| 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="glCopyConvolutionFilter2D"> |
| 5 | <refmeta> |
| 6 | <refmetainfo> |
| 7 | <copyright> |
| 8 | <year>1991-2006</year> |
| 9 | <holder>Silicon Graphics, Inc.</holder> |
| 10 | </copyright> |
| 11 | </refmetainfo> |
| 12 | <refentrytitle>glCopyConvolutionFilter2D</refentrytitle> |
| 13 | <manvolnum>3G</manvolnum> |
| 14 | </refmeta> |
| 15 | <refnamediv> |
| 16 | <refname>glCopyConvolutionFilter2D</refname> |
| 17 | <refpurpose>copy pixels into a two-dimensional convolution filter</refpurpose> |
| 18 | </refnamediv> |
| 19 | <refsynopsisdiv><title>C Specification</title> |
| 20 | <funcsynopsis> |
| 21 | <funcprototype> |
| 22 | <funcdef>void <function>glCopyConvolutionFilter2D</function></funcdef> |
| 23 | <paramdef>GLenum <parameter>target</parameter></paramdef> |
| 24 | <paramdef>GLenum <parameter>internalformat</parameter></paramdef> |
| 25 | <paramdef>GLint <parameter>x</parameter></paramdef> |
| 26 | <paramdef>GLint <parameter>y</parameter></paramdef> |
| 27 | <paramdef>GLsizei <parameter>width</parameter></paramdef> |
| 28 | <paramdef>GLsizei <parameter>height</parameter></paramdef> |
| 29 | </funcprototype> |
| 30 | </funcsynopsis> |
| 31 | </refsynopsisdiv> |
| 32 | <refsect1 id="parameters"><title>Parameters</title> |
| 33 | <variablelist> |
| 34 | <varlistentry> |
| 35 | <term><parameter>target</parameter></term> |
| 36 | <listitem> |
| 37 | <para> |
| 38 | Must be <constant>GL_CONVOLUTION_2D</constant>. |
| 39 | </para> |
| 40 | </listitem> |
| 41 | </varlistentry> |
| 42 | <varlistentry> |
| 43 | <term><parameter>internalformat</parameter></term> |
| 44 | <listitem> |
| 45 | <para> |
| 46 | The internal format of the convolution filter kernel. |
| 47 | The allowable values are |
| 48 | <constant>GL_ALPHA</constant>, |
| 49 | <constant>GL_ALPHA4</constant>, |
| 50 | <constant>GL_ALPHA8</constant>, |
| 51 | <constant>GL_ALPHA12</constant>, |
| 52 | <constant>GL_ALPHA16</constant>, |
| 53 | <constant>GL_LUMINANCE</constant>, |
| 54 | <constant>GL_LUMINANCE4</constant>, |
| 55 | <constant>GL_LUMINANCE8</constant>, |
| 56 | <constant>GL_LUMINANCE12</constant>, |
| 57 | <constant>GL_LUMINANCE16</constant>, |
| 58 | <constant>GL_LUMINANCE_ALPHA</constant>, |
| 59 | <constant>GL_LUMINANCE4_ALPHA4</constant>, |
| 60 | <constant>GL_LUMINANCE6_ALPHA2</constant>, |
| 61 | <constant>GL_LUMINANCE8_ALPHA8</constant>, |
| 62 | <constant>GL_LUMINANCE12_ALPHA4</constant>, |
| 63 | <constant>GL_LUMINANCE12_ALPHA12</constant>, |
| 64 | <constant>GL_LUMINANCE16_ALPHA16</constant>, |
| 65 | <constant>GL_INTENSITY</constant>, |
| 66 | <constant>GL_INTENSITY4</constant>, |
| 67 | <constant>GL_INTENSITY8</constant>, |
| 68 | <constant>GL_INTENSITY12</constant>, |
| 69 | <constant>GL_INTENSITY16</constant>, |
| 70 | <constant>GL_R3_G3_B2</constant>, |
| 71 | <constant>GL_RGB</constant>, |
| 72 | <constant>GL_RGB4</constant>, |
| 73 | <constant>GL_RGB5</constant>, |
| 74 | <constant>GL_RGB8</constant>, |
| 75 | <constant>GL_RGB10</constant>, |
| 76 | <constant>GL_RGB12</constant>, |
| 77 | <constant>GL_RGB16</constant>, |
| 78 | <constant>GL_RGBA</constant>, |
| 79 | <constant>GL_RGBA2</constant>, |
| 80 | <constant>GL_RGBA4</constant>, |
| 81 | <constant>GL_RGB5_A1</constant>, |
| 82 | <constant>GL_RGBA8</constant>, |
| 83 | <constant>GL_RGB10_A2</constant>, |
| 84 | <constant>GL_RGBA12</constant>, or |
| 85 | <constant>GL_RGBA16</constant>. |
| 86 | </para> |
| 87 | </listitem> |
| 88 | </varlistentry> |
| 89 | <varlistentry> |
| 90 | <term><parameter>x</parameter></term> |
| 91 | <term><parameter>y</parameter></term> |
| 92 | <listitem> |
| 93 | <para> |
| 94 | The window space coordinates of the lower-left coordinate of the |
| 95 | pixel array to copy. |
| 96 | </para> |
| 97 | </listitem> |
| 98 | </varlistentry> |
| 99 | <varlistentry> |
| 100 | <term><parameter>width</parameter></term> |
| 101 | <listitem> |
| 102 | <para> |
| 103 | The width of the pixel array to copy. |
| 104 | </para> |
| 105 | </listitem> |
| 106 | </varlistentry> |
| 107 | <varlistentry> |
| 108 | <term><parameter>height</parameter></term> |
| 109 | <listitem> |
| 110 | <para> |
| 111 | The height of the pixel array to copy. |
| 112 | </para> |
| 113 | </listitem> |
| 114 | </varlistentry> |
| 115 | </variablelist> |
| 116 | </refsect1> |
| 117 | <refsect1 id="description"><title>Description</title> |
| 118 | <para> |
| 119 | <function>glCopyConvolutionFilter2D</function> defines a two-dimensional convolution filter kernel with pixels |
| 120 | from the current <constant>GL_READ_BUFFER</constant> (rather than from main memory, |
| 121 | as is the case for <citerefentry><refentrytitle>glConvolutionFilter2D</refentrytitle></citerefentry>). |
| 122 | </para> |
| 123 | <para> |
| 124 | The screen-aligned pixel rectangle with lower-left corner at (<parameter>x</parameter>,\ <parameter>y</parameter>), |
| 125 | width <parameter>width</parameter> and height <parameter>height</parameter> |
| 126 | is used to define the convolution filter. If any pixels within this |
| 127 | region are |
| 128 | outside the window that is associated with the GL context, the |
| 129 | values obtained for those pixels are undefined. |
| 130 | </para> |
| 131 | <para> |
| 132 | The pixels in the rectangle are processed |
| 133 | exactly as if <citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry> had been called with <emphasis>format</emphasis> |
| 134 | set to RGBA, but the process stops just before final conversion. |
| 135 | The R, G, B, and A components of each pixel are next scaled by the four |
| 136 | 2D <constant>GL_CONVOLUTION_FILTER_SCALE</constant> parameters and biased by the |
| 137 | four 2D <constant>GL_CONVOLUTION_FILTER_BIAS</constant> parameters. |
| 138 | (The scale and bias parameters are set by <citerefentry><refentrytitle>glConvolutionParameter</refentrytitle></citerefentry> |
| 139 | using the <constant>GL_CONVOLUTION_2D</constant> target and the names |
| 140 | <constant>GL_CONVOLUTION_FILTER_SCALE</constant> and <constant>GL_CONVOLUTION_FILTER_BIAS</constant>. |
| 141 | The parameters themselves are vectors of four values that are applied to red, |
| 142 | green, blue, and alpha, in that order.) |
| 143 | The R, G, B, and A values are not clamped to [0,1] at any time during this |
| 144 | process. |
| 145 | </para> |
| 146 | <para> |
| 147 | Each pixel is then converted to the internal format specified by |
| 148 | <parameter>internalformat</parameter>. |
| 149 | This conversion simply maps the component values of the pixel (R, G, B, |
| 150 | and A) to the values included in the internal format (red, green, blue, |
| 151 | alpha, luminance, and intensity). The mapping is as follows: |
| 152 | </para> |
| 153 | <para> |
| 154 | </para> |
| 155 | <informaltable frame="topbot"> |
| 156 | <tgroup cols="7" align="left"> |
| 157 | <colspec colwidth="3*"/> |
| 158 | <colspec colwidth="1*" align="center"/> |
| 159 | <colspec colwidth="1*" align="center"/> |
| 160 | <colspec colwidth="1*" align="center"/> |
| 161 | <colspec colwidth="1*" align="center"/> |
| 162 | <colspec colwidth="1.7*" align="center"/> |
| 163 | <colspec colwidth="1.7*" align="center"/> |
| 164 | <thead> |
| 165 | <row> |
| 166 | <entry rowsep="1" align="left"><emphasis role="bold"> |
| 167 | Internal Format |
| 168 | </emphasis></entry> |
| 169 | <entry rowsep="1" align="center"><emphasis role="bold"> |
| 170 | Red |
| 171 | </emphasis></entry> |
| 172 | <entry rowsep="1" align="center"><emphasis role="bold"> |
| 173 | Green |
| 174 | </emphasis></entry> |
| 175 | <entry rowsep="1" align="center"><emphasis role="bold"> |
| 176 | Blue |
| 177 | </emphasis></entry> |
| 178 | <entry rowsep="1" align="center"><emphasis role="bold"> |
| 179 | Alpha |
| 180 | </emphasis></entry> |
| 181 | <entry rowsep="1" align="center"><emphasis role="bold"> |
| 182 | Luminance |
| 183 | </emphasis></entry> |
| 184 | <entry rowsep="1" align="center"><emphasis role="bold"> |
| 185 | Intensity |
| 186 | </emphasis></entry> |
| 187 | </row> |
| 188 | </thead> |
| 189 | <tbody> |
| 190 | <row> |
| 191 | <entry align="left"> |
| 192 | <constant>GL_ALPHA</constant> |
| 193 | </entry> |
| 194 | <entry align="center"> |
| 195 | </entry> |
| 196 | <entry align="center"> |
| 197 | </entry> |
| 198 | <entry align="center"> |
| 199 | </entry> |
| 200 | <entry align="center"> |
| 201 | A |
| 202 | </entry> |
| 203 | <entry align="center"> |
| 204 | </entry> |
| 205 | <entry align="center"> |
| 206 | |
| 207 | </entry> |
| 208 | </row> |
| 209 | <row> |
| 210 | <entry align="left"> |
| 211 | <constant>GL_LUMINANCE</constant> |
| 212 | </entry> |
| 213 | <entry align="center"> |
| 214 | </entry> |
| 215 | <entry align="center"> |
| 216 | </entry> |
| 217 | <entry align="center"> |
| 218 | </entry> |
| 219 | <entry align="center"> |
| 220 | </entry> |
| 221 | <entry align="center"> |
| 222 | R |
| 223 | </entry> |
| 224 | <entry align="center"> |
| 225 | |
| 226 | </entry> |
| 227 | </row> |
| 228 | <row> |
| 229 | <entry align="left"> |
| 230 | <constant>GL_LUMINANCE_ALPHA</constant> |
| 231 | </entry> |
| 232 | <entry align="center"> |
| 233 | </entry> |
| 234 | <entry align="center"> |
| 235 | </entry> |
| 236 | <entry align="center"> |
| 237 | </entry> |
| 238 | <entry align="center"> |
| 239 | A |
| 240 | </entry> |
| 241 | <entry align="center"> |
| 242 | R |
| 243 | </entry> |
| 244 | <entry align="center"> |
| 245 | |
| 246 | </entry> |
| 247 | </row> |
| 248 | <row> |
| 249 | <entry align="left"> |
| 250 | <constant>GL_INTENSITY</constant> |
| 251 | </entry> |
| 252 | <entry align="center"> |
| 253 | </entry> |
| 254 | <entry align="center"> |
| 255 | </entry> |
| 256 | <entry align="center"> |
| 257 | </entry> |
| 258 | <entry align="center"> |
| 259 | </entry> |
| 260 | <entry align="center"> |
| 261 | </entry> |
| 262 | <entry align="center"> |
| 263 | R |
| 264 | </entry> |
| 265 | </row> |
| 266 | <row> |
| 267 | <entry align="left"> |
| 268 | <constant>GL_RGB</constant> |
| 269 | </entry> |
| 270 | <entry align="center"> |
| 271 | R |
| 272 | </entry> |
| 273 | <entry align="center"> |
| 274 | G |
| 275 | </entry> |
| 276 | <entry align="center"> |
| 277 | B |
| 278 | </entry> |
| 279 | <entry align="center"> |
| 280 | </entry> |
| 281 | <entry align="center"> |
| 282 | </entry> |
| 283 | <entry align="center"> |
| 284 | |
| 285 | </entry> |
| 286 | </row> |
| 287 | <row> |
| 288 | <entry align="left"> |
| 289 | <constant>GL_RGBA</constant> |
| 290 | </entry> |
| 291 | <entry align="center"> |
| 292 | R |
| 293 | </entry> |
| 294 | <entry align="center"> |
| 295 | G |
| 296 | </entry> |
| 297 | <entry align="center"> |
| 298 | B |
| 299 | </entry> |
| 300 | <entry align="center"> |
| 301 | A |
| 302 | </entry> |
| 303 | <entry align="center"> |
| 304 | </entry> |
| 305 | <entry align="center"> |
| 306 | |
| 307 | </entry> |
| 308 | </row> |
| 309 | </tbody> |
| 310 | </tgroup> |
| 311 | </informaltable> |
| 312 | <para> |
| 313 | The red, green, blue, alpha, luminance, and/or intensity components of |
| 314 | the resulting pixels are stored in floating-point rather than integer |
| 315 | format. |
| 316 | </para> |
| 317 | <para> |
| 318 | Pixel ordering is such that lower x screen coordinates correspond to |
| 319 | lower <emphasis>i</emphasis> filter image coordinates, and lower y screen coordinates |
| 320 | correspond to lower <emphasis>j</emphasis> filter image coordinates. |
| 321 | </para> |
| 322 | <para> |
| 323 | Note that after a convolution is performed, the resulting color |
| 324 | components are also scaled by their corresponding |
| 325 | <constant>GL_POST_CONVOLUTION_c_SCALE</constant> parameters and biased by their |
| 326 | corresponding <constant>GL_POST_CONVOLUTION_c_BIAS</constant> parameters (where |
| 327 | <emphasis>c</emphasis> takes on the values <emphasis role="bold">RED</emphasis>, <emphasis role="bold">GREEN</emphasis>, <emphasis role="bold">BLUE</emphasis>, and |
| 328 | <emphasis role="bold">ALPHA</emphasis>). |
| 329 | These parameters are set by <citerefentry><refentrytitle>glPixelTransfer</refentrytitle></citerefentry>. |
| 330 | </para> |
| 331 | </refsect1> |
| 332 | <refsect1 id="notes"><title>Notes</title> |
| 333 | <para> |
| 334 | <function>glCopyConvolutionFilter2D</function> is present only if <code>ARB_imaging</code> is returned when <citerefentry><refentrytitle>glGetString</refentrytitle></citerefentry> |
| 335 | is called with an argument of <constant>GL_EXTENSIONS</constant>. |
| 336 | </para> |
| 337 | </refsect1> |
| 338 | <refsect1 id="errors"><title>Errors</title> |
| 339 | <para> |
| 340 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not |
| 341 | <constant>GL_CONVOLUTION_2D</constant>. |
| 342 | </para> |
| 343 | <para> |
| 344 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>internalformat</parameter> is not one of the |
| 345 | allowable values. |
| 346 | </para> |
| 347 | <para> |
| 348 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>width</parameter> is less than zero or greater |
| 349 | than the maximum supported value. |
| 350 | This value may be queried with <citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry> |
| 351 | using target <constant>GL_CONVOLUTION_2D</constant> and name |
| 352 | <constant>GL_MAX_CONVOLUTION_WIDTH</constant>. |
| 353 | </para> |
| 354 | <para> |
| 355 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>height</parameter> is less than zero or greater |
| 356 | than the maximum supported value. |
| 357 | This value may be queried with <citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry> |
| 358 | using target <constant>GL_CONVOLUTION_2D</constant> and name |
| 359 | <constant>GL_MAX_CONVOLUTION_HEIGHT</constant>. |
| 360 | </para> |
| 361 | <para> |
| 362 | <constant>GL_INVALID_OPERATION</constant> is generated if <function>glCopyConvolutionFilter2D</function> is executed |
| 363 | between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding |
| 364 | execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>. |
| 365 | </para> |
| 366 | </refsect1> |
| 367 | <refsect1 id="associatedgets"><title>Associated Gets</title> |
| 368 | <para> |
| 369 | <citerefentry><refentrytitle>glGetConvolutionParameter</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glGetConvolutionFilter</refentrytitle></citerefentry> |
| 370 | </para> |
| 371 | </refsect1> |
| 372 | <refsect1 id="seealso"><title>See Also</title> |
| 373 | <para> |
| 374 | <citerefentry><refentrytitle>glConvolutionFilter2D</refentrytitle></citerefentry>, |
| 375 | <citerefentry><refentrytitle>glConvolutionParameter</refentrytitle></citerefentry>, |
| 376 | <citerefentry><refentrytitle>glPixelTransfer</refentrytitle></citerefentry> |
| 377 | </para> |
| 378 | </refsect1> |
| 379 | <refsect1 id="Copyright"><title>Copyright</title> |
| 380 | <para> |
| 381 | Copyright <trademark class="copyright"></trademark> 1991-2006 |
| 382 | Silicon Graphics, Inc. This document is licensed under the SGI |
| 383 | Free Software B License. For details, see |
| 384 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. |
| 385 | </para> |
| 386 | </refsect1> |
| 387 | </refentry> |