger, cupsReal, cupsString, cupsMarkerType, cupsRenderingIntent, and cupsPageSizeName attributes to the page device dictionary</li>
 704
 705         <li>Added raster data compression</li>
 706
 707         <li>Added data type column to device dictionary documentation.</li>
 708
 709 </ul>
 710
 711 <h3>Changes in CUPS 1.1.19</h3>
 712
 713 <ul>
 714
 715         <li>Added ICC and CIE color spaces.</li>
 716
 717 </ul>
 718
 719 </BODY>
 720 </HTML>