2 Raster API introduction for CUPS.
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5 Copyright © 1997-2006 by Easy Software Products, all rights reserved.
7 Licensed under Apache License v2.0. See the file "LICENSE" for more
11 <h2 class='title'><a name="OVERVIEW">Overview</a></h2>
13 <p>The CUPS raster API provides a standard interface for reading and writing
14 CUPS raster streams which are used for printing to raster printers. Because the
15 raster format is updated from time to time, it is important to use this API to
16 avoid incompatibilities with newer versions of CUPS.</p>
18 <p>Two kinds of CUPS filters use the CUPS raster API - raster image processor
19 (RIP) filters such as <code>pstoraster</code> and <code>cgpdftoraster</code>
20 (macOS) that produce CUPS raster files and printer driver filters that
21 convert CUPS raster files into a format usable by the printer. Printer
22 driver filters are by far the most common.</p>
24 <p>CUPS raster files (<code>application/vnd.cups-raster</code>) consists of
25 a stream of raster page descriptions produced by one of the RIP filters such as
26 <var>pstoraster</var>, <var>imagetoraster</var>, or
27 <var>cgpdftoraster</var>. CUPS raster files are referred to using the
28 <a href='#cups_raster_t'><code>cups_raster_t</code></a> type and are
29 opened using the <a href='#cupsRasterOpen'><code>cupsRasterOpen</code></a>
30 function. For example, to read raster data from the standard input, open
31 file descriptor 0:</p>
34 #include <cups/raster.h>
36 <a href="#cups_raster_t">cups_raster_t</a> *ras = <a href="#cupsRasterOpen">cupsRasterOpen</a>(0, CUPS_RASTER_READ);
39 <p>Each page of data begins with a page dictionary structure called
40 <a href="#cups_page_header2_t"><code>cups_page_header2_t</code></a>. This
41 structure contains the colorspace, bits per color, media size, media type,
42 hardware resolution, and so forth used for the page.</p>
44 <blockquote><b>Note:</b>
46 <p>Do not confuse the colorspace in the page header with the PPD
47 <tt>ColorModel</tt> keyword. <tt>ColorModel</tt> refers to the general type of
48 color used for a device (Gray, RGB, CMYK, DeviceN) and is often used to
49 select a particular colorspace for the page header along with the associate
50 color profile. The page header colorspace (<tt>cupsColorSpace</tt>) describes
51 both the type and organization of the color data, for example KCMY (black
52 first) instead of CMYK and RGBA (RGB + alpha) instead of RGB.</p>
56 <p>You read the page header using the
57 <a href="#cupsRasterReadHeader2"><code>cupsRasterReadHeader2</code></a>
61 #include <cups/raster.h>
63 <a href="#cups_raster_t">cups_raster_t</a> *ras = <a href="#cupsRasterOpen">cupsRasterOpen</a>(0, CUPS_RASTER_READ);
64 <a href="#cups_page_header2_t">cups_page_header2_t</a> header;
66 while (<a href="#cupsRasterReadHeader2">cupsRasterReadHeader2</a>(ras, &header))
70 /* read raster data */
72 /* finish this page */
76 <p>After the page dictionary comes the page data which is a full-resolution,
77 possibly compressed bitmap representing the page in the printer's output
78 colorspace. You read uncompressed raster data using the
79 <a href="#cupsRasterReadPixels"><code>cupsRasterReadPixels</code></a>
80 function. A <code>for</code> loop is normally used to read the page one line
84 #include <cups/raster.h>
86 <a href="#cups_raster_t">cups_raster_t</a> *ras = <a href="#cupsRasterOpen">cupsRasterOpen</a>(0, CUPS_RASTER_READ);
87 <a href="#cups_page_header2_t">cups_page_header2_t</a> header;
92 while (<a href="#cupsRasterReadHeader2">cupsRasterReadHeader2</a>(ras, &header))
96 fprintf(stderr, "PAGE: %d %d\n", page, header.NumCopies);
98 /* allocate memory for 1 line */
99 buffer = malloc(header.cupsBytesPerLine);
101 /* read raster data */
102 for (y = 0; y < header.cupsHeight; y ++)
104 if (<a href="#cupsRasterReadPixels">cupsRasterReadPixels</a>(ras, buffer, header.cupsBytesPerLine) == 0)
107 /* write raster data to printer on stdout */
110 /* finish this page */
114 <p>When you are done reading the raster data, call the
115 <a href="#cupsRasterClose"><code>cupsRasterClose</code></a> function to free
116 the memory used to read the raster file:</p>
118 <pre class="example">
119 <a href="#cups_raster_t">cups_raster_t</a> *ras;
121 <a href="#cupsRasterClose">cupsRasterClose</a>(ras);
125 <h2 class='title'><a name="TASKS">Functions by Task</a></h2>
127 <h3><a name="OPENCLOSE">Opening and Closing Raster Streams</a></h3>
131 <li><a href="#cupsRasterClose" title="Close a raster stream.">cupsRasterClose</a></li>
132 <li><a href="#cupsRasterOpen" title="Open a raster stream.">cupsRasterOpen</a></li>
136 <h3><a name="READING">Reading Raster Streams</a></h3>
140 <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>
141 <li><a href="#cupsRasterReadHeader2" title="Read a raster page header and store it in a version 2 page header structure.">cupsRasterReadHeader2</a></li>
142 <li><a href="#cupsRasterReadPixels" title="Read raster pixels.">cupsRasterReadPixels</a></li>
146 <h3><a name="WRITING">Writing Raster Streams</a></h3>
150 <li><a href="#cupsRasterInitPWGHeader" title="Interpret IPP attributes to create a page header.">cupsRasterInitPWGHeader</a></li>
151 <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>
152 <li><a href="#cupsRasterWriteHeader2" title="Write a raster page header from a version 2 page header structure.">cupsRasterWriteHeader2</a></li>
153 <li><a href="#cupsRasterWritePixels" title="Write raster pixels.">cupsRasterWritePixels</a></li>