Commit | Line | Data |
---|---|---|
7faf1d71 AW |
1 | <?xml version="1.0" encoding="UTF-8"?> |
2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd"> | |
4 | <refentry id="glGetCompressedTexImage"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glGetCompressedTexImage</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glGetCompressedTexImage</refname> | |
17 | <refpurpose>return a compressed texture image</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glGetCompressedTexImage</function></funcdef> | |
23 | <paramdef>GLenum <parameter>target</parameter></paramdef> | |
24 | <paramdef>GLint <parameter>lod</parameter></paramdef> | |
25 | <paramdef>GLvoid * <parameter>img</parameter></paramdef> | |
26 | </funcprototype> | |
27 | </funcsynopsis> | |
28 | </refsynopsisdiv> | |
29 | <!-- eqn: ignoring delim $$ --> | |
30 | <refsect1 id="parameters"><title>Parameters</title> | |
31 | <variablelist> | |
32 | <varlistentry> | |
33 | <term><parameter>target</parameter></term> | |
34 | <listitem> | |
35 | <para> | |
36 | Specifies which texture is to be obtained. | |
37 | <constant>GL_TEXTURE_1D</constant>, <constant>GL_TEXTURE_2D</constant>, <constant>GL_TEXTURE_3D</constant>, | |
38 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>, | |
39 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>, | |
40 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>, | |
41 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>, | |
42 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>, and | |
43 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant> | |
44 | are accepted. | |
45 | </para> | |
46 | </listitem> | |
47 | </varlistentry> | |
48 | <varlistentry> | |
49 | <term><parameter>lod</parameter></term> | |
50 | <listitem> | |
51 | <para> | |
52 | Specifies the level-of-detail number of the desired image. | |
53 | Level 0 is the base image level. | |
54 | Level | |
55 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation> | |
56 | is the | |
57 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th | |
58 | mipmap reduction image. | |
59 | </para> | |
60 | </listitem> | |
61 | </varlistentry> | |
62 | <varlistentry> | |
63 | <term><parameter>img</parameter></term> | |
64 | <listitem> | |
65 | <para> | |
66 | Returns the compressed texture image. | |
67 | </para> | |
68 | </listitem> | |
69 | </varlistentry> | |
70 | </variablelist> | |
71 | </refsect1> | |
72 | <refsect1 id="description"><title>Description</title> | |
73 | <para> | |
74 | <function>glGetCompressedTexImage</function> returns the compressed texture image associated with <parameter>target</parameter> and <parameter>lod</parameter> | |
75 | into <parameter>img</parameter>. <parameter>img</parameter> should be an array of | |
76 | <constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant> bytes. | |
77 | <parameter>target</parameter> specifies whether the desired texture image was one specified by | |
78 | <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry> (<constant>GL_TEXTURE_1D</constant>), | |
79 | <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry> (<constant>GL_TEXTURE_2D</constant> or any of <constant>GL_TEXTURE_CUBE_MAP_*</constant>), or | |
80 | <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry> (<constant>GL_TEXTURE_3D</constant>). | |
81 | <parameter>lod</parameter> specifies the level-of-detail number of the desired image. | |
82 | </para> | |
83 | <para> | |
84 | If a non-zero named buffer object is bound to the <constant>GL_PIXEL_PACK_BUFFER</constant> target | |
85 | (see <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>) while a texture image is | |
86 | requested, <parameter>img</parameter> is treated as a byte offset into the buffer object's data store. | |
87 | </para> | |
88 | <para> | |
89 | To minimize errors, first verify that the texture is compressed by calling | |
90 | <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_COMPRESSED</constant>. If | |
91 | the texture is compressed, then determine the amount of memory required to | |
92 | store the compressed texture by calling <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with | |
93 | argument <constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant>. Finally, retrieve the | |
94 | internal format of the texture by calling <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with | |
95 | argument <constant>GL_TEXTURE_INTERNAL_FORMAT</constant>. | |
96 | To store the texture for later use, associate the internal format and size | |
97 | with the retrieved texture image. These data can be used by the respective | |
98 | texture or subtexture loading routine used for loading <parameter>target</parameter> textures. | |
99 | </para> | |
100 | </refsect1> | |
101 | <refsect1 id="errors"><title>Errors</title> | |
102 | <para> | |
103 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>lod</parameter> is less than zero or greater | |
104 | than the maximum number of LODs permitted by the implementation. | |
105 | </para> | |
106 | <para> | |
107 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glGetCompressedTexImage</function> is used to retrieve a | |
108 | texture that is in an uncompressed internal format. | |
109 | </para> | |
110 | <para> | |
111 | <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the | |
112 | <constant>GL_PIXEL_PACK_BUFFER</constant> target and the buffer object's data store is currently mapped. | |
113 | </para> | |
114 | <para> | |
115 | <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the | |
116 | <constant>GL_PIXEL_PACK_BUFFER</constant> target and the data would be packed to the buffer | |
117 | object such that the memory writes required would exceed the data store size. | |
118 | </para> | |
119 | </refsect1> | |
120 | <refsect1 id="associatedgets"><title>Associated Gets</title> | |
121 | <para> | |
122 | <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_COMPRESSED</constant> | |
123 | </para> | |
124 | <para> | |
125 | <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant> | |
126 | </para> | |
127 | <para> | |
128 | <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_INTERNAL_FORMAT</constant> | |
129 | </para> | |
130 | <para> | |
131 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_PIXEL_PACK_BUFFER_BINDING</constant> | |
132 | </para> | |
133 | </refsect1> | |
134 | <refsect1 id="seealso"><title>See Also</title> | |
135 | <para> | |
136 | <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>, | |
137 | <citerefentry><refentrytitle>glCompressedTexImage1D</refentrytitle></citerefentry>, | |
138 | <citerefentry><refentrytitle>glCompressedTexImage2D</refentrytitle></citerefentry>, | |
139 | <citerefentry><refentrytitle>glCompressedTexImage3D</refentrytitle></citerefentry>, | |
140 | <citerefentry><refentrytitle>glCompressedTexSubImage1D</refentrytitle></citerefentry>, | |
141 | <citerefentry><refentrytitle>glCompressedTexSubImage2D</refentrytitle></citerefentry>, | |
142 | <citerefentry><refentrytitle>glCompressedTexSubImage3D</refentrytitle></citerefentry>, | |
143 | <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>, | |
144 | <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>, | |
145 | <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, | |
146 | <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>, | |
147 | <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry>, | |
148 | <citerefentry><refentrytitle>glTexSubImage1D</refentrytitle></citerefentry>, | |
149 | <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>, | |
150 | <citerefentry><refentrytitle>glTexSubImage3D</refentrytitle></citerefentry> | |
151 | </para> | |
152 | </refsect1> | |
153 | <refsect1 id="Copyright"><title>Copyright</title> | |
154 | <para> | |
155 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
156 | Silicon Graphics, Inc. This document is licensed under the SGI | |
157 | Free Software B License. For details, see | |
158 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
159 | </para> | |
160 | </refsect1> | |
161 | </refentry> |