| 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> |