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b423cd4c | 1 | <!-- |
eac3a0a0 | 2 | Raster API introduction for CUPS. |
b423cd4c | 3 | |
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4 | Copyright © 2007-2013 by Apple Inc. |
5 | Copyright © 1997-2006 by Easy Software Products, all rights reserved. | |
b423cd4c | 6 | |
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7 | Licensed under Apache License v2.0. See the file "LICENSE" for more |
8 | information. | |
b423cd4c | 9 | --> |
10 | ||
5a738aea | 11 | <h2 class='title'><a name="OVERVIEW">Overview</a></h2> |
b423cd4c | 12 | |
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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> | |
b423cd4c | 17 | |
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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> | |
8072030b | 20 | (macOS) that produce CUPS raster files and printer driver filters that |
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21 | convert CUPS raster files into a format usable by the printer. Printer |
22 | driver filters are by far the most common.</p> | |
23 | ||
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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> | |
b423cd4c | 32 | |
5a738aea | 33 | <pre class="example"> |
8b3724f8 | 34 | #include <cups/raster.h> |
b423cd4c | 35 | |
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36 | <a href="#cups_raster_t">cups_raster_t</a> *ras = <a href="#cupsRasterOpen">cupsRasterOpen</a>(0, CUPS_RASTER_READ); |
37 | </pre> | |
38 | ||
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, | |
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42 | hardware resolution, and so forth used for the page.</p> |
43 | ||
44 | <blockquote><b>Note:</b> | |
45 | ||
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> | |
53 | ||
54 | </blockquote> | |
55 | ||
56 | <p>You read the page header using the | |
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57 | <a href="#cupsRasterReadHeader2"><code>cupsRasterReadHeader2</code></a> |
58 | function:</p> | |
59 | ||
60 | <pre class="example"> | |
8b3724f8 | 61 | #include <cups/raster.h> |
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62 | |
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; | |
b423cd4c | 65 | |
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66 | while (<a href="#cupsRasterReadHeader2">cupsRasterReadHeader2</a>(ras, &header)) |
67 | { | |
68 | /* setup this page */ | |
69 | ||
70 | /* read raster data */ | |
71 | ||
72 | /* finish this page */ | |
73 | } | |
b423cd4c | 74 | </pre> |
75 | ||
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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 | |
81 | at a time:</p> | |
82 | ||
83 | <pre class="example"> | |
8b3724f8 | 84 | #include <cups/raster.h> |
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85 | |
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; | |
88 | int page = 0; | |
89 | int y; | |
90 | char *buffer; | |
b423cd4c | 91 | |
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92 | while (<a href="#cupsRasterReadHeader2">cupsRasterReadHeader2</a>(ras, &header)) |
93 | { | |
94 | /* setup this page */ | |
95 | page ++; | |
96 | fprintf(stderr, "PAGE: %d %d\n", page, header.NumCopies); | |
b423cd4c | 97 | |
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98 | /* allocate memory for 1 line */ |
99 | buffer = malloc(header.cupsBytesPerLine); | |
b423cd4c | 100 | |
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101 | /* read raster data */ |
102 | for (y = 0; y < header.cupsHeight; y ++) | |
103 | { | |
104 | if (<a href="#cupsRasterReadPixels">cupsRasterReadPixels</a>(ras, buffer, header.cupsBytesPerLine) == 0) | |
105 | break; | |
106 | ||
db0bd74a | 107 | /* write raster data to printer on stdout */ |
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108 | } |
109 | ||
110 | /* finish this page */ | |
111 | } | |
112 | </pre> | |
113 | ||
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> | |
117 | ||
118 | <pre class="example"> | |
119 | <a href="#cups_raster_t">cups_raster_t</a> *ras; | |
120 | ||
121 | <a href="#cupsRasterClose">cupsRasterClose</a>(ras); | |
122 | </pre> | |
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123 | |
124 | ||
125 | <h2 class='title'><a name="TASKS">Functions by Task</a></h2> | |
126 | ||
127 | <h3><a name="OPENCLOSE">Opening and Closing Raster Streams</a></h3> | |
128 | ||
129 | <ul class="code"> | |
130 | ||
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> | |
133 | ||
134 | </ul> | |
135 | ||
136 | <h3><a name="READING">Reading Raster Streams</a></h3> | |
137 | ||
138 | <ul class="code"> | |
139 | ||
8072030b | 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> |
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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> | |
143 | ||
144 | </ul> | |
145 | ||
146 | <h3><a name="WRITING">Writing Raster Streams</a></h3> | |
147 | ||
148 | <ul class="code"> | |
149 | ||
150 | <li><a href="#cupsRasterInterpretPPD" title="Interpret PPD commands to create a page header.">cupsRasterInterpretPPD</a></li> | |
8072030b | 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> |
75bd9771 | 152 | <li><a href="#cupsRasterWriteHeader2" title="Write a raster page header from a version 2 page header structure.">cupsRasterWriteHeader2</a></li> |
db0bd74a | 153 | <li><a href="#cupsRasterWritePixels" title="Write raster pixels.">cupsRasterWritePixels</a></li> |
f3c17241 | 154 | |
db0bd74a | 155 | </ul> |