1 <!-- 2 Raster API introduction for CUPS. 3 4 Copyright 2007-2013 by Apple Inc. 5 Copyright 1997-2006 by Easy Software Products, all rights reserved. 6 7 These coded instructions, statements, and computer programs are the 8 property of Apple Inc. and are protected by Federal copyright 9 law. Distribution and use rights are outlined in the file "LICENSE.txt" 10 which should have been included with this file. If this file is 11 file is missing or damaged, see the license at "http://www.cups.org/". 12 --> 13 14 <h2 class='title'><a name="OVERVIEW">Overview</a></h2> 15 16 <p>The CUPS raster API provides a standard interface for reading and writing 17 CUPS raster streams which are used for printing to raster printers. Because the 18 raster format is updated from time to time, it is important to use this API to 19 avoid incompatibilities with newer versions of CUPS.</p> 20 21 <p>Two kinds of CUPS filters use the CUPS raster API - raster image processor 22 (RIP) filters such as <code>pstoraster</code> and <code>cgpdftoraster</code> 23 (macOS) that produce CUPS raster files and printer driver filters that 24 convert CUPS raster files into a format usable by the printer. Printer 25 driver filters are by far the most common.</p> 26 27 <p>CUPS raster files (<code>application/vnd.cups-raster</code>) consists of 28 a stream of raster page descriptions produced by one of the RIP filters such as 29 <var>pstoraster</var>, <var>imagetoraster</var>, or 30 <var>cgpdftoraster</var>. CUPS raster files are referred to using the 31 <a href='#cups_raster_t'><code>cups_raster_t</code></a> type and are 32 opened using the <a href='#cupsRasterOpen'><code>cupsRasterOpen</code></a> 33 function. For example, to read raster data from the standard input, open 34 file descriptor 0:</p> 35 36 <pre class="example"> 37 #include <cups/raster.h> 38 39 <a href="#cups_raster_t">cups_raster_t</a> *ras = <a href="#cupsRasterOpen">cupsRasterOpen</a>(0, CUPS_RASTER_READ); 40 </pre> 41 42 <p>Each page of data begins with a page dictionary structure called 43 <a href="#cups_page_header2_t"><code>cups_page_header2_t</code></a>. This 44 structure contains the colorspace, bits per color, media size, media type, 45 hardware resolution, and so forth used for the page.</p> 46 47 <blockquote><b>Note:</b> 48 49 <p>Do not confuse the colorspace in the page header with the PPD 50 <tt>ColorModel</tt> keyword. <tt>ColorModel</tt> refers to the general type of 51 color used for a device (Gray, RGB, CMYK, DeviceN) and is often used to 52 select a particular colorspace for the page header along with the associate 53 color profile. The page header colorspace (<tt>cupsColorSpace</tt>) describes 54 both the type and organization of the color data, for example KCMY (black 55 first) instead of CMYK and RGBA (RGB + alpha) instead of RGB.</p> 56 57 </blockquote> 58 59 <p>You read the page header using the 60 <a href="#cupsRasterReadHeader2"><code>cupsRasterReadHeader2</code></a> 61 function:</p> 62 63 <pre class="example"> 64 #include <cups/raster.h> 65 66 <a href="#cups_raster_t">cups_raster_t</a> *ras = <a href="#cupsRasterOpen">cupsRasterOpen</a>(0, CUPS_RASTER_READ); 67 <a href="#cups_page_header2_t">cups_page_header2_t</a> header; 68 69 while (<a href="#cupsRasterReadHeader2">cupsRasterReadHeader2</a>(ras, &header)) 70 { 71 /* setup this page */ 72 73 /* read raster data */ 74 75 /* finish this page */ 76 } 77 </pre> 78 79 <p>After the page dictionary comes the page data which is a full-resolution, 80 possibly compressed bitmap representing the page in the printer's output 81 colorspace. You read uncompressed raster data using the 82 <a href="#cupsRasterReadPixels"><code>cupsRasterReadPixels</code></a> 83 function. A <code>for</code> loop is normally used to read the page one line 84 at a time:</p> 85 86 <pre class="example"> 87 #include <cups/raster.h> 88 89 <a href="#cups_raster_t">cups_raster_t</a> *ras = <a href="#cupsRasterOpen">cupsRasterOpen</a>(0, CUPS_RASTER_READ); 90 <a href="#cups_page_header2_t">cups_page_header2_t</a> header; 91 int page = 0; 92 int y; 93 char *buffer; 94 95 while (<a href="#cupsRasterReadHeader2">cupsRasterReadHeader2</a>(ras, &header)) 96 { 97 /* setup this page */ 98 page ++; 99 fprintf(stderr, "PAGE: %d %d\n", page, header.NumCopies); 100 101 /* allocate memory for 1 line */ 102 buffer = malloc(header.cupsBytesPerLine); 103 104 /* read raster data */ 105 for (y = 0; y < header.cupsHeight; y ++) 106 { 107 if (<a href="#cupsRasterReadPixels">cupsRasterReadPixels</a>(ras, buffer, header.cupsBytesPerLine) == 0) 108 break; 109 110 /* write raster data to printer on stdout */ 111 } 112 113 /* finish this page */ 114 } 115 </pre> 116 117 <p>When you are done reading the raster data, call the 118 <a href="#cupsRasterClose"><code>cupsRasterClose</code></a> function to free 119 the memory used to read the raster file:</p> 120 121 <pre class="example"> 122 <a href="#cups_raster_t">cups_raster_t</a> *ras; 123 124 <a href="#cupsRasterClose">cupsRasterClose</a>(ras); 125 </pre> 126 127 128 <h2 class='title'><a name="TASKS">Functions by Task</a></h2> 129 130 <h3><a name="OPENCLOSE">Opening and Closing Raster Streams</a></h3> 131 132 <ul class="code"> 133 134 <li><a href="#cupsRasterClose" title="Close a raster stream.">cupsRasterClose</a></li> 135 <li><a href="#cupsRasterOpen" title="Open a raster stream.">cupsRasterOpen</a></li> 136 137 </ul> 138 139 <h3><a name="READING">Reading Raster Streams</a></h3> 140 141 <ul class="code"> 142 143 <li><a href="#cupsRasterReadHeader" title="Read a raster page header and store it in a version 1 page header structure.">cupsRasterReadHeader</a> <span class="info">Deprecated in CUPS 1.2/macOS 10.5</span></li> 144 <li><a href="#cupsRasterReadHeader2" title="Read a raster page header and store it in a version 2 page header structure.">cupsRasterReadHeader2</a></li> 145 <li><a href="#cupsRasterReadPixels" title="Read raster pixels.">cupsRasterReadPixels</a></li> 146 147 </ul> 148 149 <h3><a name="WRITING">Writing Raster Streams</a></h3> 150 151 <ul class="code"> 152 153 <li><a href="#cupsRasterInterpretPPD" title="Interpret PPD commands to create a page header.">cupsRasterInterpretPPD</a></li> 154 <li><a href="#cupsRasterWriteHeader" title="Write a raster page header from a version 1 page header structure.">cupsRasterWriteHeader</a> <span class="info">Deprecated in CUPS 1.2/macOS 10.5</span></li> 155 <li><a href="#cupsRasterWriteHeader2" title="Write a raster page header from a version 2 page header structure.">cupsRasterWriteHeader2</a></li> 156 <li><a href="#cupsRasterWritePixels" title="Write raster pixels.">cupsRasterWritePixels</a></li> 157 158 </ul> 159
