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      1 <h2 class='title'><a name='BASICS'>Printer Driver Basics</a></h2>
      2 
      3 <p>A CUPS PostScript printer driver consists of a PostScript Printer Description (PPD) file that describes the features and capabilities of the device, zero or more <em>filter</em> programs that prepare print data for the device, and zero or more support files for color management, online help, and so forth. The PPD file includes references to all of the filters and support files used by the driver.</p>
      4 
      5 <p>Every time a user prints something the scheduler program, <a href='man-cupsd.html'>cupsd(8)</a>, determines the format of the print job and the programs required to convert that job into something the printer understands. CUPS includes filter programs for many common formats, for example to convert Portable Document Format (PDF) files into device-independent PostScript, and then from device-independent PostScript to device-dependent PostScript. <a href='#FIGURE_1'>Figure 1</a> shows the data flow of a typical print job.</p>
      6 
      7 <div class='figure'><table summary='PostScript Filter Chain'>
      8 <caption>Figure 1: <a name='FIGURE_1'>PostScript Filter Chain</a></caption>
      9 <tr><td><img src='../images/cups-postscript-chain.png' width='700' height='150' alt='PostScript Filter Chain'></td></tr>
     10 </table></div>
     11 
     12 <p>The optional PostScript filter can be provided to add printer-specific commands to the PostScript output that cannot be represented in the PPD file or to reorganize the output for special printer features. Typically this is used to support advanced job management or finishing functions on the printer. CUPS includes a generic PostScript filter that handles all PPD-defined commands.</p>
     13 
     14 <p>The optional port monitor handles interface-specific protocol or encoding issues. For example, many PostScript printers support the Binary Communications Protocol (BCP) and Tagged Binary Communications Protocol (TBCP) to allow applications to print 8-bit ("binary") PostScript jobs. CUPS includes port monitors for BCP and TBCP, and you can supply your own port monitors as needed.</p>
     15 
     16 <p>The backend handles communications with the printer, sending print data from the last filter to the printer and relaying back-channel data from the printer to the upstream filters. CUPS includes backend programs for common direct-connect interfaces and network protocols, and you can provide your own backend to support custom interfaces and protocols.</p>
     17 
     18 <p>The scheduler also supports a special "command" file format for sending maintenance commands and status queries to a printer or printer driver. Command print jobs typically use a single command filter program defined in the PPD file to generate the appropriate printer commands and handle any responses from the printer. <a href='#FIGURE_2'>Figure 2</a> shows the data flow of a typical command job.</p>
     19 
     20 <div class='figure'><table summary='Command Filter Chain'>
     21 <caption>Figure 2: <a name='FIGURE_2'>Command Filter Chain</a></caption>
     22 <tr><td><img src='../images/cups-command-chain.png' width='575' height='150' alt='Command Filter Chain'></td></tr>
     23 </table></div>
     24 
     25 <p>PostScript printer drivers typically do not require their own command filter since CUPS includes a generic PostScript command filter that supports all of the standard functions using PPD-defined commands.</p>
     26 
     27 
     28 <h2 class='title'><a name='CREATING'>Creating New PPD Files</a></h2>
     29 
     30 <p>We recommend using the CUPS PPD compiler, <a href='man-ppdc.html'>ppdc(1)</a>, to create new PPD files since it manages many of the tedious (and error-prone!) details of paper sizes and localization for you. It also allows you to easily support multiple devices from a single source file. For more information see the "<a href='ppd-compiler.html'>Introduction to the PPD Compiler</a>" document. <a href='#LISTING_1'>Listing 1</a> shows a driver information file for a black-and-white PostScript printer.</p>
     31 
     32 <p class='example'>Listing 1: <a name='LISTING_1'>"examples/postscript.drv"</a></p>
     33 
     34 <pre class='example'>
     35 // Include standard font and media definitions
     36 <a href='ref-ppdcfile.html#_include'>#include</a> &lt;font.defs&gt;
     37 <a href='ref-ppdcfile.html#_include'>#include</a> &lt;media.defs&gt;
     38 
     39 // Specify this is a PostScript printer driver
     40 <a href='ref-ppdcfile.html#DriverType'>DriverType</a> ps
     41 
     42 // List the fonts that are supported, in this case all standard fonts
     43 <a href='ref-ppdcfile.html#Font'>Font</a> *
     44 
     45 // Manufacturer, model name, and version
     46 <a href='ref-ppdcfile.html#Manufacturer'>Manufacturer</a> "Foo"
     47 <a href='ref-ppdcfile.html#ModelName'>ModelName</a> "Foo LaserProofer 2000"
     48 <a href='ref-ppdcfile.html#Version'>Version</a> 1.0
     49 
     50 // PostScript printer attributes
     51 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> DefaultColorSpace "" Gray
     52 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> LandscapeOrientation "" Minus90
     53 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> LanguageLevel "" "3"
     54 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> Product "" "(Foo LaserProofer 2000)"
     55 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> PSVersion "" "(3010) 0"
     56 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> TTRasterizer "" Type42
     57 
     58 // Supported page sizes
     59 *<a href='ref-ppdcfile.html#MediaSize'>MediaSize</a> Letter
     60 <a href='ref-ppdcfile.html#MediaSize'>MediaSize</a> Legal
     61 <a href='ref-ppdcfile.html#MediaSize'>MediaSize</a> A4
     62 
     63 // Query command for page size
     64 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> "?PageSize" "" "
     65       save
     66       currentpagedevice /PageSize get aload pop
     67       2 copy gt {exch} if (Unknown)
     68       23 dict
     69               dup [612 792] (Letter) put
     70               dup [612 1008] (Legal) put
     71               dup [595 842] (A4) put
     72               {exch aload pop 4 index sub abs 5 le exch
     73                5 index sub abs 5 le and
     74               {exch pop exit} {pop} ifelse
     75       } bind forall = flush pop pop
     76       restore"
     77 
     78 // Specify the name of the PPD file we want to generate
     79 <a href='ref-ppdcfile.html#PCFileName'>PCFileName</a> "fooproof.ppd"
     80 </pre>
     81 
     82 <h3>Required Attributes</h3>
     83 
     84 <p>PostScript drivers require the attributes listed in <a href='#TABLE_1'>Table 1</a>. If not specified, the defaults for CUPS drivers are used. A typical PostScript driver information file would include the following attributes:</p>
     85 
     86 <pre class='example'>
     87 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> DefaultColorSpace "" Gray
     88 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> LandscapeOrientation "" Minus90
     89 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> LanguageLevel "" "3"
     90 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> Product "" "(Foo LaserProofer 2000)"
     91 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> PSVersion "" "(3010) 0"
     92 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> TTRasterizer "" Type42
     93 </pre>
     94 
     95 <div class='table'><table summary='Required PostScript Printer Driver Attributes'>
     96 <caption>Table 1: <a name='TABLE_1'>Required PostScript Printer Driver Attributes</a></caption>
     97 <thead>
     98 <tr>
     99 	<th>Attribute</th>
    100 	<th>Description</th>
    101 </tr>
    102 </thead>
    103 <tbody>
    104 <tr>
    105 	<td><tt>DefaultColorSpace</tt></td>
    106 	<td>The default colorspace:
    107 	<tt>Gray</tt>, <tt>RGB</tt>, <tt>CMY</tt>, or
    108 	<tt>CMYK</tt>. If not specified, then <tt>RGB</tt> is
    109 	assumed.</td>
    110 </tr>
    111 <tr>
    112 	<td><tt>LandscapeOrientation</tt></td>
    113 	<td>The preferred landscape
    114 	orientation: <tt>Plus90</tt>, <tt>Minus90</tt>, or
    115 	<tt>Any</tt>. If not specified, <tt>Plus90</tt> is
    116 	assumed.</td>
    117 </tr>
    118 <tr>
    119 	<td><tt>LanguageLevel</tt></td>
    120 	<td>The PostScript language
    121 	level supported by the device: 1, 2, or 3. If not
    122 	specified, 2 is assumed.</td>
    123 </tr>
    124 <tr>
    125 	<td><tt>Product</tt></td>
    126 	<td>The string returned by
    127 	the PostScript <tt>product</tt> operator, which
    128 	<i>must</i> include parenthesis to conform with
    129 	PostScript syntax rules for strings. Multiple
    130 	<tt>Product</tt> attributes may be specified to support
    131 	multiple products with the same PPD file. If not
    132 	specified, "(ESP Ghostscript)" and "(GNU Ghostscript)"
    133 	are assumed.</td>
    134 </tr>
    135 <tr>
    136 	<td><tt>PSVersion</tt></td>
    137 	<td>The PostScript
    138 	interpreter version numbers as returned by the
    139 	<tt>version</tt> and <tt>revision</tt> operators. The
    140 	required format is "(version) revision". Multiple
    141 	<tt>PSVersion</tt> attributes may be specified to
    142 	support multiple interpreter version numbers. If not
    143 	specified, "(3010) 705" and "(3010) 707" are
    144 	assumed.</td>
    145 </tr>
    146 <tr>
    147 	<td><tt>TTRasterizer</tt></td>
    148 	<td>The type of TrueType
    149 	font rasterizer supported by the device, if any. The
    150 	supported values are <tt>None</tt>, <tt>Accept68k</tt>,
    151 	<tt>Type42</tt>, and <tt>TrueImage</tt>. If not
    152 	specified, <tt>None</tt> is assumed.</td>
    153 </tr>
    154 </table></div>
    155 
    156 <h3>Query Commands</h3>
    157 
    158 <p>Most PostScript printer PPD files include query commands (<tt>?PageSize</tt>, etc.) that allow applications to query the printer for its current settings and configuration. Query commands are included in driver information files as attributes. For example, the example in <a href='#LISTING_1'>Listing 1</a> uses the following definition for the <tt>PageSize</tt> query command:</p>
    159 
    160 <pre class='example'>
    161 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> "?PageSize" "" "
    162       save
    163       currentpagedevice /PageSize get aload pop
    164       2 copy gt {exch} if (Unknown)
    165       23 dict
    166               dup [612 792] (Letter) put
    167               dup [612 1008] (Legal) put
    168               dup [595 842] (A4) put
    169               {exch aload pop 4 index sub abs 5 le exch
    170                5 index sub abs 5 le and
    171               {exch pop exit} {pop} ifelse
    172       } bind forall = flush pop pop
    173       restore"
    174 </pre>
    175 
    176 <p>Query commands can span multiple lines, however no single line may contain more than 255 characters.</p>
    177 
    178 <h3><a name='IMPORT'>Importing Existing PPD Files</a></h3>
    179 
    180 <P>CUPS includes a utility called <a href='man-ppdi.html'>ppdi(1)</a>
    181 which allows you to import existing PPD files into the driver information file
    182 format used by the PPD compiler <a href='man-ppdc.html'>ppdc(1)</a>. Once
    183 imported, you can modify, localize, and regenerate the PPD files easily. Type
    184 the following command to import the PPD file <VAR>mydevice.ppd</VAR> into the
    185 driver information file <VAR>mydevice.drv</VAR>:</P>
    186 
    187 <pre class='command'>
    188 ppdi -o mydevice.drv mydevice.ppd
    189 </pre>
    190 
    191 <P>If you have a whole directory of PPD files that you would like to import,
    192 you can list multiple filenames or use shell wildcards to import more than one
    193 PPD file on the command-line:</P>
    194 
    195 <pre class='command'>
    196 ppdi -o mydevice.drv mydevice1.ppd mydevice2.ppd
    197 ppdi -o mydevice.drv *.ppd
    198 </pre>
    199 
    200 <P>If the driver information file already exists, the new PPD
    201 file entries are appended to the end of the file. Each PPD file
    202 is placed in its own group of curly braces within the driver
    203 information file.</P>
    204 
    205 
    206 <h2 class='title'><a name='FILTERS'>Using Custom Filters</a></h2>
    207 
    208 <p>Normally a PostScript printer driver will not utilize any additional print filters. For drivers that provide additional filters such as a CUPS command file filter for doing printer maintenance, you must also list the following <tt>Filter</tt> directive to handle printing PostScript files:</p>
    209 
    210 <pre class='example'>
    211 <a href='ref-ppdcfile.html#Filter'>Filter</a> application/vnd.cups-postscript 0 -
    212 </pre>
    213 
    214 <h3>Custom Command Filters</h3>
    215 
    216 <p>The <tt>application/vnd.cups-command</tt> file type is used for CUPS command files. Use the following <tt>Filter</tt> directive to handle CUPS command files:</p>
    217 
    218 <pre class='example'>
    219 <a href='ref-ppdcfile.html#Filter'>Filter</a> application/vnd.cups-command 100 /path/to/command/filter
    220 </pre>
    221 
    222 <p>To use the standard PostScript command filter, specify <var>commandtops</var> as the path to the command filter.</p>
    223 
    224 <h3>Custom PDF Filters</h3>
    225 
    226 <p>The <tt>application/pdf</tt> file type is used for unfiltered PDF files while the <tt>application/vnd.cups-pdf</tt> file type is used for filtered PDF files. Use the following <tt>Filter</tt> directive to handle filtered PDF files:</p>
    227 
    228 <pre class='example'>
    229 <a href='ref-ppdcfile.html#Filter'>Filter</a> application/vnd.cups-pdf 100 /path/to/pdf/filter
    230 </pre>
    231 
    232 <p>For unfiltered PDF files, use:</p>
    233 
    234 <pre class='example'>
    235 <a href='ref-ppdcfile.html#Filter'>Filter</a> application/pdf 100 /path/to/pdf/filter
    236 </pre>
    237 
    238 <p>Custom PDF filters that accept filtered data do not need to perform number-up processing and other types of page imposition, while those that accept unfiltered data MUST do the number-up processing themselves.</p>
    239 
    240 <h3>Custom PostScript Filters</h3>
    241 
    242 <p>The <tt>application/vnd.cups-postscript</tt> file type is used for filtered PostScript files. Use the following <tt>Filter</tt> directive to handle PostScript files:</p>
    243 
    244 <pre class='example'>
    245 <a href='ref-ppdcfile.html#Filter'>Filter</a> application/vnd.cups-postscript 100 /path/to/postscript/filter
    246 </pre>
    247 
    248 
    249 <h2 class='title'><a name='COLOR'>Implementing Color Management</a></h2>
    250 
    251 <p>CUPS uses ICC color profiles to provide more accurate color reproduction. The <a href='spec-ppd.html#cupsICCProfile'><tt>cupsICCProfile</tt></a> attribute defines the color profiles that are available for a given printer, for example:</p>
    252 
    253 <pre class='example'>
    254 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> cupsICCProfile "ColorModel.MediaType.Resolution/Description" /path/to/ICC/profile
    255 </pre>
    256 
    257 <p>where "ColorModel.MediaType.Resolution" defines a selector based on the corresponding option selections. A simple driver might only define profiles for the color models that are supported, for example a printer supporting Gray and RGB might use:</p>
    258 
    259 <pre class='example'>
    260 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> cupsICCProfile "Gray../Grayscale Profile" /path/to/ICC/gray-profile
    261 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> cupsICCProfile "RGB../Full Color Profile" /path/to/ICC/rgb-profile
    262 </pre>
    263 
    264 <p>The options used for profile selection can be customized using the <tt>cupsICCQualifier2</tt> and <tt>cupsICCQualifier3</tt> attributes.</p>
    265 
    266 
    267 <h2 class='title'><a name='MACOSX'>Adding macOS Features</a></h2>
    268 
    269 <p>macOS printer drivers can provide <a href='spec-ppd.html#MACOSX'>additional attributes</a> to specify additional option panes in the print dialog, an image of the printer, a help book, and option presets for the driver software:</p>
    270 
    271 <pre class='example'>
    272 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> APDialogExtension "" /Library/Printers/Vendor/filename.plugin
    273 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> APHelpBook "" /Library/Printers/Vendor/filename.bundle
    274 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> APPrinterIconPath "" /Library/Printers/Vendor/filename.icns
    275 <a href='ref-ppdcfile.html#Attribute'>Attribute</a> APPrinterPreset "name/text" "*option choice ..."
    276 </pre>
    277