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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="glGetTexImage"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glGetTexImage</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glGetTexImage</refname> | |
17 | <refpurpose>return a texture image</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glGetTexImage</function></funcdef> | |
23 | <paramdef>GLenum <parameter>target</parameter></paramdef> | |
24 | <paramdef>GLint <parameter>level</parameter></paramdef> | |
25 | <paramdef>GLenum <parameter>format</parameter></paramdef> | |
26 | <paramdef>GLenum <parameter>type</parameter></paramdef> | |
27 | <paramdef>GLvoid * <parameter>img</parameter></paramdef> | |
28 | </funcprototype> | |
29 | </funcsynopsis> | |
30 | </refsynopsisdiv> | |
31 | <!-- eqn: ignoring delim $$ --> | |
32 | <refsect1 id="parameters"><title>Parameters</title> | |
33 | <variablelist> | |
34 | <varlistentry> | |
35 | <term><parameter>target</parameter></term> | |
36 | <listitem> | |
37 | <para> | |
38 | Specifies which texture is to be obtained. | |
39 | <constant>GL_TEXTURE_1D</constant>, | |
40 | <constant>GL_TEXTURE_2D</constant>, | |
41 | <constant>GL_TEXTURE_3D</constant>, | |
42 | <constant>GL_TEXTURE_1D_ARRAY</constant>, | |
43 | <constant>GL_TEXTURE_2D_ARRAY</constant>, | |
44 | <constant>GL_TEXTURE_RECTANGLE</constant>, | |
45 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>, | |
46 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>, | |
47 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>, | |
48 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>, | |
49 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>, and | |
50 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant> | |
51 | are accepted. | |
52 | </para> | |
53 | </listitem> | |
54 | </varlistentry> | |
55 | <varlistentry> | |
56 | <term><parameter>level</parameter></term> | |
57 | <listitem> | |
58 | <para> | |
59 | Specifies the level-of-detail number of the desired image. | |
60 | Level 0 is the base image level. | |
61 | Level | |
62 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation> | |
63 | is the | |
64 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th | |
65 | mipmap reduction image. | |
66 | </para> | |
67 | </listitem> | |
68 | </varlistentry> | |
69 | <varlistentry> | |
70 | <term><parameter>format</parameter></term> | |
71 | <listitem> | |
72 | <para> | |
73 | Specifies a pixel format for the returned data. | |
74 | The supported formats are | |
75 | <constant>GL_STENCIL_INDEX</constant>, | |
76 | <constant>GL_DEPTH_COMPONENT</constant>, | |
77 | <constant>GL_DEPTH_STENCIL</constant>, | |
78 | <constant>GL_RED</constant>, | |
79 | <constant>GL_GREEN</constant>, | |
80 | <constant>GL_BLUE</constant>, | |
81 | <constant>GL_RG</constant>, | |
82 | <constant>GL_RGB</constant>, | |
83 | <constant>GL_RGBA</constant>, | |
84 | <constant>GL_BGR</constant>, | |
85 | <constant>GL_BGRA</constant>, | |
86 | <constant>GL_RED_INTEGER</constant>, | |
87 | <constant>GL_GREEN_INTEGER</constant>, | |
88 | <constant>GL_BLUE_INTEGER</constant>, | |
89 | <constant>GL_RG_INTEGER</constant>, | |
90 | <constant>GL_RGB_INTEGER</constant>, | |
91 | <constant>GL_RGBA_INTEGER</constant>, | |
92 | <constant>GL_BGR_INTEGER</constant>, | |
93 | <constant>GL_BGRA_INTEGER</constant>. | |
94 | </para> | |
95 | </listitem> | |
96 | </varlistentry> | |
97 | <varlistentry> | |
98 | <term><parameter>type</parameter></term> | |
99 | <listitem> | |
100 | <para> | |
101 | Specifies a pixel type for the returned data. | |
102 | The supported types are | |
103 | <constant>GL_UNSIGNED_BYTE</constant>, | |
104 | <constant>GL_BYTE</constant>, | |
105 | <constant>GL_UNSIGNED_SHORT</constant>, | |
106 | <constant>GL_SHORT</constant>, | |
107 | <constant>GL_UNSIGNED_INT</constant>, | |
108 | <constant>GL_INT</constant>, | |
109 | <constant>GL_HALF_FLOAT</constant>, | |
110 | <constant>GL_FLOAT</constant>, | |
111 | <constant>GL_UNSIGNED_BYTE_3_3_2</constant>, | |
112 | <constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>, | |
113 | <constant>GL_UNSIGNED_SHORT_5_6_5</constant>, | |
114 | <constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>, | |
115 | <constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>, | |
116 | <constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>, | |
117 | <constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>, | |
118 | <constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>, | |
119 | <constant>GL_UNSIGNED_INT_8_8_8_8</constant>, | |
120 | <constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>, | |
121 | <constant>GL_UNSIGNED_INT_10_10_10_2</constant>, | |
122 | <constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>, | |
123 | <constant>GL_UNSIGNED_INT_24_8</constant>, | |
124 | <constant>GL_UNSIGNED_INT_10F_11F_11F_REV</constant>, | |
125 | <constant>GL_UNSIGNED_INT_5_9_9_9_REV</constant>, and | |
126 | <constant>GL_FLOAT_32_UNSIGNED_INT_24_8_REV</constant>. | |
127 | </para> | |
128 | </listitem> | |
129 | </varlistentry> | |
130 | <varlistentry> | |
131 | <term><parameter>img</parameter></term> | |
132 | <listitem> | |
133 | <para> | |
134 | Returns the texture image. | |
135 | Should be a pointer to an array of the type specified by <parameter>type</parameter>. | |
136 | </para> | |
137 | </listitem> | |
138 | </varlistentry> | |
139 | </variablelist> | |
140 | </refsect1> | |
141 | <refsect1 id="description"><title>Description</title> | |
142 | <para> | |
143 | <function>glGetTexImage</function> returns a texture image into <parameter>img</parameter>. | |
144 | <parameter>target</parameter> specifies whether the desired texture image is one specified by | |
145 | <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry> (<constant>GL_TEXTURE_1D</constant>), | |
146 | <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry> (<constant>GL_TEXTURE_1D_ARRAY</constant>, <constant>GL_TEXTURE_RECTANGLE</constant>, | |
147 | <constant>GL_TEXTURE_2D</constant> or any of | |
148 | <constant>GL_TEXTURE_CUBE_MAP_*</constant>), | |
149 | or | |
150 | <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry> (<constant>GL_TEXTURE_2D_ARRAY</constant>, | |
151 | <constant>GL_TEXTURE_3D</constant>). | |
152 | <parameter>level</parameter> specifies the level-of-detail number of the desired image. | |
153 | <parameter>format</parameter> and <parameter>type</parameter> specify the format and type of the desired image array. | |
154 | See the reference page for <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry> | |
155 | for a description of the acceptable values for the <parameter>format</parameter> and <parameter>type</parameter> | |
156 | parameters, respectively. | |
157 | </para> | |
158 | <para> | |
159 | If a non-zero named buffer object is bound to the <constant>GL_PIXEL_PACK_BUFFER</constant> target | |
160 | (see <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>) while a texture image is | |
161 | requested, <parameter>img</parameter> is treated as a byte offset into the buffer object's data store. | |
162 | </para> | |
163 | <para> | |
164 | To understand the operation of <function>glGetTexImage</function>, consider the selected internal | |
165 | four-component texture image to be an RGBA color buffer the size of the image. | |
166 | The semantics of <function>glGetTexImage</function> are then identical to those of <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>, | |
167 | with the exception that no pixel transfer operations are performed, | |
168 | when called with the same <parameter>format</parameter> and <parameter>type</parameter>, | |
169 | with <emphasis>x</emphasis> and <emphasis>y</emphasis> set to 0, | |
170 | <emphasis>width</emphasis> set to the width of the texture image | |
171 | and <emphasis>height</emphasis> set to 1 for 1D images, | |
172 | or to the height of the texture image | |
173 | for 2D images. | |
174 | </para> | |
175 | <para> | |
176 | If the selected texture image does not contain four components, | |
177 | the following mappings are applied. | |
178 | Single-component textures are treated as RGBA buffers with red set | |
179 | to the single-component value, | |
180 | green set to 0, blue set to 0, and alpha set to 1. | |
181 | Two-component textures are treated as RGBA buffers with red set to | |
182 | the value of component zero, | |
183 | alpha set to the value of component one, | |
184 | and green and blue set to 0. | |
185 | Finally, | |
186 | three-component textures are treated as RGBA buffers with red set to | |
187 | component zero, | |
188 | green set to component one, | |
189 | blue set to component two, | |
190 | and alpha set to 1. | |
191 | </para> | |
192 | <para> | |
193 | To determine the required size of <parameter>img</parameter>, | |
194 | use <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> to determine the dimensions of the | |
195 | internal texture image, | |
196 | then scale the required number of pixels by the storage required for | |
197 | each pixel, | |
198 | based on <parameter>format</parameter> and <parameter>type</parameter>. | |
199 | Be sure to take the pixel storage parameters into account, | |
200 | especially <constant>GL_PACK_ALIGNMENT</constant>. | |
201 | </para> | |
202 | </refsect1> | |
203 | <refsect1 id="notes"><title>Notes</title> | |
204 | <para> | |
205 | If an error is generated, | |
206 | no change is made to the contents of <parameter>img</parameter>. | |
207 | </para> | |
208 | <para> | |
209 | <function>glGetTexImage</function> returns the texture image for the active texture unit. | |
210 | </para> | |
211 | </refsect1> | |
212 | <refsect1 id="errors"><title>Errors</title> | |
213 | <para> | |
214 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter>, <parameter>format</parameter>, or <parameter>type</parameter> is not | |
215 | an accepted value. | |
216 | </para> | |
217 | <para> | |
218 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>level</parameter> is less than 0. | |
219 | </para> | |
220 | <para> | |
221 | <constant>GL_INVALID_VALUE</constant> may be generated if <parameter>level</parameter> is greater | |
222 | than | |
223 | <inlineequation><mml:math> | |
224 | <!-- eqn: log sub 2 (max): --> | |
225 | <mml:mrow> | |
226 | <mml:msub><mml:mi mathvariant="italic">log</mml:mi> | |
227 | <mml:mn>2</mml:mn> | |
228 | </mml:msub> | |
229 | <mml:mo>⁡</mml:mo> | |
230 | <mml:mfenced open="(" close=")"> | |
231 | <mml:mi mathvariant="italic">max</mml:mi> | |
232 | </mml:mfenced> | |
233 | </mml:mrow> | |
234 | </mml:math></inlineequation>, | |
235 | where | |
236 | <inlineequation><mml:math><mml:mi mathvariant="italic">max</mml:mi></mml:math></inlineequation> | |
237 | is the returned value of <constant>GL_MAX_TEXTURE_SIZE</constant>. | |
238 | </para> | |
239 | <para> | |
240 | <constant>GL_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is one of | |
241 | <constant>GL_UNSIGNED_BYTE_3_3_2</constant>, | |
242 | <constant>GL_UNSIGNED_BYTE_2_3_3_REV</constant>, | |
243 | <constant>GL_UNSIGNED_SHORT_5_6_5</constant>, | |
244 | <constant>GL_UNSIGNED_SHORT_5_6_5_REV</constant>, or | |
245 | <constant>GL_UNSIGNED_INT_10F_11F_11F_REV</constant> and <parameter>format</parameter> is not <constant>GL_RGB</constant>. | |
246 | </para> | |
247 | <para> | |
248 | <constant>GL_INVALID_OPERATION</constant> is returned if <parameter>type</parameter> is one of | |
249 | <constant>GL_UNSIGNED_SHORT_4_4_4_4</constant>, | |
250 | <constant>GL_UNSIGNED_SHORT_4_4_4_4_REV</constant>, | |
251 | <constant>GL_UNSIGNED_SHORT_5_5_5_1</constant>, | |
252 | <constant>GL_UNSIGNED_SHORT_1_5_5_5_REV</constant>, | |
253 | <constant>GL_UNSIGNED_INT_8_8_8_8</constant>, | |
254 | <constant>GL_UNSIGNED_INT_8_8_8_8_REV</constant>, | |
255 | <constant>GL_UNSIGNED_INT_10_10_10_2</constant>, | |
256 | <constant>GL_UNSIGNED_INT_2_10_10_10_REV</constant>, or | |
257 | <constant>GL_UNSIGNED_INT_5_9_9_9_REV</constant> and <parameter>format</parameter> is neither <constant>GL_RGBA</constant> | |
258 | or <constant>GL_BGRA</constant>. | |
259 | </para> | |
260 | <para> | |
261 | <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the | |
262 | <constant>GL_PIXEL_PACK_BUFFER</constant> target and the buffer object's data store is currently mapped. | |
263 | </para> | |
264 | <para> | |
265 | <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the | |
266 | <constant>GL_PIXEL_PACK_BUFFER</constant> target and the data would be packed to the buffer | |
267 | object such that the memory writes required would exceed the data store size. | |
268 | </para> | |
269 | <para> | |
270 | <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to the | |
271 | <constant>GL_PIXEL_PACK_BUFFER</constant> target and <parameter>img</parameter> is not evenly divisible | |
272 | into the number of bytes needed to store in memory a datum indicated by <parameter>type</parameter>. | |
273 | </para> | |
274 | </refsect1> | |
275 | <refsect1 id="associatedgets"><title>Associated Gets</title> | |
276 | <para> | |
277 | <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_WIDTH</constant> | |
278 | </para> | |
279 | <para> | |
280 | <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_HEIGHT</constant> | |
281 | </para> | |
282 | <para> | |
283 | <citerefentry><refentrytitle>glGetTexLevelParameter</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_INTERNAL_FORMAT</constant> | |
284 | </para> | |
285 | <para> | |
286 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with arguments <constant>GL_PACK_ALIGNMENT</constant> and others | |
287 | </para> | |
288 | <para> | |
289 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_PIXEL_PACK_BUFFER_BINDING</constant> | |
290 | </para> | |
291 | </refsect1> | |
292 | <refsect1 id="seealso"><title>See Also</title> | |
293 | <para> | |
294 | <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>, | |
295 | <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>, | |
296 | <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>, | |
297 | <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, | |
298 | <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>, | |
299 | <citerefentry><refentrytitle>glTexSubImage1D</refentrytitle></citerefentry>, | |
300 | <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>, | |
301 | <citerefentry><refentrytitle>glTexSubImage3D</refentrytitle></citerefentry>, | |
302 | <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry> | |
303 | </para> | |
304 | </refsect1> | |
305 | <refsect1 id="Copyright"><title>Copyright</title> | |
306 | <para> | |
307 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
308 | Silicon Graphics, Inc. Copyright <trademark class="copyright"></trademark> 2010 | |
309 | Khronos Group. This document is licensed under the SGI | |
310 | Free Software B License. For details, see | |
311 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
312 | </para> | |
313 | </refsect1> | |
314 | </refentry> |